General and Synthetic Methods: Volume 6 (Specialist Periodical Reports, Band 6) - Hardcover

Hardcover

ISBN 10: 0851868746 ISBN 13: 9780851868745

Verlag: Royal Society of Chemistry, 1983

Inhaltsangabe

Specialist Periodical Reports provide systematic and detailed review coverage of progress in the major areas of chemical research. Written by experts in their specialist fields the series creates a unique service for the active research chemist, supplying regular critical in-depth accounts of progress in particular areas of chemistry. For over 80 years the Royal Society of Chemistry and its predecessor, the Chemical Society, have been publishing reports charting developments in chemistry, which originally took the form of Annual Reports. However, by 1967 the whole spectrum of chemistry could no longer be contained within one volume and the series Specialist Periodical Reports was born. The Annual Reports themselves still existed but were divided into two, and subsequently three, volumes covering Inorganic, Organic and Physical Chemistry. For more general coverage of the highlights in chemistry they remain a 'must'. Since that time the SPR series has altered according to the fluctuating degree of activity in various fields of chemistry. Some titles have remained unchanged, while others have altered their emphasis along with their titles; some have been combined under a new name whereas others have had to be discontinued. The current list of Specialist Periodical Reports can be seen on the inside flap of this volume.

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A series of reviews by leading specialists in their fields which gives systematic and comprehensive coverage of the progress in major areas of research.

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General and Synthetic Methods Volume 6

A Review of the Literature Published During 1981

By G. Pattenden

The Royal Society of Chemistry

Copyright © 1983 The Royal Society of Chemistry
All rights reserved.

ISBN: 978-0-85186-874-5

Contents

Chapter 1 Saturated and Unsaturated Hydrocarbons By J. M. Clough, 1, 
Chapter 2 Aldehydes and Ketones By S. C. Eyley, 56, 
Chapter 3 Carboxylic Acids and Derivatives By P. R. Jenkins, 98, 
Chapter 4 Alcohols, Halogeno-compounds, and Ethers By R. C. F. Jones, 154, 
Chapter 5 Amines, Nitriles, and Other Nitrogen-containing Functional Groups By G. Kneen, 193, 
Chapter 6 Organometallics in Synthesis, 218, 
Chapter 7 Saturated Carbocyclic Ring Synthesis By D. W. Knight, 277, 
Chapter 8 Saturated Heterocyclic Ring Synthesis By R. C. Brown, 312, 
Chapter 9 Highlights in Total Synthesis of Natural Products By A. P. Johnson, 371, 
Author Index, 395, 

CHAPTER 1

Saturated and Unsaturated Hydrocarbons

BY J. M. CLOUGH

1 Saturated Hydrocarbons

Several new and improved methods for the reductive removal of functional groups have been presented during the year. Extending a process developed for the reduction of secondary alcohols, Barton and his co-workers have shown that primary akohols, derivatized as xanthate or thiobenzoate esters, or as thiocarbonyl imidazolides, are deoxygenated without competing Chugaev elimination on treatment with tri-n-butyltin hydride at 130–150 °C. Selective derivatization of primary hydroxyl groups is straightforward, enabling them to be removed without affecting secondary hydroxyl or other functional groups. Primary and secondary alcohols, or their methyl or trimethylsilyl ethers, are conveniently deoxygenated via the corresponding iodides generated in situ by successive treatment with sodium iodide, chlorotrimethylsilane, and zinc. Diaryl- or triarylmethanols are reduced to the corresponding arylmethanes on refluxing with iron pentacarbonyl and benzoyl chloride in mesitylene.

A mixture of sodium borohydride and palladium chloride reduces aryl ketones and benzyl alcohols to the corresponding hydrocarbons. Carboxylic acid esters and non-activated hydroxyl groups are not affected by this new reducing system, but ketones are reduced to alcohols, and aromatic chlorine atoms are removed. Bis(benzoyloxy)borane, prepared in situ from BH3·THF and benzoic acid, is a convenient alternative to catecholborane for the reduction of the tosylhydrazone derivatives of aldehydes and ketones to hydrocarbons under mild conditions. Ketones that are relatively unhindered can be deoxygenated in the gas phase at 190 °C in the presence of hydrogen over a nickel–alumina catalyst. The main drawback of the method is the lack of selectivity: other functional groups are also lost under the reaction conditions. A mixture of sodium borohydride and cerium trichloride in methanol at room temperature fully reduces the carbonyl group of thiochromones to give the corresponding thiochromenes (Scheme 1). Chromones or their thiones remain unchanged under these reaction conditions.

