Visible-Light-Activated Asymmetric β-C-H Functionalization of Acceptor-Substituted Ketones with 1,2-Dicarbonyl Compounds

We report a visible -light -activated asymmetric beta-C(sp(3))-H functionalization of 2-acyl imidazoles and 2-acylpyridines with 1,2-dicarbonyl compounds (typically alpha-ketoesters) catalyzed by a tailored stereo genic -at-rhodium Lewis acid catalyst. The C-C bond formation products are obtained in high yields (up to 99%) and with excellent stereoselectivities (up to >20:1 dr and up to >99% ee). Experimental and computational studies support a mechanism in which a photoactivated Rh-enolate transfers a single electron to the 1,2-dicarbonyl compound followed by proton transfer and a subsequent stereocontrolled radical-radical recombination.