Deconjugative conversion of alpha-alkynyl esters to alpha,alpha-disubstituted beta-alkynyl esters.

We report the development of a method for the conversion of a variety of conjugated alpha-alkynyl esters to alpha,alpha-disubstituted beta-alkynylesters through the use of strong amide bases. Studies indicate that the second equivalent of base leads to the dianion intermediate. Optimal conditions included the use of 2 equiv of lithium diisopropylamide in THF with HMPA as the cosolvent followed by trapping with a variety of carbon electrophiles. Trapping with bis-electrophiles leads to spiro cycloalkane products.