Extremely efficient cross-coupling of benzylic halides with aryltitanium tris(isopropoxide) catalyzed by low loadings of a simple palladium(II) acctate/Tris(p-tolyl)phosphine system

Abstract

Highly efficient coupling reactions of benzylic bromides or chlorides with aryltitanium tris(isopropoxide) [ArTi(O-i-Pr)3] catalyzed by a simple palladium(II) Acctate/tris(p-tolyl)phosphine [Pd(OAc)2/ P(p-tolyl)3] system are reported. The coupling reactions proceed in general at room temperature employing low catalyst loadings of 0.02 to 0.2 mol%, affording coupling products in excellent yields of up to 99%. For benzylic bromides bearing strong electronwithdrawing cyano (CN) or trifluoromethyl (CF 3) substituents, the reactions require a higher catalyst loading of 1 mol%, or the reactions are carried out at 60°C. The catalytic system also tolerates (1-bromoethyl)benzene bearing β-hydrogen atoms while using a catalyst loading of 1 mol% to afford the coupling product in a 70% yield. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.