Preparation of silyl-protected γ-hydroxylated α,β-unsaturated acetylenic ketones and their reactions with some nucleophiles

The t-butyldiphenylsiloxy derivatives were stable, whereas the trimethylsilyl analogs were unstable. The former compounds were reacted with diethylamine, lithium dimethylcuprate, and 1,3-propanedithiol and gave Michael adducts in good to very good yields.

The amine and cuprate gave the conjugated alkenones, the former in a stereospecific manner ( Z ), the latter stereospecifically ( E ) in one case but otherwise stereoselectively with an E preponderance. With the dithiol bisaddition occurred, and the corresponding 1,3-dithiane was obtained in excellent yield. Attempts to make 1,3-dithianes from 1,3-propanedithiol and 1,1-diethoxy-4-diethylaminoalk-3-en-2-ones failed.