First catalytic reductive coupling of 1,3-diynes to carbonyl partners: a new regio- and enantioselective C-C bond forming hydrogenation.

Upon exposure of diynes and glyoxals to cationic Rh(I) catalysts under 1 atm of hydrogen gas, regioselective condensation occurs to afford highly unsaturated enyne products without over-reduction. In the presence of chiral phosphine ligands, reductive coupling products are obtained in high enantiomeric excess at ambient temperature and pressure. The present studies are among the first examples of the electrophilic trapping of organometallic intermediates obtained transiently under the conditions of catalytic hydrogenation.