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.
Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35043, Marburg, Germany.
Chuanyong
C
Wang
Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35043, Marburg, Germany.
Klaus
K
Harms
Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35043, Marburg, Germany. meggers@chemie.uni-marburg.de.
Eric
E
Meggers
C−H activation; asymmetric catalysis; photochemistry; radicals; rhodium