Library

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Electronic Resource  (45)
  • Loose Leaf
  • 2010-2014
  • 1980-1984  (31)
  • 1960-1964  (14)
  • 1890-1899
  • 1870-1879
  • Heterocycles
  • Synthetic methods
Material
  • Electronic Resource  (45)
  • Loose Leaf
Years
Year
  • 1
    ISSN: 1434-4475
    Keywords: Cinnamonitriles ; Cyanoethylations ; Heterocycles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung 3-Antipyrinyl-5-aminopyrazol (1) reagierte mit Acrylnitril zu 5-Amino-1-β-cyanoethyl-3-antipyrinylpyrazol (2).2 konnte ebenfalls aus der Reaktion von β-Cyanethylhydrazin (3) und Verbindung4 erhalten werden.2 wurde mittels Essigsäure-Salzsäure glatt zu 2-Antipyrinyl-4,5,6,7-tetrahydropyrazolo[1,5-a]-pyrimidin-5-on (5) cyclisiert.5 konnte auch aus der Reaktion von1 mit Methylacrylat erhalten werden. Die Reaktion von1 mit Zimtsäurenitrilderivaten7 a–e ergab die Pyrazolo[1,5-a]pyrimidin-Derivate9,11 und12.
    Notes: Abstract 3-Antipyrinyl-5-aminopyrazole (1) reacted with acrylonitrile to afford 5-amino-1-β-cyanoethyl-3-antipyrinylpyrazole (2). Compound2 could also be obtained from the reaction of β-cyanoethylhydrazine (3) and compound4.2 was readily cyclized into 2-antipyrinyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-5-one (5) by acetic-hydrochloric acid.5 could be also obtained from the reaction of1 and methyl acrylate. The reaction of1 and cinnamonitrile derivatives7 a–e resulted in the formation of pyrazolo[1,5-a]pyrimidine derivatives9,11 and12.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 115 (1984), S. 757-763 
    ISSN: 1434-4475
    Keywords: Heterocycles ; Synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die 5-Alkyl-5,6-dihydrobenzimidazo[2,1 -h]pteridin-2,4(1H,3H)-dione4 a-d wurden mittels Kondensation von 2-(Alkylaminomethyl)benzimidazolidhydrochloriden1 a–d mit 5-Brombarbitursäure (2) dargestellt. In ähnlicher Weise wurden die 5-Alkyl-5,6-dihydro-4a-nitrobenzimidazo[2,1 -h]pteridin-2,4(3H,4aH)-dione10 a–d über die Kondensation von1 a–d mit 5-Brom-5-nitrobarbitursäure (8) und nachfolgender Cyclisierung der intermediären 5-[(Benzimidazol-2-ylmethyl)alkylamino]-5-nitrobarbitursäuren9 a–d mit 5% NaOH dargestellt. Die thermische Cyclisierung der Produkte9 a–d wurde ebenfalls untersucht. Die Verbindungen wurden mittels Elementaranalyse, IR und PMR charakterisiert.
    Notes: Abstract 5-Alkyl-5,6-dihydrobenzimidazo[2,1 -h]pteridine-2,4(1H,3H)-diones (4 a–d) have been synthesised by the condensation of 2-(alkyl-aminomethyl)benzimidazole dihydrochloride (1 a–d) with 5-bromobarbituric acid (2). Similarly, 5-alkyl-5,6-dihydro-4 a-nitrobenzimidazo[2,1 -h] pteridine-2,4(3H,4aH)-diones (10 a–d) have also been synthesised by the condensation of1 a–d with 5-bromo-5-nitrobarbituric acid (8) followed by cyclisation of the intermediate 5-[(benzimidazol-2-ylmethyl)alkylamino]-5-nitrobarbituric acid (9 a–d) with 5% NaOH. Thermal cyclisation of the intermediates9 a–d have also been studied. Methylation of the compound10 a has been carried out with CH3I and K2CO3 usingD M F as solvent to confirm cyclisation. The structures are supported by elemental analyses, IR and PMR spectra.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 23 (1984), S. 539-556 
    ISSN: 0570-0833
    Keywords: Cycloaddition ; Synthetic methods ; Cobalt catalysts ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dicarbonyl (η5-cyclopentadienyl)cobalt functions as a matrix on which a variety of unsaturated organic substrates undergo mutual bond formation. In this way α,ω-diynes cocyclize with monoalkynes to give annelated benzenes, while o-diethynylbenzenes furnish biphenylenes, and α,ω-enynes lead to the formation of complexed bi-and tricyclic dienes. Nitriles cocyclize with two alkynyl groups to give pyridines and other heterocycles, isocyanates allow access to annelated 2-pyridones, and incorporation of carbon monoxide provides complexed cyclopentadienones. In many cases remarkable chemo-, regio-, and stereoselectivity are observed, partially facilitated by use of the trimethylsilyl substituent as a controlling group. The scope and level of maturity of the method are demonstrated by the synthesis of a series of hitherto inaccessible, novel, and theoretically interesting molecules, and by its utilization in several unique approaches to a variety of natural products, e.g. protoberberines, steroids, vitamin B6, and camptothecin.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 23 (1984), S. 556-569 
    ISSN: 0570-0833
    Keywords: Addition ; Alkoxy carbonyl compounds ; Synthetic methods ; Chelates ; Stereoselectivity ; Reaction mechanisms ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of C-nucleophiles such as Grignard reagents or enolates to chiral α- or β-alkoxy aldehydes or ketones creates a new center of chirality and is therefore diastereogenic. In order to control stereoselectivity, two strategies have been developed: (1) Use of Lewisacidic reagents which form intermediate chelates, these being attacked stereoselectively from the less hindered side (chelation control); (2) use of reagents incapable of chelation, stereoselective attack being governed by electronic and/or steric factors (non-chelation control). Generally, the two methods lead to the opposite sense of diastereoselectivity. It is possible to predict the outcome by careful choice of organometallic reagents containing elements such as Li, Mg, B, Si, Sn, Cu, Zn, or Ti.For corrigendum see DOI:10.1002/anie.198407461
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 23 (1984), S. 579-586 
    ISSN: 0570-0833
    Keywords: Rearrangement ; Synthetic methods ; Mercury ; Palladium ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mercury(II) and palladium(II) salts have found broad applications as catalysts for [3,3]-sigmatropic rearrangements leading to formation of C—O, C—N, C—S, and C—C σ bonds. Increases in reaction rate are often very large (1010 - 1014 at 1 M catalyst concentration) and allow many previously difficult transformations to be conducted at or near room temperature, often with attendant increases in stereoselectivity and decreases in by-product formation. The mechanism of these catalyzed transformations is briefly discussed, and evidence is summarized to suggest that many follow a cyclization-induced rearrangement mechanism.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 23 (1984), S. 570-578 
    ISSN: 0570-0833
