[4+2]-Cycloaddition of para-Quinone Methides with Hexahydro-1,3,5-Triazines: Access to 1,3-Benzoxazine Derivatives

A [4+2]-cycloaddition of para-quinone methides with hexahydro-1,3,5-triazines is reported. The reaction occurs under very mild conditions (catalyst-, ligand-, and base-free), exhibits a broad substrate scope and excellent functional group tolerance, and affords a series of biologically important 1,3-benzoxazine derivatives in good to excellent yields. Moreover, the successful late-stage functionalization of pharmaceutically relevant compounds further renders the approach valuable.