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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 276 (1975), S. 201-204 
    ISSN: 1618-2650
    Keywords: Best. von Glykolaldehyd, Glycerinaldehyd, Hydroxyaldehyden ; Volumetrie ; Dimere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurden die Möglichkeiten für die titrimetrische Bestimmung von dimerem Glykolaldehyd (Fp: 94–96° C) und dl-Glycerinaldehyd (Fp: 138–141° C) untersucht. Die systematischen Fehler der auf Grund verschiedener funktioneller Gruppen durchführbaren Messungen sind von der Stabilität ihrer cyclischen Halbacetale sowie von den ihrer Depolymerisation folgenden weiteren Gleichgewichten bestimmt. Das aus dem dl-Glycerinaldehyd gebildete Halbacetal besitzt höhere Stabilität als dasjenige aus dem Glykolaldehyd. Mit der Hydrogensulfit-Methode werden 95–96%, mit der Hydroxylamin-Methode dagegen 98–99% vom wahren Wert gefunden. In Wasser gelöst zersetzt sich der Glykolaldehyd verhältnismäßig rasch, und das Gleichgewicht kann durch beide Aldehydreaktionen quantitativ gegen die Monomerenform verschoben werden. Unsere Untersuchungen ergaben, daß die Hydroxylamin-Methode zur Bestimmung der in Form cyclischer Halbacetale kristallisierenden, dimeren Hydroxyaldehyde Vorteile gegenüber der Hydrogensulfit-Methode bietet.
    Notes: Abstract Possibilities for the titrimetric determination of dimeric glycolaldehyde (m.p. 94–96° C) and dl-glyceraldehyde (m.p. 138–141° C) have been investigated. The systematic errors based on different functional groups depend on the stability of the cyclic semiacetals and on the subsequent equilibria established after their depolimerisation. The semiacetal of dl-glyceraldehyde is more stable than that of glycolaldehyde. 95–96% and 98–99% of the real content were found by the hydrogensulphite and hydroxylamine methods, respectively. Glycolaldehyde decomposes rather quickly in aqueous solution and the equilibrium can be shifted towards the monomeric form by both the aldehyde reactions. The hydroxylamine method proved to be more advantageous for the determination of the dimeric hydroxyaldehydes, which cristallise in the form of cyclic semiacetals.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,2,4-Oxadiazoles containing a C-5-heteroatom Bond, II Synthesis of 5,6-Dihydro-4H-1,2,4-Oxadiazines by ring Extention of Δ2-1,2,4-oxadiazolin-5-onesN-(2-Hydroxyalkyl)-, and N-(3-chloro-2-hydroxypropyl)-Δ2-1,2,4-oxadiazolin-5-one derivatives (6, 8), prepared by reaction of Δ2-1,2,4-oxadiazolin-5-ones (4) with alkylene oxides or epichlorohydrine, respectively, are used as starting materials for the synthesis of 5,6-dihydro-4H-1,2,4-oxadiazines (2) as well as for that of N-monosubstituted amidoximes (7, 11). The reactivity of 2 with methyl iodide and acylating agents is reported.
    Notes: Die durch Reaktion der Δ2-1,2,4-Oxadiazolin-5-one 4 mit Epoxiden bzw. Epichlorhydrin hergestellten N-(2-Hydroxyalkyl)- bzw. N-(3-Chlor-2-hydroxypropyl)-Derivate 6, 8 werden bei der Synthese von 5,6-Dihydro-4H-1,2,4-oxadiazinen (2) bzw. der N-monosubstituierten Amidoxime 7, 11 als Ausgangsmaterialien eingesetzt. Die Reaktionsfähigkeit von 2 gegenüber Methyljodid und Acylierungsmitteln wird beschrieben.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Investigation on the Chemistry of Berbans, IVSynthesis of Halogen Containing Depyrroloyohimbon Derivatives with PG-like and PG-antagonistic EffectHalogenation of depyrroloyohimbon derivatives of different configurations (1a-d, 2a-c, 3a-c) was investigated in order to obtain useful intermediates for the synthesis of depyrroloreserpines. The isomerisation of the primer products (9a-e, 10b and 11a, c, e) to γ-bromo derivatives (9f-j, 10g and 11f, h, j) was also studied.
