Oxidative Fragmentations of 2-(Trimethylsilyl)ethyl Sulfoxides − Routes to Alkane-, Arene-, and Highly Substituted 1-Alkenesulfinyl Chlorides

Abstract

The preparation of a collection of alkyl, aryl, and 1-alkenyl 2-(trimethylsilyl)ethyl sulfoxides is outlined, using mostly vinyltrimethylsilane or 2-(trimethylsilyl)ethanesulfenyl chloride (5) as key starting materials. The 2-(trimethylsilyl)ethyl group can be cleaved from many of the sulfoxides under oxidative fragmentation conditions using sulfuryl chloride and the reaction represents a new protocol for sulfinyl chloride synthesis. The method is suitable for most alkane- and arenesulfinyl chlorides (3), but is limited to highly substituted vinylic sulfinyl chlorides. 1-Alkenyl 2-(trimethylsilyl)ethyl sulfoxides with reduced double bond substitution (6, 7, 11) succumb to reactions involving chlorination of the double bond. The β-effect of silicon is invoked to explain the ability of the 2-(trimethylsilyl)ethyl group to induce C−S bond scission under the oxidative cleavage reaction conditions. A mechanism is offered to account for the role played by the β-silicon atom of the 2-(trimethylsilyl)ethyl group. Indeed, the silicon atom is self-sacrificial in that it diverts the course of the reaction from the usual α-carbon chlorination mode to one of oxidative cleavage, whereby the 2-(trimethylsilyl)ethyl group is lost. The overall reaction calls upon the ability of silicon atoms to donate electron density by hyperconjugation.