N.V. Rostovskii, P.A. Sakharo, M.S. Novikov, A.F. Khlebnikov, G.L. Starova
“Cu(I)-NHC-Catalyzed (2+3)-Annulation of Tetramic Acids with 2H-Azirines: Stereoselective Synthesis of Functionalized Hexahydropyrrolo[3,4-b]pyrroles”
Org. Lett., 2015, 17, 4148-4151
DOI:10.1021/acs.orglett.5b01883
A stereoselective and high-yield synthesis of hexahydropyrrolo[3,4-b]pyrroles from tetramic acids and 2H-azirines under Cu(I)–NHC catalysis is developed. An unusual N–C2 azirine bond cleavage, initiated by a copper enolate, was rationalized in terms of a free radical reaction mechanism.