N‐Heterocyclic Carbene/Cobalt Cooperative Catalysis for the Chemo‐ and Regioselective C−N Bond Formation between Aldehyde and Amines/Amides

• Published in: ChemCatChem Vol. 12; no. 17; pp. 4281 - 4287
• Main Authors: Siddiqui, Asher M., Khalid, Anam, Khan, Arif, Azad, Chandra S., Samim, Mohd, Khan, Imran A.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 04.09.2020
• Subjects: Activation; Aldehydes; Amides; Amines; Aqueous solutions; Breslow's Intermediate; Catalysis; Catalysts; Ethylenediaminetetraacetic acids; Hydrogen bonds; Hydrogen peroxide; Imides; N-heteroatom carbene; Oxidizing agents; Regeneration; Regioselectivity; SET oxidant
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.202000156

A novel methodology for the construction of various secondary (4 examples), tertiary amides (31 examples), and imides (16 examples) by a Cobalt(II) catalyzed oxidative amide coupling in aqueous media. The Co(III)‐TMC was reacted with N‐Heteroatom Carbene to form active catalyst Co(II)NHC‐TMC in situ which involves in the coordination with Breslow's intermediate and SET for the activation of aldehyde and amides. The mechanism for activation of amide and amine differs on the basis of SET based nucleophilic addition and ligand exchange respectively. The regeneration of the catalyst was achieved using Fe(III)(EDTA)‐H2O2 as oxidant. The use of Co(II)TMC‐O2 was also found equally efficient in the process. The method is found regioselective for N−H activation in the presence of equally susceptible ortho‐C−H bond activation. And amines were found more susceptible then the corresponding amide for the reaction. Oxidative amide coupling: A novel methodology for the construction of various secondary (4 examples), tertiary amides (31 examples) and imides (16 examples) by a metal catalyzed oxidative amide coupling in aqueous media, has been devised using in situ generated Co(II)(L)(NHC) based catalytic system and Fe(III)(EDTA)‐H2O2 as oxidizing agent. The method is regioselective for N−H activation in presence of equally susceptible ortho‐C−H bond activation.