Enhanced Efficiency of Amide-Substituted Quinuclidine-Boranes as Hydridic Hydrogen Atom Transfer Catalysts for Photoinduced Hydroalkylation of Unactivated Olefins†

An amide-substituted quinuclidine-borane has been identified as a more efficient hydridic hydrogen atom transfer (HAT) catalyst for the hydroalkylation of unactivated olefins under visible-light irradiation. ¹H NMR titration experiments reveal that the amide moiety of the quinuclidine-borane catalyst forms stronger hydrogen bonds with the carbonyl substrates, thereby improving the reaction yields. Furthermore, it was found that the reaction yields correlate well with the association constant between the quinuclidine-borane catalyst and the carbonyl substrate. A scale-up reaction using a continuous-flow photoreactor has also been demonstrated.