Rh(I)-Catalyzed Regio-\nand Enantioselective Ring Opening\nof Vinyl Cyclopropanes

We describe a Rh(I) catalyzed asymmetric ring opening\nof <i>racemic</i> vinyl cyclopropanes using aryl boronic\nacids as\nC-nucleophiles. When ferrocene-based chiral bisphosphines are used\nas ligands, the products are obtained with regioselectivities typically\n99:1 r.r. and ee’s generally between 88 and 96%. A wide range\nof aryl boronic acids can be used, and the products can be converted\ninto a variety of targets. Preliminary mechanistic studies indicate\nthat Zn(OTf)<sub>2</sub> plays a significant role in the reaction\nby promoting rhodium-ligand complex formation and accelerating the\nreaction. We expect this method and these mechanistic insights to\nbe useful in the development of new asymmetric methods.