Rh-Catalyzed Enantioselective [4+2] Cyclization of 4-Alkynals and Acrylamides

Significance

A Rh-catalyzed intermolecular [4+2] cycloaddition of 4-alkynal and N,N-dialkyl­acrylamides afforded cyclohexanones in moderate to excellent yields and excellent ee’s. It was found that the cationic rhodium precursor and bidentate (R,R)-walphos ligand gave the optimal results in both yield and ee. A good range of substituents on the alkynal was compatible. In general, reactions with 2-alkynylbenzaldehydes are easier than those with linear alkynals, presumably due to the limited conformational options in the substrate.