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Eliminations from Olefins (1965)

Köbrich, G.

Weinheim : Wiley-Blackwell

Angewandte Chemie International Edition in English 4 (1965), S. 49-68

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ISSN: 0570-0833

Keywords: Elimination ; Alkenes ; Alkynes ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Eliminations from olefins are very often initiated by bases, and usually lead to formation of acetylene derivatives. In view of the numerous side-reactions and subsequent additions or rearrangments observed, the nature of the base used is of considerable significance. Organometallic bases are very versatile. In addition to dehydrohalogenation, dehalogenation by metals, and also thermolytic and photolytic eliminations. (e.g. the retrodiene reaction with exchange of substituents) are discussed. Elimination from low-membered cyclic olefins yields cycloalkynes having strained ring-systems, and the existence of these can be demonstrated by trapping them. The mechanisms known for β-elimination (E2, E1 and E1cB) occur also in the case of olefins; however - due to the sp2-hybridization of the carbon atoms taking part - they are realized with different rates of reaction relative to saturated compounds. α-Eliminations from olefines having aryl residues in the β-position lead to formation of arylacetylenes by rearrangement of the carbon skeleton. The mechanism of this reaction, which is known as the Fritsch-Buttenberg-Wiechell rearrangement, is discussed in considerable detail, and several variations of the reaction are considered. According to present-day knowledge carbenes are involved in α-eliminations only when both β-positions of the olefin are occupied by aliphatic substituents, or when they are occupied by aromatic residues where rearrangement to acetylenes is impossible for steric reasons (as for example with 9-chloromethylenefluorene). With organolithium compounds a number of dehydrohalogenations, which are formally β-eliminations, actually proceed via deprotonation on the halogenbearing carbon atom (α-metallation). α-Metallations are the rate-determining steps when ether is used as solvent, but proceed quickly in tetrahydrofuran even at low temperatures. Compounds of the type \documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$\raise1pt\hbox{$〉$}{\rm C}\raise1pt\hbox{=\kern-3.45pt=}{\rm C(Li)Cl}$\end{document} may be prepared by this method and are recognized as intermediates in α-eliminations.

Additional Material: 2 Tab.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/anie.196500491

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Chemistry and Stereochemistry of FluorophosphoranesPresented in part as lectures at Newark, Delaware (U.S.A.) (Feb. 23rd, 1963); Argonne, Illinois (U.S.A.) (Sept. 4th, 1963); Birmingham (England) (Dec. 13th, 1963); Cambridge (England) (Feb. 11th, 1964); Saarbrücken (Germany) (Feb. 18th, 1964); Glasgow (Scotland) (April 28th, 1964); Heidelberg (Germany) (May 22nd, 1964); Wien (Austria) (Sept. 9th, 1964). (1965)

Schmutzler, R.

Weinheim : Wiley-Blackwell

Angewandte Chemie International Edition in English 4 (1965), S. 496-508

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ISSN: 0570-0833

Keywords: Fluorophosphoranes ; Phosphoranes ; Stereochemistry ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Flurophosphoranes are a recently discovered new type of phosphorus compound derived from phosphorous pentafluoride by substitution of fluorine atoms with various groups. Synthesis, chemistry, and stereochemistry of this class of compounds containing phosphorus in the comparatively rare coordination number 5 will be discussed.

Additional Material: 12 Tab.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/anie.196504961

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New Reactions of Alkylidenephosphoranes and their Preparative Uses. Part I: The Acid-Base Character of Phosphonium Salts and AlkylidenephosphoranesParts II and III will appear shortly in this journal. (1965)

Bestmann, H. J.

Weinheim : Wiley-Blackwell

Angewandte Chemie International Edition in English 4 (1965), S. 583-587

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ISSN: 0570-0833

Keywords: Alkylidenephosphoranes ; Phosphonium salts ; Synthetic methods ; Phosphoranes ; Ylides ; Alkenes ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Phosphonium salts may be regarded as Bronsted acids, and alkylidenephosphoranes as the conjugate bases. Compounds of the two classes exist in equilibrium with each other. Phosphonium salts and alkylidenephosphoranes can be obtained by this “transylidation”. Other methods are also given for the preparation of members of both classes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/anie.196505831

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New Reactions of Alkylidenephosphoranes and their Preparative Uses. Part II. Alkylidenephosphoranes and Halogen CompoundsFor Part I see Angew. Chem. 77,609 (1965), Angew. Chem. internat. Edit. 4, 583 (1965). Part III will appear shortly in this journal. (1965)

Bestmann, H. J.

