New pinene-derived pyridines as bidentate chiral ligands

A synthesis of new bidentate pyridines 8a-d, 9, and 10 has been developed, starting from triflate 14, readily available from beta-pinene 11. A copper complex of the pyridine-oxazoline ligands 8a has been found to catalyze asymmetric allylic oxidation of cyclic olefins 36a-c with good conversion rates and acceptable enantioselectivity (<= 67% ee). The imidazolium salt 10 has been identified as a precursor of the corresponding N,N'-unsymmetrical N-heterocyclic carbene ligand, whose complex with palladium catalyzed the intramolecular amide enolate alpha-arylation leading to oxindole 45 in excellent yield but with low enantioselectivity. (c) 2008 Elsevier Ltd. All rights reserved.