Enantioselective electrocatalytic oxidation of racemic sec-alcohols using a chiral 1-azaspiro[5.5]undecane-N-oxyl radical

Nitroxyl radical (6S,7R,10R)-4-acetylamino-2,2,7-trimethyl-10-isopropyl-1-a zaspiro[5.5]undecane-N-oxyl reveals a reversible redox peak in cyclic volta mmetry at + 0.62 V vs. Ag/AgCl. A preparative electrocatalytic oxidation of racemic sar-alcohols on the nitroxyl radical yielded mixtures of 51.4 - 63 .9 % ketones and 36.1 - 48.6 % alcohols by 10 h of electrolysis. The curren t efficiency and turnover number of the reactions were 85.6 - 87.9 % and 20 .6 - 25.6, respectively. The enantiopurity of the remaining (R)-isomers was 50 - 70 % and the S values as a selective factor was 4.1 - 4.6. (C) 1999 E lsevier Science Ltd. All rights reserved.