Tailored Aza‐Michael Addition as Key Step in the Synthesis of 1H‐imidazo[5,1‐c][1,4]oxazine Scaffolds

Abstract A novel protocol for the efficient synthesis of 1 H ‐imidazo[5,1‐ c ][1,4]oxazines has been developed. Aza‐Michael addition of selected primary amines to 1,2‐diaza‐1,3‐dienes (DDs) combined with isothiocyanates or isocyanates in sequential 3‐CR process, affords 2‐thiohydantoins and hydantoins with suitably positioned functional groups to be used for chemoselective acid‐promoted ring‐fused formation.