NEW HOMOCHIRAL BIS(OXAZOLINE) LIGANDS FOR ASYMMETRIC CATALYSIS

Several homochiral bis(oxazolines), with asymmetric centers on the oxa zoline rings and on the side chains, were prepared from (1S,2S)-(+)-2- amino-1-phenyl-1,3-propanediol in high yields. Asymmetric cyclopropana tion of styrene with ethyl diazoacetate in the presence of 1 mol% of c opper(I) triflate and the dibenzoyl bis(oxazoline) 5a, gave ethyl 2-ph enylcyclopropanecarboxylate in up to 85% ee. The same ligand 5a, was u sed in the palladium catalysed enantioselective allylic substitution o f the 1,3-diphenyl-2-propenyl acetate to give the desired product in u p to 90% ee. (C) 1997 Elsevier Science Ltd.