Aryloxymethyltrifluoroborates for Rhodium-Catalyzed Asymmetric Conjugate Arylation. o-Methoxyarylation through 1,4-Rhodium Shift

Reaction of potassium aryloxymethyltrifluoroborates 1 with alpha,beta-unsaturated carbonyl compounds 2 in the presence of a chiral diene-rhodium catalyst in H2O at 100 degrees C introduced 2-methoxyaryl groups at the beta-position of 2 with high enantioselectivity in high yields. The reaction is assumed to proceed through 1,4-Rh shift from aryloxymethyl-Rh intermediate to 2-methoxyaryl-Rh. The high availability of phenol derivatives makes this asymmetric conjugate arylation synthetically useful.