Strained silacycles in organic synthesis: the tandem aldol-allylation reaction.

Allyl(crotyl)enolsilanes, when constrained in a five-membered ring with a 1,2-diol, react with aldehydes in a tandem aldol-allylation reaction to give polyketide fragments. These experimentally trivial and efficient reactions establish two new carbon-carbon bonds and up to four new stereocenters. The silane reagents, which owe their reactivity to strain release Lewis acidity, are easily prepared and stable to storage.