Deconjugative Conversion of α-Alkynyl Esters to α,α-Disubstituted β-Alkynyl Esters

摘要

We report the development of a method for the conversion of a variety of conjugated α-alkynyl esters to α,α-disubsti-tuted β-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.