Addition Reactions of Heteroatom Nucleophiles onto Olefins with New Xantphos-Ru Complexes

摘要

Transition metal-catalyzed addition reaction of heteroatom nucleophiles onto olefins are one of the most powerful tools for functionalization of olefins, since the reaction proceeds with high level of atom economy and low loadings of transition metal catalysts. We have already reported that the ruthenium-catalyzed intermolecular addition reaction of carboxylic acids and alcohols onto olefins (Scheme 1). Wheareas these reports were the first reports about the transition metal-catalyzed addition of oxygen nucleophiles onto olefins, limited scope of the olefins substrates was problematic. To overcome the problem, we tested easily identified and tunable Ru(II) complexes as catalyst precursors. Our preliminary examinations proved that the Ru(II) catalysis ([(p-cymene) RuCl2]/AgOTf/diphosphine) showed good catalytic activity for the addition of carboxylic acids, alcohols, and sulfonamides onto styrene as well as Ru(III) catalyses reported previously. Of note is that xantphos was found to be the most suitable ligand for the addition reaction of the carboxylic acids onto the various inactive olefins among the ligands we tested. These results prompted us to develop new xantphos-Ru(II) complexes. Here, we will describe the preparation of new xantphos-Ru(II) complexes and application of these complexes to the addition reactions of heteroatom nucleophiles onto olefins.