Sulphoxides, pyrolytic elimination

The configurations, conformations, chiroptic properties, and pyrolytic elimination reactions of steroidal sulphoxides and sulphinates, at C-3, C-6, and C-7, have been studied in detail. In general, though not without exception, the direction of elimination is controlled by the configuration at the sulphur atom, whenever two possibilities exist for the essential syn mechanism. The favoured... 

A two-step transformation of aldehydes into chloromethyl ketones entails reaction of the aldehyde with lithio chloromethylphenyl sulphoxide followed by pyrolytic elimination of phenylsulphinic acid (Scheme 82). ... 

Uses of Saturated Sulphides, Selenides, and Tellurldes in Synthesis.— These applications are mostly based on the C—C bond-forming reactions of sulphenyl carbanions the extensive uses of vinyl sulphides and their allyl and propargyl analogues are discussed in a later section. Some methods for C—S or C—Se bond cleavage, which are used to terminate a use in synthesis, have been discussed in an earlier section other methods, notably the conversion of the sulphide into a sulphoxide followed by pyrolytic elimination of the sulphenic acid, are covered in later sections. 

Reactions.—A variety of interesting and useful syntheses have been published involving the reaction of dimsyl anion [MeS(0)CHa ] with esters and lactones,with disulphides, with chlorosilanes, with sulphinate esters, with organoboranes, and with stilbenes. Simple and functionalized a-sulphinyl carbanions can be condensed with carbonyl compounds or alkylated, often in a stereocontrolled manner, as in a nicely conceived synthesis of biotin. Considerable attention has been given to methods for the removal of the sulphoxide function following carbon-carbon bond formation. Among the methods used are reduction by aluminium amalgam (with j3-keto-sulphoxides), reduction with Raney nickel, pyrolytic elimination of sulphenic acid, elimination of sulphur dioxide from sultines, e.g. (64), and sulphoxide-... 

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