Enantioselective Total Synthesis of (+)-Propolisbenzofuran B†

Abstract

The first catalytic asymmetric total synthesis of (+)-propolisbenzofuran B, enabled by a highly enantioselective rhodium-catalyzed hydrogenation of a tetrasubstituted olefin, was described. Other noteworthy aspects include the construction of the central hydrodibenzo[b,d]furan core through a sequence of Zn(II)-mediated regioselective benzofuran formation and Dieckmann condensation, as well as C-H oxidations, involving a visible light-induced Fe(III)-catalyzed benzylic C(sp³)-H oxidation. Additionally, the absolute configuration was confirmed by X-ray analysis of a carbonate intermediate.