COPPER-CATALYZED REACTION OF TERMINAL ALKYNES WITH NITRONES - SELECTIVE SYNTHESIS OF 1-AZA-1-BUTEN-3-YNE AND 2-AZETIDINONE DERIVATIVES

Reaction of arylacetylenes with C,N-diarylnitrones using a catalyst sy stem of CuI-dppe (dppe = 1,2-bis(diphenylphosphino)ethane) in the pres ence of potassium carbonate in DMF predominantly affords the correspon ding 1,2,4-triaryl-1-aza- 1-buten-3-ynes in good yields. In contrast, the catalytic reaction using CuI in the presence of an excess amount o f pyridine as the ligand gives 1,3,4-triaryl-2-azetidinones as the maj or products. The reaction with aliphatic terminal alkynes in place of arylacetylenes produces the latter products irrespective of the cataly st system used. Asymmetric induction is also observed in the reaction of phenylacetylene with alpha,N-diphenylnitrone to give 1,2,4-tripheny l-2-azetidinone in the presence of chiral bisoxazoline-type ligands.