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 analogues 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.