Rhodium-catalyzed asymmetric addition of aryl- and alkenylboron reagents to electron-deficient olefins

Asymmetric 1,4-arylation and -alkenylation was achieved by use of organoboronic acids or their derivatives in the presence of a rhodium catalyst coordinated with binap or its related ligands. The scope of this asymmetric addition is very broad, alpha,beta-unsaturated ketones. esters, amides, 1-alkenylphosphonates, and 1-nitroalkenes being efficiently converted into the corresponding 1,4-addition products with over 95% enantioselectivity. The catalytic cycle in water is proposed to involve three intermediates [aryl- or alkenyl-rhodium (oxa-pi-allyl)rhodium, and hydroxo-rhodium] by NMR studies on the rhodium intermediates.