The mechanism of addition of silanediyls (silylenes) to dienes is of topical interest. From an ingenious series of studies of the addition of dimethylsilanediyl, :SiMe2, to substituted dienes, Gaspar and his co-workers deduced from product composi- tion, including the degree of stereospecificity, that the initial step is 1,2-addition to form a vinylsilacyclopropane which then rearranges to form products, as illustrated in Scheme 1 for hexa-2,4-dienes. 1.2 They ...
