Highly enantio- and regioselective allylic alkylations catalyzed by chiral[bis(dihydrooxazole)]molybdenum complexes

A series of chiral C-2-symmetric bis[dihydrooxazoles] with a trans-1,2-diam inocyclohexane backbone was synthesized. In view of the promising results o btained by Trost et al with related bis[pyridine] ligands, we tested these new ligands in the enantioselective molybdenum-catalyzed allylic alkylation of 1- and 3-monosubstituted allylic substrates. Enantiomer excesses of up to 98% and branched/linear ratios of up to 11 : 1 were obtained with (E)-3- (alkyl)allyl carbonates. (E)-3-Phenoxyallyl acetate gave a branclied/linear ratio of > 20:1 and an ee of 98%. Crystal structures of the free ligand 7a and of its tricarbonylmolybdenum(0) complex 28 are reported.