Cobalt-catalyzed cyclization of benzamides with alkynes: a facile route to isoquinolones with hydrogen evolution.

The reaction of benzamides with alkynes assisted by an 8-aminoquinoline ligand in the presence of Co(OAc)2·4H2O and pivalic acid under an air atmosphere provided isoquinolone derivatives in good to excellent yields. In this reaction, the active Co(iii) species is regenerated by the reaction of Co(i) species with pivalic acid under an air atmosphere with hydrogen evolution. The proposed mechanism was supported by competition experiments, deuterium labelling studies, radical scavenger experiments and kinetic studies.