    Keywords: Asymmetric catalysis ; Catalysis ; Enantioselectivity ; Reduction ; Ketones ; Synthetic methods ; Biotechnology ; Alcohols ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Microbial asymmetric reduction of ketones is a method widely used for the preparation of chiral alcohols. The present progress report deals with the basic concepts that govern enantioselectivity of enzymes and intact cells. Strategies to control the stereochemical course of microbial reductions of carbonyl compounds and the relationship of substrate structure to enantioselectivity are considered.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 23 (1984), S. 587-608 
    ISSN: 0570-0833
    Keywords: Carbene ligands ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transition metals are finding increasing use in organic synthesis on the borderline between “organic” and “inorganic” chemistry. Advantage is taken thereby of the fact that metal-induced CC bond formation often takes place with remarkable selectivity. The rapid development that has taken place in this area of chemistry is clearly demonstrated by the carbene complexes, examples of which are now known for almost all transition elements, and which have transformed from organometallic curiosities into synthetically useful reagents in less than two decades since the first studies of E. O. Fischer. They are not only suitable as carbene-transfer agents but also undergo interesting cycloadditions with other ligands in the co-ligand sphere. Their manipulation requires techniques no more complicated than those for Grignard reactions. Thus, carbene complexes can also be used in the synthesis of natural products such as vitamins or antibiotics.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 23 (1984), S. 1-19 
    ISSN: 0570-0833
    Keywords: Cycloaddition ; Allyl cations ; Cations ; Synthetic methods ; Cycloheptanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of allyl cations and 1,3-dienes affords seven-, five-, and six -membered rings as well as products of electrophilic substitution and linear 1:1-adducts. In this review article, preparative and mechanistic advances are summarized with special emphasis on the synthesis of seven-membered carbocycles. For the first time, a comprehensive mechanistic description is presented: Three classes A, B, and C correlate product type and stereochemistry with the nucleophilicity of the diene, the electrophilicity of the allyl cation intermediate, and the donor capacity of the group Y attached to the central carbon of the allylic moiety. The problem “allylic resonance versus nucleophilic participation of Y” is discussed and experimental evidence is adduced for some participation of Y as a function of its nucleophilicity. For cyclopentenyl cations, enhanced charge separation and electrophilicity are postulated, even when Y is a good donor, due to the structurally enforced polarity of the π-allyl system.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 23 (1984), S. 413-419 
    ISSN: 0570-0833
    Keywords: α-Arylalkanoic acids ; 1,2-Aryl shift ; Synthetic methods ; Anti-inflammatory agents ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: α-Arylalkanoic acids have acquired importance as anti-inflammatory agents and are now in great demand on the pharmaceutical front. Hence, the need has arisen for new and improved, economical synthetic procedures suitable for their preparation and manufacture on an industrial scale. For many years the synthetic approach to this class of compounds was restricted to the Willgerodt and Darzen reactions. More recently, several methods have been developed which are based on the 1,2-aryl shift in acetals of α-functionalized alkyl aryl ketones. This new approach starts from the oxythallation of alkyl aryl ketones first described by Taylor and McKillop in 1971. Asymmetric syntheses of some important arylakanoic acids have also been developed on this basis. The highly toxic thallium salts may be replaced, inter alia, by catalytically effective metal salts.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 0570-0833
    Keywords: Pyrylium salts ; Pyridinium salts ; Synthetic methods ; Amines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first pyrylium salt was isolated some 80 years ago, yet up to the 1950s only moderate interest was taken in the preparation, properties and uses of such salts. However, the past thirty years has seen a phenomenal growth in the literature pertinent to this area of chemistry: the importance of pyrylium salts as intermediates has been realized. They are readily prepared by a variety of generally applicable routes, and they are highly reactive towards nucleophiles. Together, this enables the convenient synthesis of a great variety of acyclic and heterocyclic compounds. We have used highly substituted pyrylium salts for the two-step conversion of the amino group in alkylamines RNH2 into numerous other functionalities. In the first step, the pyrylium salts are converted with the amines into N-substituted pyridinium salts, which, in the second step, react with Nu⊖ to give the desired products RNu. In some cases the R moiety is also changed, e.g. by elimination. Studies of the reactions of these pyridinium salts have allowed interesting insights into the mechanisms of nucleophilic substitution, in addition to rendering aliphatic amines important synthetic intermediates. Thus, the method complements the diazotization procedure for the transformation of arylamines.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 23 (1984), S. 847-876 
    ISSN: 0570-0833
    Keywords: Prostaglandins ; Three-component coupling ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The role played by prostaglandins (PGs) in the human body is bewitching. Following the elucidation of their structures in the early 1960s, tremendous efforts were made for the realization of an efficient chemical synthesis, since a sufficient supply of such very rare, naturally occurring local hormones relies solely on their total synthesis. Of the many synthetic routes described in the literature, the majority of which are linear or sequential in nature, the Corey synthesis is perhaps the most versatile; so far more than 5000 prostaglandin analogues have been prepared and have been tested biologically. Some natural prostaglandins and their analogues are already in clinical use. In view of the continuing expansion of this field, we have been fascinated with the concept of developing a highly convergent entry to prostaglandins based on a new strategy. The discovery of a highly enantioselective method for the reduction of prochiral ketones and the elaboration of a procedure for double vicinal CC-coupling with enones have enabled a one-pot synthesis of the complete prostaglandin skeleton by linking a chiral 4-oxygenated 2-cyclopentenone unit and two side-chain blocks. This approach is efficient and flexible and allows the direct production of all the naturally occuring prostaglandins and a wide spectrum of analogues.
