Asymmetric Rh(I)-Catalyzed Functionalization of the 3-C( sp3)-H Bond of Benzofuranones with α-Diazoesters.

An asymmetric Rh(I)-catalyzed functionalization of the 3-C( sp3)-H bond of benzofuranones with α-diazoesters has been developed, providing a new strategy for the stereoselective 3-alkylation of benzofuranones. With low catalyst loadings (low to 0.02 mol % Rh), a number of benzofuranones bearing consecutive quaternary and tertiary stereogenic centers have been synthesized (up to 94% yield, 95:5 dr, and >99% ee). The synthetic utilities of this methodology have been demonstrated by elaborating the model product 3aa to a series of enantiopure compounds with similarities to natural products and drug candidates.