Enantioselective Addition of Terminal Alkynes to Aldehydes Catalyzed by a Copper(I)-TRAP Complex

摘要

Because of the versatility of the resulting propargylic alcohols, the addition of terminal alkynes to aldehydes serves as an important carbon-carbon bond formation reaction in the synthesis of complex molecules. Given the recent demand for highly efficient and environmentally friendly processes, the direct alkynylation of aldehydes that avoids the use of a stoichiometric amount of a reagent has become highly desirable. While recent efforts on this subject have led to the discovery of various catalytic reactions that involve metal species, reactions that feature the catalysis of Cu, to the best of our knowledge, has yet to be reported. Although Cu is the first transition metal element that was shown to promote carbonyl alkynylations, the catalytic use of a Cu species was hampered by the low reactivity of Cu(I) acetylides. Herein, we report the direct addition of terminal alkynes to aromatic aldehydes under mild conditions catalyzed by a Cu-phosphine complex, which was prepared in situ from Cu(O-t-Bu) and Ph-TRAP, to produce enantiomerically enriched propargyl alcohols with moderate enantioselectivities.