Phosphine-catalyzed [3 + 2] cycloaddition of sulfamate-derived cyclic imines with allenoate: synthesis of sulfamate-fused dihydropyrroles.

Ph3P-catalyzed [3 + 2] cycloaddition reaction of sulfamate-derived cyclic imines with allenoate has been developed, affording sulfamate-fused dihydropyrroles under very mild conditions in high yields. Using amino acid-based bifunctional phosphine as chiral catalyst, its asymmetric variant provided the corresponding products in good yields with moderate to excellent enantiomeric excesses (up to 91% yield and up to 98% ee). Subsequent transformations of the heterocyclic products gave various pharmaceutically attractive compounds.