One-pot Two-Step Cycloaddition Reaction for Convenient Synthesis of Polycyclic Spirooxindole-fused [1,3]Oxazines

The novel spirooxindoline fused [1,3]oxazines were efficiently synthesized from Diels-Alder reaction of N-arylmaleimides with 1,2-dihydro-2-oxospiro[3H-indole-3,2'-[2H,9aH-pyrido[2,1-b][1,3] oxazines], which were generated in situ from three-component reactions of substituted pyridines and isatins with methyl propiolate, or dimethyl acetylenedicarboxylate. The stereochemistry of the products was clearly clarified by the analysis of H-1 NMR data and single crystal structures of the obtained polycyclic compounds.