in diethyl ether under Ar; O2 bubbled through soln. of Cu complex in Et2O at -80°Cfor 10 s; excess O2 removed; HCl in Et2O added at -80°C; stirred for 30 min; warmed to room temp.; distd. H2O added; stirred at room temp. for 1 h; Et2O layer washed with pentane; ppt. recrystd. from THF-pentane; vac. dried; elem. anal.;