Aerobic Oxidation of Primary Amines to Imines in Water using a Cobalt Complex as Recyclable Catalyst under Mild Conditions. Issue 59 (1st October 2018)

• Record Type: Journal Article
• Authors: Hazra, Susanta; Pilania, Priti; Deb, Mayukh; Kushawaha, Ajay Kishor; Elias, Anil J.
• Is Part Of: Chemistry. Volume 24:Issue 59(2018)
• Page Start: 15766
• Page End: 15771
• Publication Date: 2018-10-01
• Subjects: aerobic oxidation -- amines to imines -- catalysis -- recyclable catalysts -- water soluble complex; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201803251
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Oxidative coupling of primary amines to imines has been achieved by using a water soluble cobalt complex as catalyst and air as the oxidant at near ambient conditions. Aromatic, heteroaromatic and aliphatic amines were successfully converted to the corresponding imines with yields of up to 96 %. A 20 gram scale reaction for the synthesis of imine from benzylamine in good yield is also demonstrated with this method. The catalyst has been found to be reusable with up to five cycles. It is highly efficient, gives a turnover number (TON) of up to 128, and shows chemoselectivity with the only byproducts being water and ammonia. Control experiments and mechanistic studies indicate that the Co II /Co III catalytic cycle is responsible for these oxidative transformations. Some of the reactive intermediates of this reaction have also been isolated and structurally characterized. Abstract : Co operation : Catalytic activity of the water soluble N, N ′‐bis(2′‐pyridinecarboxamide)‐1, 2‐benzene cobalt complex for oxidation of amines to imines is reported. Reactions occurred at near ambient conditions by using air as the sole oxidant and water as solvent. Ease of preparation of the catalyst using an inexpensive ligand and cobalt salts, its water solubility and reusability are additional interesting features of this methodology.