Experimental and Theoretical Investigation of Asymmetric Induction in the Synthesis of Disubstituted Cyclohexadienes via Chiral Benzene Chromium Complexes

A series of [Cr(benzene)(CO)2L] complexes with L = PPh3, P(OMe)3, PPh2 ((?)-menthyl), P(OPh)2(O-(?)-menthyl), P(O-(?)-menthyl)3 were subjected to a nueleophile addition/acylation sequence to give trans-5,6-disubstituted cyelohexadienes. Low-to-moderate asymmetric induction was observed with the chira] ligands. Experimental and theoretical evidence for an alkylation at the metal center trans to the P ligand is presented, and a crystal structure determination of a [Cr(?5–cyclohexadienyl)(P(OMe)3)(CO)2SnPh3] complex is included.