Stereoselective synthesis of 2-hydroxymorpholines and aminodiols via a three-component boro-Mannich reaction

The three-component coupling of an 1,2-aminoalcohol, a 1,2-dicarbonyl compound and a boronic acid was investigated. The reaction is supposed to proceed through the formation of a heterocyclic iminium species followed by the addition of the organoboron derivative. The diastereoselectivity of this process is discussed. Best results were observed when the probable intermediate was generated from a preformed 3-phenylthiomorpholin-2-ol. Products of this three-component boro-Mannich could be readily converted to the corresponding aminodiols by reduction with lithium aluminium hydride. (c) 2006 Elsevier Ltd. All rights reserved.