    Additional Material: 10 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 12
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 23 (1984), S. 876-889 
    ISSN: 0570-0833
    Keywords: Synthetic methods ; Cycloaddition ; Diels-Alder reaction ; Ene reaction ; Asymmetric synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rapidly accumulating evidence shows the value of asymmetric Diels-Alder and ene reactions for the syntheses of enantiomerically pure molecules. This article presents a systematic and critical treatment of various stereoface-differentiating principles, including very recent spectacular advances. The chiral information is mainly provided by covalently bound auxiliaries, some of which are crystalline, inexpensive, and readily available from naturally occurring monoterpenes, hydroxy acids, amino acids, steroids, and sugars. Non-destructive transfer of chirality leads to the efficient creation of up to four chiral centers with predictable relative and absolute configurations. Regenerative cleavage of the auxilary group from the diastereomerically pure adducts furnishes a range of polyfunctional, optically pure building blocks. Their synthetic potential is illustrated by strategic applications to the syntheses of physiologically interesting, chiral natural products such as prostaglandins, antibiotics, terpenoids, shikimic acid, alkaloids, and kainoids.
    Additional Material: 10 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 13
    ISSN: 0570-0833
    Keywords: Homoaldol reaction ; Stereoselectivity ; Synthetic methods ; Regioselectivity ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Even today, there are conspicuous gaps in the register of organic synthetic methods. Thus, numerous types of homoenolate reagents are listed; yet no generally applicable method for the homologue of the aldol addition, viz. the homoaldol addition, is to be found. The methods documented up to 1980 offer only singular solutions, and, moreover, are not stereoselective. The present article gives an overview of the existing possibilities and then describes how the gap can be closed by using a new class of homoenolate reagents: 2-alkenyl esters of N,N-diisopropylcarbamic acid are lithiated and the resulting allyllithium compounds tailored to high regio- and diastereoselectivity in addition reactions to the carbonyl group via metal exchange. Altogether, the homoaldol reactions now offer a general and reliable, highly stereoselective entry to γ-hydroxycarbonyl compounds, whereby the C(β)—C(γ) bond is formed. Furthermore, it is demonstrated how problems associated with the application of allyl anions as synthetic reagents can be solved today.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 114 (1983), S. 219-225 
    ISSN: 1434-4475
    Keywords: Cyanine dyes ; Dipyrazolylmethanes ; Heterocycles ; N-15-NMR ; O-17-NMR ; Phenazon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The 4-pyrazoline-3-one1 reacts with 4-dimethylaminobenzaldehyde to yield the stable asymmetric cyanine dye2b which reacts with1 to give the colorless (aryl) (dipyrazolyl) methane3b. Using aldehydes with less cationstabilizing groups the polymethines2 are not isolated but only the methanes3. The structures of2b and3 are discussed by1 H,13C and Hetero NMR spectra.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 114 (1983), S. 339-342 
    ISSN: 1434-4475
    Keywords: Heterocycles ; Infrared ; 1H-NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung 3-Methyl-6H-[1,2,4]triazolo[4′ ,3′ : 4,5] [1,3,4]thiadiazolo[2,3-b]chinazolin-6-on (6) wurde mittels Kondensation von Isatoesäureanhydrid (1) mit 4-Amino-5-mercapto-3-methyl[1,2,4]triazol (2) und anschließender Cyclisierung von Zwischenverbindung3 mit POCl3 und PCl3 dargestellt. Als Alternative konnte6 auch über die Kondensation von 3-Amino-2-mercapto-3H-chinazolin-4-on (7) mitN-Carbethoxyhydrazin in Gegenwart von HCl und anschließender Cyclisierung der Zwischenverbindung8 mit Essigsäure synthetisiert werden. Die Strukturen der Verbindungen wurden mittels IR,1H-NMR und Mikroanalyse nachgewiesen.
