Phosphane-Catalyzed [3+2] Cycloaddition Reaction of Allenoate and Cyclic Imines: A Simple and Efficient Method for Synthesis of Benzo-Fused Cyclic Sulfamidate Heterocycles

By using a phosphane as an organocatalyst, an efficient synthesis of benzo-fused cyclic sulfamidate heterocycles has been developed through a cycloaddition reaction of allenoate and cyclic imines including cyclic trifluoromethyl ketimine, which gave high yields (71-97%). The reaction could also be conveniently performed on a gram scale. Furthermore, some simple transformations of the sulfamidate heterocycle products have been disclosed to obtain functional amines. An asymmetric variant of this reaction was also tried by screening several commercially available chiral phosphane ligands as organocatalysts, and up to 36% ee was achieved.