Regioselective hydrophenylation of olefins catalyzed by an Ir(III) complex

The novel, anti-Markovnikov, arylation of olefins with benzene to produce straight-chain alkylbenzenes with higher selectivity than branched alkylbenzenes is catalyzed by [Ir(mu-acac-O,O',C(3))(acac-O,O')(acac-C(3))](2) (acac = acetylacetonato), 1[J. Am. Chem. Soc. 122 (2000) 7414]. The reaction of benzene with propylene gave n-propylbenzene and cumene in 61 and 39% selectivities, respectively. The reaction of benzene and styrene afforded 1,2-diphenylethane in 98% selectivity. Considering the anti-Markovnikov regioselectivity and lack of inhibition by water, we propose that the reaction does not proceed via a Friedel-Crafts, carbocation, mechanism. Complex 1, amongst the various transition metal complexes examined, is the most efficient for catalyzing the anti-Markovnikov olefin arylation. The crystal structure of complex 1was solved and is consistent with a binuclear Ir(III) structure with three different types of coordinated acac ligands as reported by earlier solution IR and NMR analyses. [Ir(mu-acac-O,O',C(3))(acac-0,0')Cl](2), 2, was prepared by the reaction of complex 1 with benzoyl chloride, and the crystal structure was also reported. (C) 2002 Elsevier Science B.V. All rights reserved.