Allylic silanes protodesilylation

Allylic or propargylic metal compounds are often intermediates in isomerization reactions of unsaturated systems (see Section 4.5.5) the product distribution on protonation depends very much on the substitution and the conditions of hydrolysis and most often mixtures of isomers are obtained. In contrast double bond shift generally occurs on protodesilylation of allylic silanes by acids, a reaction which takes place stereospecifically anti. Only when intramolecular delivery of the proton in a chair-like transition state is possible may a different kind of stereoselectivity be effective and good 1,3- or 1,4-induction in hydrogen transfer be observed (Scheme 83). ° ... 

Recently we investigated a new class of silyltriflates and we found that allyl substituted alkynyl-silanes react with triflic acid under protodesilylation of the allyl group. The resulting alkynylsilyl-triflates are interesting starting materials for chain-like oligomeric silylalkynes with various substituents (Eqs.(7,8)). 

For sulfoxides with P-silyl substituents there is some preference for elimination to take place towards the silyl group. On protodesilylation both the allyl- and vinyl-silanes formed give the same alkene, so providing a regioselective and high yielding alkene synthesis (Scheme 5). If there is no P-hydrogen,... 

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