    Notes: Abstract 3-Methyl-6H-[1,2,4]triazolo[4′,3′: 4,5] [1,3,4]thiadiazolo[2,3-b]quinazolin-6-one (6) has been synthesized by the condensation of isatoic anhydride (1) with 4-amino-5-mercapto-3-methyl-[1,2,4]triazole (2) and final cyclisation of the intermediate3 with POCl3 and PCl3. Alternatively6 could also be synthesized by the condensation of 3-amino-2-mercapto-3H-quinazolin-4-one (7) withN-carbethoxy hydrazine in presence of hydrochloric acid and final cyclisation of the intermediate8 with acetic acid. The structures have been confirmed on the basis of IR, PMR and analytical results.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 16
    ISSN: 0570-0833
    Keywords: Nucleophilic reactions ; Synthetic methods ; Selectivity ; Organotitanium compounds ; Organozirconium compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of carbanionic organometallic compounds (usually RLi or RMgX) to a carbonyl group - a key step in numerous syntheses - is not always straightforward. Depending on the substrate, various complications and problems may arise, but in many cases these can be remedied by addition of (RO)3TiCl, (RO)3ZrCl or (R2N)3TiX to the classic lithium and Grignard reagents. This usually leads to formation of stable organo-titanium and -zirconium compounds which react highly selectively with carbonyl groups. For example, CH3Ti(OiPr)3 reacts five orders of magnitude faster with benzaldehyde than with acetophenone at room temperature; reagents of the type RTi(OiPr)3 add smoothly to nitro-, ido-, or cyano-subsituted benzaldehyde, and the reactions may be performed in chlorinated solvents or acetonitrile; the zirconium analogues have particularly low basicity and add in high yield to α- and β-tetralones or to substrates containing a nitroaldol group; the inclusion of chiral OR* groups gives enantioselective reagents (up to 90% ee); allylic (RO3)Ti- derivatives react only at the more highly substituted carbon atom and, in addition, react diastereoselectively (up to 98% ds) with unsymmetrical ketones. Finally, titanium reagents have also been found to effect novel transformations such as direct geminal dialkylation (C=O→CMe2) and alkylative amination [C=O→CR(NR2′)]. The modification and finetuning (“taming”) of carbonyl reactivity obtainable by use of the new reagents is not dearly bought; starting materials are the cheap and harmless “titanates”, “zirconates” and the corresponding tetrachlorides.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 17
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 22 (1983), S. 171-190 
    ISSN: 0570-0833
    Keywords: 1,4-Diazines ; Pyrazine ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In chemical research attention is increasingly being focussed on composite “complex” systems with special properties and functions. As components of such systems 1,4-diazines are steadily gaining in popularity. Here, 1,4-diazines means pyrazine and its derivatives as well as compounds with partial pyrazine structure; examples are quinoxaline, phenazine, pteridine, flavin and their derivatives. All these compounds are characterized by a low lying unoccupied π-molecular orbital and by the ability to act as bridging ligand. Due to these two properties 1,4-diazines, and especially their parent compound pyrazine, possess a characteristic reactivity. 1,4-Diazines may be employed to study inter- and intramolecular electron transfer in organic, inorganic and biochemical reactions. In the redox system of 1,4-diazines the paramagnetic 7π-electron intermediate exhibits exceptional stability, whereas the 1,4-dihydro-1,4-diazines with 8π-electrons in a six-membered ring are not generally accessible due to their potential antiaromaticity and their large excess of π electrons. Its inherent bifunctionality and the low lying unoccupied molecular orbital permit pyrazine to form coordination polymers having unusual electrical and magnetic properties. Finally, the phenomena observed for pyrazines may be used in the interpretation of the reactivity of naturally occurring 1,4-diazines, such as flavins and bioluminescent natural products.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 22 (1983), S. 337-350 
    ISSN: 0570-0833
    Keywords: Cyclization ; Chloroamines ; Alkenylamines ; Synthetic methods ; Heterocycles ; Free radicals ; Natural products ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Many N-chloroalkylamines with double bond(s) dissociate homolytically to give chlorine atoms and aminyl radicals which undergo intramolecular cyclization reactions. Here, the nature of the aminyl radicals (neutral, protonated, or complexed to metal salts) appears to be important. The reactivity varies strongly from one species to another, and their selectivities can be different towards addition, substitution, abstraction, or dimerization reactions. A good synthetic tool appears to be the “complexed radical”, which is generated under mild conditions. A variety of β-functionalized, substituted, fused, or bridged azaheterocycles with alkaloid part structures thus become easily accessible in high yields, in a regio- and, possibly, stereoselective manner. Many examples are discussed illustrating the synthetic possibilities, limitations, and mechanistic features of this cyclization process.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 19
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 22 (1983), S. 599-613 
    ISSN: 0570-0833
    Keywords: Complex reducing agents ; Reduction ; Sodium hydride ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Why do we hardly use the simplest and, at the same time, inexpensive reducing agent sodium hydride in organic chemistry? To this question the answer is invariably: “It is too basic”. In this progress report we describe work we have performed aimed at controlling the basicity of NaH using sodium alcoholates and metal salts. The complex reducing agents (CRA's) developed (symbolized NaH-RONa-MXn) allow organic halides, alkenes, alkynes and ketones to be reduced selectively. Highly regioselective 1,4- and 1,2-reductions of α,β-unsaturated ketones are easily performed using appropriate metal salts. Modified CRA's have proved to be excellent hydrosilylating reagents for carbonyl groups, non-pyrophoric heterogeneous hydrogenation catalysts, coupling reagents for aryl and vinyl halides, and reagents for the carbonylation of organic halides under very mild conditions. The study of these reactions opened up the field to phase-transfer-catalyzed photostimulated carbonylations as well as to SRN1 reactions of metalates.-Thus, starting from the simple sodium hydride a large number of useful reagents have become accessible.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 113 (1982), S. 1283-1297 
