Chemoselective synthesis of 5,4'-imidazolinyl spirobarbiturates via NBS-promoted cyclization of unsaturated barbiturates and amidines.

A selective cyclization of unsaturated barbiturates and amidines promoted by N-bromosuccinimide has been successfully developed to afford a vast variety of 5,4'-imidazolinyl spirobarbiturates in moderate to good yields. The present protocol features broad substrate scope, facile work-up procedure and mild reaction conditions, providing a novel strategy for the highly selective and efficient construction of structurally diverse spiroimidazolines.