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

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.