    ISSN: 1434-4475
    Keywords: Heterocycles ; Keto-enol-tautomerism ; Synthesis ; 2H-Thiopyrane-2-ones and -2-thiones, 4-alkylamino and 4-alkoxy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The tautomers 4-hydroxy-6,6-dimethyl-5,6-dihydro-2H-thiopyran-2-thione (4 a) and 2-mercapto-6,6-dimethyl-5,6-dihydro-4H-thiopyran-4-one (4 b) resp. were synthesized by hydrolysis of 4-amino-5,6-dihydro-2H-thiopyranthiones6,8. On methylation of4 a,b only the S-methyl product7 is formed. Hydrolysis of 4-amino-2-methylthiothiopyranyliden iodides11 leads—depending on the amino group of11—either to the thiopyranone7 or to the 4-imino-thiopyranes12 and to β-amino-α,β,γ,δ-unsaturated-methyldithio carboxylates13. On reaction of4 a,b with hydrogenperoxyd the tautomers 4-hydroxy-5,6-dihydro-2H-thiopyran-2-one5 a and 5,6-dihydro-2H-thiopyran-2,4(3H)diones5 b resp. are formed.4 a,b and5 a,b undergo an aminolysis with prim. and sec. amines to the corresponding 4-amino-2H-thiopyran-2-thiones6,8 and -ones10 resp. On heating in alcohols the 4-alkoxy-thiopyrane-2-thiones and -ones9,14 are formed from4 a,b and5 a,b resp.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 21
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 113 (1982), S. 1145-1150 
    ISSN: 1434-4475
    Keywords: Heterocycles ; Synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Zur Synthese von 4H,6H-[1,3,4]thiadiazino[2,3-b]chinazolin-6-on (6a) wurde die Kondensation von 3-Amino-2-mercapto-3H-chinazolin-4-on (1) mit Allylbromid mit nachfolgender Behandlung mit Brom und Dehydrohalogenierung des bromierten Produktes4 mit ethanolischer Natronlauge herangezogen. Das zu6a isomere 2H,6H-Produkt6b wurde ebenfalls durch Kondensation von1 mit Bromaceton und nachfolgender Cyclisierung der Zwischenprodukte8 bzw.9 mit HBr oder H2SO4 erhalten. Die Strukturen wurden mittels IR und NMR abgesichert.
    Notes: Abstract 4H,6H-[1,3,4]Thiadiazino[2,3-b]quinazolin-6-one with a methyl group in position 3 (6a) has been synthesised by the condensation of 3-amino-2-mercapto-3H-quinazolin-4-one (1) with allyl bromide (2) followed by treatment with bromine and subsequent dehydrohalogenation of the brominated product (4) with ethanolic sodium hydroxide. Its isomeric 3-methyl-2H,6H-[1,3,4]thiadiazino[2,3-b]quinazolin-6-one (6b) has also been obtained by condensation of1 and bromoacetone (7) followed by cyclisation of the intermediates (8 or9) with hydrobromic acid or with concentrated sulphuric acid. The structures have been established on the basis of IR and PMR data.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 22
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 21 (1982), S. 36-49 
    ISSN: 0570-0833
    Keywords: Acyl cyanides ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Through improved and novel syntheses, acyl cyanides - especially aliphatic acyl cyanides - have become so readily accessible that numerous synthetic applications present themselves. The present review surveys the development of the chemistry of the acyl cyanides during the last 25 years. The syntheses and most important reaction possibilities of R—CO—CN are outlined in four large schemes: reactions of the CO- and CN-groups - in each case with preservation of the carbon skeletal framework - as well as acylations with cleavage of cyanide ions.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 23
    ISSN: 0570-0833
    Keywords: Heavy main-group elements ; Main group elements ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aside from elements of the 2nd row, and one element of the 3rd row of the periodic system - Si, P, S, and Se, respectively, whose organoelement groups such as Me3Si and Ph3P⊕ have proven useful in numerous organic syntheses - other elements of the 3rd as well as 4th and 5th row (Ge, As, Sn, Sb, Te, Pb, Bi) can also be used as components of synthetically useful organoelement groups, the elements As, Sn, and Pb, in particular, offering certain advntages over the others. Some of these organoelement groups are suitable equivalents for Li- or halogen-substituents attached to carbon; they stabilize carbanionic centers (minimum of this effect at the 3rd-row elements), and owing to their suitability as leaving groups in β-eliminations, also open up interesting synthetic possibilities. The thermally unduced syn- and silica-gel induced anti-elimination of Ph3Sn, Ph2Sb, Ph3Pb, together with β-OH, are novel. With the newly synthesized compounds PhnEl - Ch2 - Li (El = Sn, Pb, As, Sb, Bi) and other α- and β-lithiated RnEl- and Ph2As(O)-reagents such organoelement groups can be introduced into organic compounds and exploited in organic and organoelement synthesis.
    Additional Material: 13 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 24
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 21 (1982), S. 96-108 
    ISSN: 0570-0833
    Keywords: Lewis acids ; Alkylation ; Carbonyl compounds ; Synthetic methods ; Silyl enol ethers ; C-C coupling ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbonyl compounds undergo α-alkylation via the corresponding silyl enol ethers using SN1 active alkyl halides or acetates in the presence of Lewis acids. This methodology extends the scope of carbonyl chemistry considerably, since SN1 active alkylating agents are generally base sensitive and therefore unsuitable for reactions with enolate anions or nitrogen analogs. A prime example is the α-tert-alkylation of aldehydes, ketones and esters.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 25
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 112 (1981), S. 1187-1194 
    ISSN: 1434-4475
    Keywords: Heterocycles ; Knoevenagel reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Reaktion von Malodinitril mit Benzoylacetaniliden wurde untersucht. Die Struktur der dabei erhaltenen Verbindungen (2–4) wurde auf Basis der chemischen und spektroskopischen Eigenschaften zugeordnet.
