Intramolecular Cyclization of β-Alkynylpropanamides to γ-Alkylidene-γ-butyrolactams

Abstract A general method for the base-catalized intramolecular cyclization of β-alkynylpropanamides 1 to γ-alkylidene-γ-butyrolactames 2 (and 3 ) was established. Reactions of β-alkynylamides 1c-h , possessing alkyl groups at the terminal acetylenes, in the presence of a catalytic amount of LiN(TMS) 2 / AgOTf (= 2:1) in toluene gave exclusively ( Z )-alkylidenelactames 2c-h in good yields.