Catalytic Asymmetric Csp3 -H Functionalization under Photoredox Conditions by Radical Translocation and Stereocontrolled Alkene Addition.

This work demonstrates how photoredox-mediated C(sp3 )-H activation through radical translocation can be combined with asymmetric catalysis. Upon irradiation with visible light, α,β-unsaturated N-acylpyrazoles react with N-alkoxyphthalimides in the presence of a rhodium-based chiral Lewis acid catalyst and the photosensitizer fac-[Ir(ppy)3 ] to provide a C-C bond-formation product with high enantioselectivity (up to 97 % ee) and, where applicable, with some diastereoselectivity (3.0:1 d.r.). Mechanistically, the synthetic strategy exploits a radical translocation (1,5-hydrogen transfer) from an oxygen-centered to a carbon-centered radical with a subsequent stereocontrolled radical alkene addition.