    Notes: Abstract The reaction of benzoylacetanilides with malononitrile has been investigated. The structure of the compounds obtained (2, 3, 4) have been assigned on the basis of chemical properties and spectral data.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 26
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 112 (1981), S. 1083-1090 
    ISSN: 1434-4475
    Keywords: Heterocycles ; 1 H-NMR ; Stereochemistry ; Synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurde eine Reihe von 5,12a-Dihydro-6-alkyl/aryl-6H-benzothiazolo [3,2-c]-1,3-dioxolo[4,5-g]chinazoline, sowohl mitcis-als auchtrans-ständigen Wasserstoffatomen an Kohlenstoff 6 und 12a, synthetisiert. Ebenso wurden auch Verbindungen dieses Systems mit Thiazol an Position 6 hergestellt. Die Strukturen wurden mittels IR- und NMR-spektroskopischen Daten abgesichert.
    Notes: Abstract Some 5,12a-dihydro-6-alkyl/aryl-6H-benzothiazolo[3,2-c]-1,3-dioxolo [4,5-g]quinazolines withcis as well astrans stereochemistry of the hydrogens at carbon 6 and 12a have been synthesised. The synthesis of another series of compounds of the above system with thiazole ring at position 6 has also been accomplished. The structures have been established on the basis of IR and PMR data.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 27
    ISSN: 0570-0833
    Keywords: Hetero-1,3,5-hexatrienes ; Pericyclic reactions ; Photochemistry ; Cyclization ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heterosubstituted 1,3,5-hexatrienes undergo thermal and photochemical cyclizations, most of which can be viewed as pericyclic reactions. Numerous cyclizations of this type have been reported in the literature. This article presents a systematic account of such reactions, classified according to the number and nature of the heteroatoms.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 28
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 19 (1980), S. 947-973 
    ISSN: 0570-0833
    Keywords: Electrocyclic reactions ; Cyclization ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The principle of orbital control of pericyclic reactions has deepened our understanding of reaction phenomena and provided an excellent classification of these one-step processes. The electrocyclic reaction of the pentadienyl anion ⇌ cyclopentenyl anion type is relatively unimportant in all-carbon systems and has not even been verified in the case of the parent compound. In the heterocyclic series, however, where up to five C-atoms of the pentadienyl anion are replaced by heteroatoms, a multitude of ring closures and ring openings find their ordering principle in the mentioned electrocyclic reaction. The replacement of the carbon atoms by heteroatoms can take place isoinically, i. e., with retention of the anionic character, or isoelectronically. An isoelectronic replacement of CR2 in position 1 by NR2 OR, and or CR in position 3 by NR or O leads to a charge-free resonance structure for the open-chain species; the migration of the charge during the electrocyclization results in a correlation with a cyclic zwitterion. Conversely, isoelectronic exchange of CR in position 2 by NR or O produces a conjugated 1,3-dipole, which cyclizes to a charge-free unsaturated five-membered ring. Twofold isoelectronic exchange allows the whole process to take place in a cation. Selected examples are to shed light on the classification and the thermodynamics of this electrocyclic reaction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 29
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 19 (1980), S. 762-779 
    ISSN: 0570-0833
    Keywords: Azoalkanes ; Synthetic methods ; Strained molecules ; Cage compounds ; Polycycles ; Photochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal or photochemical denitrogenation of azoalkanes constitutes an effective and convenient method for the preparation of unusual organic molecules, including highly ringstrained, sterically crowded, fluxional, antiaromatic and other interesting structures. The importance of this synthetic approach is that the azo linkage serves as a means of introducing the critical (usually last) bond in the complex target molecule. This article presents a cross-section of such elegant synthetic utilization of azoalkanes for fused-, bridged- and spiro-cyclization. Our coverage of the large body of literature has been directed by the complexity and novelty of the products. Azoalkanes are usually prepared via cycloaddition of azo dienophiles to appropriate substrates.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 30
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 19 (1980), S. 151-171 
    ISSN: 0570-0833
    Keywords: Electrophilicity ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The most widely known electrophilic agents are protic acids and compounds with an electronsextet partial structure. Recent research has aimed at the development of new electrophilic reagents, with greater reactivity on the one hand and higher selectivity on the other, which would largely obviate the addition of Lewis acids (Friedel-Crafts catalysts), and also allow control of the isomer ratio in reactions with ambivalent substrates. Compounds with “super-leaving groups”, such as trifluoromethanesulfonate and fluorosulfate, have been demonstrated as most advantageous in this respect since they are sufficiently polarized or dissociated for reactions to take place even in the absence of Friedel-Crafts catalysts. Heterocycles such as pyridones or imidazole are likewise suitable leaving groups; they are employed for their high selectivity, and also because they allow working under non-aqueous conditions.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 31
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 19 (1980), S. 276-289 
    ISSN: 0570-0833
    Keywords: Methylenecyclopropanes ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heterocyclic three-membered rings with an exocyclic double bond merit special interest in view of their ring strain and their fascinating chemistry. Their synthesis, thermal decomposition, ring opening, and cycloaddition reactions will be discussed in this review. α-Lactams, alkylideneaziridines, diaziridinones, and diaziridinimines belong to the best known classes, but the chemistry of alkylideneoxiranes and -thiiranes, α-lactones, α-thiolactones, thiiranimines, and aziridinimines has also been studied to some extent. Two elusive three-membered rings are oxiranimines and thiaziridinimines; the former were postulated as reactive intermediates in the thermal decomposition of α-lactams, whereas the latter were trapped efficiently with double and triple bonds during thermolysis of N-sulfonyliminothiatriazolines. In spite of many attempts to prepare thione derivatives of the title compounds, they are still unknown. Included in this review are also some open-chain dipolar species which are isomeric with the heterocyclic three-membered rings.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 32
