A Convenient Procedure for the Alkylation of Acetylenes

Abstract

Internal acetylenes are traditionally prepared by the alkylation of terminal acetylenes in liquid ammonia using sodium amide as the base.¹ Although the yields of internal acetylenes prepared in this manner are sometimes good, they are usually in the range of 30–60%. Normant has previously pointed out the efficacy of hexamethylphosphoramide (HMPA) as a solvent for alkylations of sodium acetylide.² In connection with other synthetic work, we have worked out a facile procedure which allows the synthesis of certain internal acetylenes in high yield. A typical experimental procedure follows