Copper-Catalyzed [3+2] Cycloaddition Reactions of Isocyanoacetates with Phosphaalkynes to Prepare 1,3-Azaphospholes.

A novel copper-catalyzed synthetic method is described for phosphorous- and nitrogen-containing heterocycles such as 1,3-azaphospholes. Cycloaddition reactions of various isocyanoacetates with phosphaalkynes in the presence of copper bromide, bis(diphenylphosphino)methane (dppm), and potassium carbonate afford the corresponding 1,3-azaphospholes in high yields with complete selectivity. Some dppm-bridged dicopper complexes were identified as active species for the formation of 1,3-azaphospholes.