Intramolecular formal [4 + 2] cycloaddition of nitriles with amides triggered by TMSOTf/Et3N: highly efficient construction of pyrrolo[1,2-a]pyrimidin-4(6H)-ones.

By treatment with TMSOTf/Et3N, N-(2-cyanoarylmethyl)-substituted acrylamides or beta-ketoamides underwent N-addition cascades under mild conditions to afford the corresponding pyrrolo[1,2-a]pyrimidin-4(6H)-ones as the formal [4 + 2] cycloaddition products in high yields.