NbCl-Mg Reagent System in Regio- and Stereoselective Synthesis of (2)-Alkenylamines and (3)-Alkenylols from Substituted 2-Alkynylamines and 3-Alkynylols.

The reduction of ,-disubstituted 2-alkynylamines and substituted 3-alkynylols using the NbCl-Mg reagent system affords the corresponding dideuterated (2)-alkenylamine and (3)-alkenylol derivatives in high yields in a regio- and stereoselective manner through the deuterolysis (or hydrolysis). The reaction of substituted propargylamines and homopropargylic alcohols with the in situ generated low-valent niobium complex (based on the reaction of NbCl with magnesium metal) is an efficient tool for the synthesis of allylamines and homoallylic alcohols bearing a 1,2-disubstituted double bond. It was found that the well-known approach for the reduction of alkynes based on the use of the TaCl-Mg reagent system does not work for 2-alkynylamines and 3-alkynylols. Thus, this article reveals a difference in the behavior of two reagent systems-NbCl-Mg and TaCl-Mg, in relation to oxygen- and nitrogen-containing alkynes. A regio- and stereoselective method was developed for the synthesis of nitrogen-containing -β-chlorovinyl sulfides based on the reaction of 2-alkynylamines with three equivalents of methanesulfonyl chloride in the presence of stoichiometric amounts of niobium(V) chloride and magnesium metal in toluene.