Preparation of chiral tricarbonyl arene thiol chromium and its application to asymmetric ring opening of meso-epoxides

Abstract

Optically active (R,S)- and (S,R)-tricarbonyl {2-[1-(N,N-dimethylamino)ethyl]benzenethiol}chromiums have been prepared in moderate yield by the regioselective lithiation of tricarbonyl [N,N-dimethyl-α(R)-phenylethylamine]chromium and subsequent reaction of the product with elemental sulfur. The structure of the (R,S)-benzenethiolchromium complex was fully characterized by X-ray crystallography. The chiral benzenethiolchromium complexes reacted with cyclopentene oxide, cyclohexene oxide, 1-methylcyclohexene oxide, cycloheptene oxide and cyclooctene oxide and, after oxidative removal of the chromium moiety, gave the corresponding trans β-hydroxyalkyl aryl sulfides in high yield with moderate diastereoselectivity. The reaction proceeded without additives and the diastereoselectivity was not affected by the addition of lanthanide(III) complexes which are known to promote the ring-opening of an epoxide with benzenethiol.