Weinheim : Wiley-Blackwell

Angewandte Chemie International Edition in English 4 (1965), S. 645-660

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ISSN: 0570-0833

Keywords: Alkylidenephosphoranes ; Phosphonium salts ; Synthetic methods ; Phosphoranes ; Ylides ; Alkenes ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The reaction of alkylidenephosphoranes with compounds containing halogens can be used to prepare ylides, which can be converted in to useful products, e.g. by hydrolysis, by thermal decomposition, or by other reactions. Examples of such products are ketones including cyclic, unsaturated, and branched-chain ketones (including cyclic, unsaturated, and branched-chain ketones), carboxlic esters (including those of unsaturated, branched- chain, polyenecarboxylic, acetylenecarboxylic, and allenecarboxylic acids), and aldehydes.

Additional Material: 10 Tab.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/anie.196506451

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New Reactions of Alkylidenephosphoranes and their Preparative Uses IIIFor Part I, see Angew. Chem. 77, 609 (1965) Angew. Chem. internat. Edit. 4, 583 (1965); for Part II, see Angew. Chem. 77, 651 (1965); Angew. Chem. internat. Edit. 4, 645 (1965).. Alkylidenephosphoranes and Reagents Containing Multiple Bonds (1965)

Bestmann, H. J.

Weinheim : Wiley-Blackwell

Angewandte Chemie International Edition in English 4 (1965), S. 830-838

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ISSN: 0570-0833

Keywords: Alkylidenephosphoranes ; Phosphonium salts ; Synthetic methods ; Phosphoranes ; Ylides ; Alkenes ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: A few examples of preparatively useful syntheses using alkylidenephosphoranes and substances containing a C—N or C—C double bond are the preparations of olefins, allenes, pyran derivatives, and cyclopropane derivatives. Olefins, ketones, and monocyclic compounds can be obtained by autoxidation of alkylidenephosphoranes; α, β-dioxo compounds (including cyclicones) can be prepared by oxidation with peroxy-acids. Alkylidenephosphoranes can also be used for the synthesis of azines and Schiff bases. Of the many possibilities offered by the Wittig reaction, only the preparation of tritiated aldehydes and olefins will be considered.

Additional Material: 1 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/anie.196508301

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Cyclic Compounds as Configurational Models for Stereoregular Polymers (1965)

Farina, M. ; Peraldo, M. ; Natta, G.

Weinheim : Wiley-Blackwell

Angewandte Chemie International Edition in English 4 (1965), S. 107-112

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ISSN: 0570-0833

Keywords: Configuration ; Polymers ; Tacticity ; Stereochemistry ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: It is possible to draw analogies between linear polymers and cyclic compounds. Stereochemical considerations developed in this connection led to the recognition of new aspects of importance for the systematic classification of both classes of compounds; for example, asymmetric structures can be predicted which had hitherto never been suspected. - The concept of “diasteric centers” is introduced, and the definition of an “asymmetric center” is expressed in more general terms.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/anie.196501071

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Recent Results of Configurational ResearchFrom a plenary lecture delivered at the general meeting of the Gesellschaft Deutscher Chemiker in Heidelberg (Germany), September 13th, 1963.Presentations of the entire field: K. Freudenberg: Stereochemie. Deuticke, Leipzig-Vienna 1933; W. Klyne: Progress in Stereo-chemistry. Wiley, New York 1954, Vol. 1, p. 177 ff.; E.L. Eliel: Stereochemistry of Carbon Compounds. McGraw-Hill, New York 1962. (1965)

Schlenk, W.

Weinheim : Wiley-Blackwell

Angewandte Chemie International Edition in English 4 (1965), S. 139-145

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ISSN: 0570-0833

Keywords: Configuration ; Stereochemistry ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The problems involved in configurational research differ from those of many of the currently important fields of general chemistry. Consequently, many chemists are less familiar with recent developements in this field than, for example, with those of the generally important modern ideas on valence and reaction mechanisms. A survey of new methods and recent results of configurational studies is attempted in this review, some unpublished experimental findings by the author being included. However, no attempt has been made to present an exhaustive review, nor to give a detailed treatment of individual problems which may interest the specialist.

Additional Material: 2 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/anie.196501391

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