    ISSN: 0570-0833
    Keywords: Quinones ; Quinones ; Michael addition ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: If catechol or other hydroquinones are dehydrogenated in the presence of a nucleophilic reagent, the latter reacts, usually by Michael addition, with the quinone formed in situ. The wide range of possible variations offered by this synthetic method is comprehensively described in the present paper. procedures are given for carrying out typical reactions.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 33
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 250-260 
    ISSN: 0570-0833
    Keywords: Unsaturated fatty acids ; Fatty acids ; Carbonyl olefination ; Synthetic methods ; Wittig reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that carbonyl olefination, i.e. the reaction of carbonyl compounds with alkylidene phosphoranes, can be sterically controlled. In some cases cis-olefins can be obtained by proper choice of the reaction conditions; trans-olefins are formed only in the presence of suitable structural factors. These cis-and trans-olefination reactions have opened new, stereo-specific routes to unsaturated and polyunsaturated fatty acids with differing positions and sequences of cis- and trans-double bonds and to ω-hydroxy and branched chain fatty acids.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 34
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 333-341 
    ISSN: 0570-0833
    Keywords: Strained molecules ; Heterocycles ; Diaziridines ; Diazirines ; Oxaziranes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Since their discovery five years ago, the diaziridines have become an extensive and easily accessible class of compounds. Hydrolysis of these compounds effects a simple synthesis of hydrazine, alkylhydrazines, and N,N′-dialkylhydrazines. They are also powerful oxidizing agents. The rigidity of the three-membered ring gives rise to a few stereoelectronic peculiarities. Investigations on the mechanism of formation of the three-membered rings led to a new synthesis of oxaziranes and to discovery of the isomeric oximes with a three-membered ring structure. The latter decompose readily to form diimide. Diazirines are cyclic isomers of the aliphatic diazo compounds and are surprisingly easy to obtain by dehydrogenation of suitable diaziridines; they are chemically much more stable than the linear isomers. Grignard reagents add onto the N=N double bond without destruction of the three-membered ring. Thermal decomposition yields carbenes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 35
    ISSN: 0570-0833
    Keywords: Cyclization ; Dialdehydes ; Nitromethane ; Carbohydrates ; Polyalcohols ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Condensation of nitromethane with suitable diadehydes in alkaline medium provides a general method of cyclization, in which the methyl group of the nitromethane is incorporated into the ring. This method leads to 5-, 6-, and 7-membered rings and is equally applicable to aliphatic, aromatic, and sugar dialdehydes. For example, glyoxal is converted into 1,4-dideoxy-1,4-dinitro-neo-inositol, and glutaraldehyde into trans-2-nitrocyclohexane-1,3-diol, while the corresponding cyclization of xylo-trihydroxyglutaraldehyde leads to deoxy-nitroinositols having the scyllo, myo-1, and muco-3 configurations.-In the case of aromatic dialdehydes, the cyclization is accompanied by elimination of water. Thus, phthalaldehyde, naphthalene-2,3-dicarboxaldehyde, and homophthalaldehyde yield, respectively, 2-nitroindenol, 2-nitrobenzindenol, and 2-nitronaphthalene. -Application of the method to sugar dialdehydes (aldehydic diglycol derivatives of monosaccharides formed by periodate oxidation) constitutes an excellent synthesis of 3-amino sugars, since 3-deoxy-3-nitropyranoses are formed smoothly on cyclization, and the corresponding 3-amino derivatives are obtained by hydrogenation. Thus, the reaction sequence: periodate oxidation → cyclization with nitromethane → hydrogenation, leads in the case of α-and β-D-pentosides to 3-amino-3-deoxy-D-and-L-pentosides, respectively, with ribo, xylo, and arabino configurations. α-D-hexosides give derivatives with gluco, manno, and galacto configurations. 3-Amino-3,6-dideoxyglucosides of the D-and L-series are obtained from 6-deoxy-D-or-L-hexosides, respectively, and 3-aminohexosans with gulo, ido, and altro configurations are obtained from 1,6-anhydro sugars. Cyclization of the dialdehydes obtained from sedoheptulose and methyl 4,6-O-ethylidene-α-D-glucoside by periodate oxidation, leads to 3-nitro and, after hydrogenation, to 3-amino derivatives of 3-deoxyheptopyranoses.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 36
    ISSN: 0570-0833
    Keywords: Kinetics ; Dipolar cycloaddition ; Cycloaddition ; Heterocycles ; Reaction mechanisms ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Criteria for the mechanism of 1,3-dipolar cycloadditions which lead to 5-membered rings are provided by the stereoselectivity observed with cis-trans isomeric dipolarophiles, by the effect of solvent and substituents on the rate constants, by the activation parameters, and by orientation phenomena. A concerted addition, which can also be described in terms of molecular orbitals and in which the two new σ-bonds are formed simultaneously, although not necessarily at equal rates, offers the best explanation of the experimental facts.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 37
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 24-29 
    ISSN: 0570-0833
    Keywords: 3-Aminoquinazol-4-one ; 3-Aminobenzotriazin-4-one ; Quinazolones ; Benzotriazinones ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Among the derivatives of 3-aminoquinazol-4-one and 3-aminobenzotriazin-4-one are compounds with narcotic, sedative, analgetic, and muscle-relaxant properties. Of special interest are compounds with one or several urethane groups and those substituted in the 3-position by a morpholine moiety.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 38
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 225-238 
    ISSN: 0570-0833
