A Strategic Advance from Pincer Complexes to Hexadentate‐Co(III) Catalyst for Metal–Ligand Cooperative Activation of Primary Alcohols to Access Highly Functionalized Pyrimidines

Abstract In this report, we present a sustainable, eco‐friendly, practical, and cost‐effective one‐pot three‐component reaction for the synthesis of a diverse library of highly substituted pyrimidines from amidines, primary alcohols, and aromatic ketones, catalyzed by a cobalt(III) complex. The well‐defined cobalt(III) complex Co(III)BPMAP‐OClO 4 is derived from a redox‐active phosphine‐free, pentadentate mono‐carboxamide ligand (BPMAP‐H), and is formed in situ from various cobalt(II) sources, including CoCl 2 ·6H 2 O, CoBr 2 , Co(NO 3 ) 2 ·6H 2 O, Co(OAc) 2 ·4H 2 O via oxygen activation. Using aromatic ketones and benzyl alcohols, a wide range of 2,4,6‐trisubstituted pyrimidines ( TriPym ) and 2,4,5,6‐tetrasubstituted pyrimidines ( TetraPym ) were synthesized (119 examples) in isolated yields of up to 93%. The catalytic system is also applicable to aliphatic ketones and aliphatic primary alcohols, affording 31 additional examples with yields of up to 92%. Control experiments and DFT calculations support a plausible mechanism involving dehydrogenation of the alcohols through a metal‐ligand cooperative pathway.