    Notes: Die Halogenierung von Despyrroloyohimbon-Derivaten verschiedener Konfiguration (1a-d, 2a-c, 3a-c) wurde untersucht, um brauchbare Intermediärprodukte zur Synthese von Despyrroloreserpinen zu gewinnen. Die Isomerisierung von Primärprodukten (9a-e, 10b und 11a, c, e) zu γ-Brom-Derivaten (9f-j, 10g und 11f, h, j) wurde studiert.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 493-498 
    ISSN: 0009-2940
    Keywords: Pyrimido[6,1-a]isoquinolines / Pseudobases, heterocyclic / Ring-chain tautomerism ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In basis media, 4-substituted pyrimido[6,1-a]isoquinolin-2-imine hydrochlorides (4) constitute an equilibrium system involving the tautomeric forms characteristic of pseudobases 5, 6, 7 and the anhydro base 9. In aqueous solution in the pH range 7-13 the ammonium hydroxide form 5 is present. Between pH 13 and 14 the pseudobase 6 probably arises from this by covalent binding of the hydroxy group. 6 is then converted to the more stable imino type anhydrobase 9. Ring cleavage of 4 by excess alkali or of 9 by a small amount of water gives 1-(acylamidinomethylen)isoquinolines 7. Compounds 7 and 9 are stable in the solid state or in aprotic solutions but revert to cation 5 in dilute protic solutions.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 3183-3193 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of 4-Aminopyrimidines from 1,2,4-Oxadiazoles, I. A Novel General Method for the Preparation of 4-Aminoquinazolines and their Hetero AnaloguesCatalytic hydrogenation of 3-(2-aminoaryl)-1,2,4-oxadiazoles (9, 12, 15, 18, 21) to 2-amino-N-acylarenecarboxamidines (10, 13, 16, 19, 22) followed by dehydration gave condensed 4-aminopyrimidines (11, 14, 17, 20, 23), while the corresponding secondary amines (24) afforded 1,2-disubstituted 4-iminoquinazolines (26). Reduction and dehydration of 3-[2-(acylamino)phenyl]-1,2,4-oxadiazoles (28) provided, via a somewhat different pathway, 4-(acylamino)quinazolines (31).
    Notes: Katalytische Hydrierung von 3-(2-Aminoaryl)-1,2,4-oxadiazolen (9, 12, 15, 18, 21) zu 2-Amino-N-acylarencarboxamidinen (10, 13, 16, 19, 22) und nachfolgende Dehydratisierung ergab kondensierte 4-Aminopyrimidine (11, 14, 17, 20, 23), während die entsprechenden sekundären Amine (24) zu 1,2-disubstituierten 4-Iminochinazolinen (26) führten. Reduktion und Dehydratisierung der 3-[2-(Acylamino)phenyl]-1,2,4-oxadiazole 28 lieferte auf einem von dem vorangehenden teilweise verschiedenen Reaktionsweg die 4-(Acylamino)chinazoline 31.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Während die Reduktion von 5′-substituierten 1-[(1,2,4-Oxadiazol-3-yl)methyl]-3,4-dihydroisochinolinen (7) mit NaBH4 selektiv zu den entsprechenden Tetrahydroisochinolinen 8 und durch nachfolgende Ringisomerisierung zu Pyrazolo[5,1-a]isochinolinen 9 führte4), ergab die katalytische Hydrierung von 7 in Anwesenheit von Chlorwasserstoff durch reduktive Spaltung der N-O-Bindung des 1,2,4-Oxadiazolringes und nachfolgende spontane Dehydratisierung ganz allgemein 4-substituierte Pyrimido[6,1a]isochinolin-2-imin-hydrochloride (11).
    Notes: 5′-Substituted 1-[(1,2,4-oxadiazol-3-yl)methyl]-3,4-dihydroisoquinolines (7) were reduced by NaBH4selectively to give the corresponding tetrahydroisoquinolines (8) which underwent ring isomerization to pyrazolo[5,1-a]isoquinolines (9). Catalytic hydrogenation of 7 in the presence of hydrogen chloride, in turn, gave by reductive cleavage of the N-O bond of the 1,2,4-oxadiazole ring and subsequent dehydration, quite generally, 4-substituted pyrimido[6,1-a]isoquinolin-2-imine hydrochlorides (11).