Non-activated primary, secondary, or tertiary alkyl fluorides (as well as chlorides) are reduced in high yield to hydrocarbons by a solution of potassium and dicyclohexyl-18-crown-6 in diglyme or toluene at ambient temperature. Organotin hydrides can be supported on inorganic carriers like alumina or silica, enabling alkyl halides to be reduced under heterogeneous conditions. As an alternative to its use in dipolar aprotic solvents, sodium borohydride can be used to reduce alkyl chlorides, bromides, and iodides as well as sulphonate esters to alkanes under phase-transfer conditions. Dichloromethane solutions of the readily-available reagents P2I4 and PI3 reductively remove the halogen from α- iodo- and α-bromo-ketones, usually at room temperature and in high yield.

The research groups of Tanner and Ono have independently reported that tertiary and some secondary nitro groups are removed by reduction with tri-n-butyltin hydride in the presence of a radical initiator. Keto, ester, cyano, phenylthio, and primary nitro groups remain unchanged under the reaction conditions.

The sulphonyl group of α nitrosulphones is replaced by hydrogen on treatment with N-benzyl-1,4-dihydronicotinamide (BNAH) in deoxygenated DMF (Scheme 2). Keto and cyano groups are not affected. In the presence of a catalytic amount of azobis(isobutyronitrile), or under irradiation, BNAH also reduces alkylmercury(II) acetates to alkanes.

Olah and his co-workers have discovered that the reducing ability of magnesium in methanol is dramatically enhanced by the addition of a catalytic amount of palladium metal on carbon; even non-activated multiple carbon–carbon bonds are rapidly and completely reduced under these reaction conditions.

Following their recent disclosure of a three-step process for the replacement of oxygen in ketones by two methyl groups, Reetz and his co-workers have now shown that the transformation can be accomplished directly by treatment of the ketone with dimethyltitanium dichloride. Smooth geminal methylation occurs even when the product has two neighbouring quaternary carbon atoms, e.g. the terpene 'cuparene' (1). Methyltitanium chlorides (prepared from dimethylzinc and titanium tetrachloride in suitable proportions), or dimethylzinc and catalytic quantities of titanium tetrachloride, also methylate t-alcohols, t-ethers, t(reported in 1980) and s- (but not primary-) alkyl chlorides, and gem-dihalides (e.g. Scheme 3).

Metzger et al. have examined the addition of alkanes to a representative selection of activated, non-activated, and de-activated olefins at high temperature (650 — 723 K) and under high pressure (ca. 200 bar). Yields are strongly dependent on the reaction conditions and the olefin: alkane ratio, but regioselectivity, which seems to be controlled mainly by steric rather than electronic factors, is remarkably high in some cases, e.g. Scheme 4.

The free radicals generated by treating t-butyl, allyl, or benzyl halides with three equivalents of chromous chloride couple to form symmetrical dimers. Alternatively, a careful choice of reaction conditions enables good yields of cross-coupled products to be prepared, e.g. (2)->(3).

Benzyl chlorides and bromides undergo reductive coupling at room temperature and under neutral conditions on treatment with a small excess of chlorotris(triphenylphosphine)cobalt(I), e.g. (4) -> (5). Benzal bromide gives E-stilbene under the same conditions. Alternatively, benzyl, alkyl, and aryl chlorides, bromides, and iodides can be reductively coupled by using lithium in tetrahydrofuran under the influence of ultrasound. Little or no reaction occurs in the absence of sonic waves. Long straight-chain iodoalkanes (e.g. 1-iodotetradecane) undergo reductive coupling to give n-alkanes on treatment with hydrazine and a catalytic amount of palladium, but yields fall dramatically with shorter substrates.

Larock and Leach have described the first general method for the alkylation of a wide variety of organomercurials. For example, primary alkylmercurials cross-couple with alkylcuprates to give moderate yields of alkanes, e.g. (6)->(7); reactions involving secondary alkylmercurials are less efficient. [1,3-Bis(diphenylphosphino) propane] nickel(II) chloride catalyses the cross-coupling of alkylmagnesium halides or alkylalanes with arylphosphates to furnish...

Details zur Ausgabe

• Verlag: Royal Society of Chemistry
• Erscheinungsdatum: 1983
• Sprache: Englisch
• ISBN 10: 0851868746
• ISBN 13: 9780851868745
• Einband: Gebundene Ausgabe
• Anzahl der Seiten: 432
• Herausgeber: Pattenden G.
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: GPSR Kontakt; gpsr@libri.de; ; Friedensallee 273; Hamburg; 22763; Deutschland