Intermolecular asymmetric Heck reactions with 2,2-diethyl-2,3-dihydrofuran

Palladium-catalysed intermolecular asymmetric Heck reactions were performed on 2,2-diethyl-2,3-dihydrofuran using chiral diphosphine and phosphinamine ligands. The steric effect of increased bulk at the 2-position was examine d for phenylations and cyclohexenylations and lower chemical yields, but si milar enantioselectivities were obtained compared to the 2,2-dimethyl analo gue. The optimum ee for phenylation was 94% and for cyclohexenylation was 9 3%, both obtained with the t-Bu-substituted diphenylphosphinoaryloxazoline ligand. (C) 2000 Elsevier Science Ltd. All rights reserved.