    Keywords: Pyridinium salts ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This review discusses syntheses leading to a new type of N-vinylpyridinium salts, to novel anionocyanines, to aminophenazines and alloxazines, as well as to (aza-) dehydroquinolizinium, acridizinium, and morphanthridizinium salts. In addition, Mannich reactions and aminoalkylations at active methylene groups of cycloimmonium salts, and their reactions with amines are treated. The possibilities offered by the “Ortoleva-King” reaction are demonstrated using numerous examples, such as a new route leading to the yohimbine skeleton.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 39
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 459-476 
    ISSN: 0570-0833
    Keywords: Aminoguanidine ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Due to its unique structure, aminoguanidine is capable of reacting as a derivative of hydrazine, guanidine or formamidine. Addition and condensation reactions yield products which can be cyclized to heterocyclic compounds. Frequently, heterocyclics are directly accessible from aminoguanidine in one stage.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 40
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 565-598 
    ISSN: 0570-0833
    Keywords: Dipolar cycloaddition ; Cycloaddition ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In contrast to the very large number of special methods applicable to syntheses in the heterocyclic series, relatively few general methods are available. The 1,3-dipolar addition offers a remarkably wide range of utility in the synthesis of five-membered heterocycles. Here the “1,3-dipole”, which can only be represented by zwitterionic octet resonance structures, combines in a cycloaddition with a multiple bond system - the “dipolarophile” - to form an uncharged five-membered ring. Although numerous individual examples of this reaction were known, some even back in the nineteenth century, fruitful development of this synthetic principle has been achieved only in recent years.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 41
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 309-323 
    ISSN: 0570-0833
    Keywords: s-Triazines ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation and properties of s-triazine are discussed. Nucleophilic reagents (even water) readily attack s-triazine. Thus, open-chain and heterocyclic compounds, e.g. formamidines, aminomethylene compounds, and triazole, pyridine, and pyrimidine deravatives are accessible from s-triazine. With amidines and imido ethers substituted triazines are obtained (by trans-triazination).The latter are formed via open-chain intermediates.
    Additional Material: 11 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 42
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 380-393 
    ISSN: 0570-0833
    Keywords: Pyridinium salts ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cleavage of N-phenylpyridinium or N-vinylpyridinium salts with secondary aliphatic amines leads to aromatic amino compounds or enamines which are often unobtainable by other routes. The other fragment, glutacondialdehyde or its monoanil, gives azulenes, as shown by Ziegler and Hafner, as well as König; these compounds can also be prepared from alkylpyridinium salts with cyclopentadienylsodium (Hafner). Syntheses of labile aldehydes which are otherwise difficult to obtain and of α-ketocarboxylic acids, starting from pyridinium salts and proceeding via nitrones or α-cyanoanils, are illustrated by many new examples. Benzimidazoles, benzothiazoles, and amidines are accessible from pyridinium salts via nitrones or α-cyanoanils; cyanoanils can be transformed into quinoxalines (including xanthopterine), perimidines, etc. Furthermore, nitrosonaphthols and nitrosonaphthylamines react with pyridinium salts containing an active methylene group on the nitrogen, leading to new ring systems. Further synthetic possibilities arise from nucleophilic displacements of the pyridine in pyridinium salts by SN 2 reactions. Combination of the route via nitrones with the methods of Arndt-Eistert, Ortoleva-King, or with chloromethylation constitutes a significant enlargement of its range of application. The formation of α-cyanoanils from diazoketones permits synthesis of α-keto-β-amino acids from α-amino acids, or of phenylglyoxylic acids from benzoic acids by chain extension.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 43
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 1 (1962), S. 8-21 
    ISSN: 0570-0833
    Keywords: Addition ; Immonium ions ; Isocyanides ; Amino acids ; Synthetic methods ; Alkylidene ammonium ions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The α-addition of immonium ions and anions (OH-, SeH-, S2O3 2-, N3- NCO- NCS-, R—CO2 -, RO—CO2-) to isonitriles, accompanied by secondary reactions provides a means for the one-stage synthesis of organic nitrogen compounds starting with two to five different components. Thus, by the condensations of amines (ammonia, primary, and secondary aliphatic and aromatic amines, hydrazines) and aldehydes or ketones with isonitriles and acids, a number of α-aminocarboxylic acid amides, thioamides, selenoamides, 1,5-disubstituted retrazoles, hydantoin imides, thiohydantoin imides, α-acylamino carboxylic acid amides, oligopeptide derivatives, β-lactams, derivatives of penicillanic acid, urethanes, diacylimides, and various hydrazine derivatives, can be prepared. The reactions are easily carried out and take place under mild conditions. Yields of more than 90% are frequently encountered.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 44
    ISSN: 0570-0833
    Keywords: Amides ; Azolides ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 45
    ISSN: 0570-0833
    Keywords: Michael addition ; Pyridinium salts ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By Michael addition of the active methylene groups in pyridinium salts onto suitable acceptor compounds, α-pyridones, substituted pyridines, particularly pyridinecarboxylic acids and pyridylpyridines, including the minor alkaloid of tobacco nicotelline and annelized pyridines, can be prepared by a simple procedure and generally in good yields. From the Michael adducts, polycyclic aromatic hydrocarbons, e.g. substituted fluoranthenes and “bisfluoranthenes” can be prepared; internal Michael addition leads to pyrrolinopyrdinium salts. For example, Michael addition of pyridinium salts onto quinones gives phenacyl substituted quinones, from which benzofurans and cinnolines can be readily obtained.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...