Regioselective alkylation and olefination of allylic carbanion stabilized by two different heteroatoms: phosphorus and silicon

Treatment of allylphosphonate with LiHMDS, followed by successive addition of chlorotrimethylsilane and carbonyl reagent, afforded dienylsilanes in good yields. 3-Substituted dienylsilanes were obtained by alkylation and olefination of allylic carbanion of 3-trimethylsilylallylphosphonates.