Optically Active Epoxy Diols by Titanium-Catalyzed Oxidation of Enantiomerically Enriched Hydroperoxy and Hydroxy Homoallylic Alcohols

Abstract

The Ti‐catalyzed epoxidation of optically active (S,S)‐hydroperoxy homoallylic alcohols 2 affords the epoxy diol (S,R,S)‐4 in high diastereoselectivity (d.r. up to 95:5), while the optically active hydroxy homoallylic alcohols (R,R)‐3 are epoxidized by the β‐hydroperoxy alcohol 5 under titanium catalysis to the corresponding epoxy (R,S,R)‐diol 4 in a diastereomeric ratio up to > 99:1. This high diastereoselectivity is rationalized in terms of a rigid template for the oxygen transfer, in which the hydroperoxy alcohol 2 or 5 is ligated tridentately and the diol 3 bound bidentately to the titanium metal. Through these oxidative routes, both enantiomeric epoxy diols 4 are conveniently accessible.

Horseradish Peroxidase-Catalyzed Enantioselective Reduction of Racemic Hydroperoxy Homoallylic Alcohols: A Novel Enzymatic Method for the Preparation of Optically Active, Unsaturated Diols and Hydroperoxy Alcohols

“…Important for synthetic applications is the fact that the present enzymecatalyzed resolution may be performed on the preparative scale to provide readily and convenienty optically active R,β-unsaturated (S,S) and (S,R) hydroxy-functionalized hydroperoxides 1, as well as (R,R) and (R,S) diols 2, for asymmetric transformations. Attractive applications constitute their Ti(OiPr) 4 -catalyzed oxidation to optically active epoxy diols 14 or the epoxidation of allylic alcohols by optically active hydroperoxides. 15 Experimental Section Materials and Methods.…”