Catalyst-free three-component sequencing for efficient assembly of [1,3] oxazine N-fused imidazole-2-thiones

A one-pot, catalyst-free, three-component sequential double-annulation from amine alcohols, glyoxal monohydrates and KSCN underwent imine formation/intramolecular cyclization/[3 + 2] cycloaddition. This tandem and green reaction offered [1,3] oxazine N-fused imidazole-2-thiones in a mild condition, with a very short reaction time, wide variation in functional groups, high efficacy on the gram-large scale and followed group-assisted purification chemistry work-up.