Stereoselective and Regioselective Thermal and Photochemical Preparation of Siloxy Dienes

Article abstract of DOI:10.1021/jo00367a015

It is shown that (Z)-2-hydroxy 2,4-dienes (Z-dienols), formed by photoenolization of the β-alkyl-α, β-unsaturated ketones 1a-e, can be trapped by a silylating reagent to give the (Z)-2-trimethylsiloxy 2,4-dienes 2a-e.This corresponds to stereoselective and regioselective production of just one of the three isomeric silyl dienol ethers which can be formed from each of these ketones.In contrast, silylation of the same ketones under thermal conditions generally gives the 2-trimethylsiloxy 1,3-dienes 4.Uniquely among the siloxy dienes examined, 3d apparently undergoes a rearrangement to 4d via a 1,5-hydrogen shift.