Synthesis of Cobalt Complexes With Thiomorpholine‐Derived N,O‐Bidentate Ligands Featuring N ‐Oxide Units and Catalytic Application in N ‐Alkylation of Aromatic Amines With Primary Alcohols

ABSTRACT The transition‐metal‐catalyzed borrowing hydrogen reaction has emerged as a powerful strategy for constructing chemical bonds, owing to its environmental friendliness and high reaction efficiency. In this study, we have synthesized and characterized two novel cobalt complexes ( Co‐1 and Co‐2 ) bearing new bidentate ligands derived from thiomorpholine and 8‐bromomethylquinoline. X‐ray diffraction analysis reveals that the central cobalt atom in Co‐2 is tetra‐coordinated by one oxygen atom from the thiomorpholine N ‐oxide moiety and one nitrogen atom from the quinoline ring of ligand (L 2 ), along with two chlorine atoms, adopting a regular tetrahedral geometry. The catalytic performance of these cobalt complexes is evaluated in the N ‐alkylation of amines with alcohols via a borrowing hydrogen strategy and Co‐2 exhibits high catalytic activity. Importantly, the aromatic amines and primary alcohols containing different functional groups can be tolerated under present catalytic system. This work provides valuable insights into catalyst design and deepens our mechanistic understanding of this environmentally friendly reaction pathway.