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 1107-1112 
    ISSN: 0009-2940
    Keywords: ANRORC mechanism ; 1,2,4-Oxadiazoles ; 4(1H)-Quinazolone oximes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ringumwandlung von 1,2-disubstituierten 4(1H)-Chinazolonoximen zu 3,5-disubstituierten 1,2,4-OxadiazolenO-Benzoyl- und O-Acetyl-2-benzylaminobenzamidoxim (8b, c) ergeben in basischem Medium 5-substituierte 3-(2-benzylaminophenyl)-1,2,4-oxadiazole (9a, b), während Erhitzen in reinem Wasser zu 2-Amino-1-benzylbenzimidazol (10) führt. Reaktion von 2-(N-Acylbenzylamino)benzonitril (12) mit Hydroxylamin, oder Behandlung von O-Acyl-2-(N-benzoylbenzylamino)benzamidoxim (8f, g) with Säure ergibt die neuen 1,2-disubstituierten 4(1H)-Chinazolonoxime 13, die beim Erwärmen in Gegenwart von Alkali nach einem ANRORC-Mechanismus zu den 1,2,4-Oxadiazolen 9a, b isomerisieren.
    Notes: In basic media O-Benzoyl- and O-acetyl-2-benzylaminobenzamide oxime (8b, c) give 5-substituted 3-(2-benzylaminophenyl)-1,2,4-oxadiazoles (9a, b), while on heating in pure water 2-amino-1-benzylbenzimidazole (10) is formed. Reaction of 2-(N-acylbenzylamino)benzonitrile (12) with hydroxylamine, or treatment of O-acyl-2-(N-benzoylbenzylamino)benzamide oximes (8f, g) with acid give the novel 1,2-disubstituted 4(1H)-quinazolone oximes 13, which isomerize on heating with alkali by an ANRORC mechanism to the 1,2,4-oxadiazoles 9a, b.
    Additional Material: 1 Tab.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 111-113 
    ISSN: 0009-2940
    Keywords: Olefin formation ; Pyrimido[6,1-α]isoquinolines ; 4-Aminopyrimidines ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On heating at 100°C, 1,2,3,4-tetrahydro-6,7-dialkoxy-1-[(acylamidino)methylene]isoquinolines (5) are transformed into 4-substituted 6,7-dihydro-9,10-dialkoxy-2H-pyrimido[6,1-α]isoquinoline-2-imines (6), while at 140°C they undergo a novel prototropic rearrangement via 6 to give 4-amino-6-(4,5-dialkoxy-2-vinylphenyl)-2-phenylpyrimidines (7). The structure of 7a has been determined by X-ray analysis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 2065-2070 
    ISSN: 0009-2940
    Keywords: Ring-chain tautomerism ; 3H-[1,2,4]-Oxadiazolo[4,3-c]pyrimidine, 5,6,7,8-tetrahydro- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 3-aminopropionamide oxime (7) with two equiv. of benzaldehyde or of a substituted benzaldehyde gives cis-3,5-diaryl-5,6,7,8-tetrahydro-3H[1,2,4]oxadiazolo[4,3-c]-pyrimidines (cis-11a-c,e). According to 1H-, 13C-, and 15N-NMR studies these compounds form in solution a novel triple tautomeric equilibrium comprising cis- and trans-11a-c, e and 3-[2-(benzylidineamino)ethyl]-5-aryl-4,5-dihydro-1,2,4-oxaliazoles (10a-c, e). However, the solid obtained from 7 and two equiv. of cinnamaldehyde proved to be an imine (10g), which again formed in solution a similar triple tautomeric system analogously to the mutarotation of sugars. The structure of 11a and 10g was confirmed by X-ray crystallography.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0009-2940
    Keywords: 1,2,4-Oxadiazoles, 5-substituted, 3-(2-aminobenzyl)- ; Indoles, 2-(acylamino)- ; 8H-Pyrimido[1,6-a: 4,5-b']diindoles, 6-aryl ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Catalytic hydrogenation of 5-substituted 3-(2-aminobenzyl)-1,2,4-oxadiazoles 7 give 2-(acylamino)indoles 10. Treatment of 2-(benzoylamino)indoles 10a-c with acid leads to the novel 6-phenyl-8H-pyrimido[1,6-a: 4,5-b']diindoles 19a-c. A route for the new ring formation is proposed. Catalytic hydrogenation of 19a (Raney nickel, 70°C, atmospheric pressure) saturates the 6-phenyl ring but leaves the pentacyclic ring system intact. The structure of 19a is confirmed by an X-ray crystallographic analysis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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