Highly Enantioselective Copper−Bisoxazoline-Catalyzed Allylic Oxidation of Cyclic Olefins with tert-Butyl p-nitroperbenzoate
journal contributionposted on 29.06.2002, 00:00 by Merritt B. Andrus, Ziniu Zhou
Catalytic asymmetric allylic oxidation of cyclic olefins ocurrs for the first time in very high (94−99% ee) enantioselectivity using copper(I) complexes of malonyl derived bisoxazolines and tert-butyl p-nitroperbenzoate giving allyl benzoates in moderate yield. The copper complex, 15 mol %, was used in acetonitrile at −20 °C over an extended period, 5−12 d, with excess olefin together with one equivalent of perester. The S-esters were generated in accord with the model proposed previously for the (S,S)-bisoxazoline ligand. An η2 intermediate was ruled out using low-temperature 13C NMR with the complex in the presence of olefin.