REDUCTION OF ACETYLENES BY CHROMIUM(II)-AMINE COMPLEXES

Alkylphenylacetylenes are reduced to the corresponding olefins by Cr(II)-amine complexes with a very high stereoselectivity for the cis isomer. Terminal acetylenes are likewise reduced, but dialkylacetylenes are not reactive to these reagents. The relative efficiencies of the Cr(II) complexes from several amines have been compared. Substituted propargyl alcohols are converted to allylic alcohols by the Cr(II) reagents, but in this instance mixtures of the cis and trans isomers are obtained. The product ratios depend on the nature of the substitution on the propargyl alcohol and on the particular amine used to prepare the reagent. © 1979, American Chemical Society. All rights reserved.