Bioinspired Manganese Catalyzed Direct Deamination of Primary Amines With Water Forming Carboxylic Acids and Ketones

ABSTRACT Herein, we are demonstrating an earth‐abundant manganese‐catalyzed oxidative deamination of linear and branched primary amines to selectively form carboxylic acids and ketones using water as the oxygen atom source. A series of pincer and non‐pincer Mn complexes were assessed for these deaminative transformations. A bio‐inspired DAFO (4,5‐diazafluoren‐9‐one) ligand‐based [(DAFO)Mn(CO) 3 Br] complex ( Mn‐1 ) was found to be effective for the reaction proceeding under mildly basic aqueous medium, generating NH 3 and H 2 as sole by‐products without the requirement of any oxidant. An optimized condition of 5 mol% Mn‐1 , Na 2 CO 3 (1 equiv) at 150°C for 48 h in water/1,4‐dioxane mixture furnished 92% of the corresponding benzoic acid from benzylamine. A wide variety of electron‐donating and withdrawing para‐ , meta‐ , and ortho‐substituted benzylamines, including promising hetero and aliphatic linear primary amines, afforded moderate to excellent yield of the desired carboxylate product. We have also examined a few branched primary amines using 5 mol% Mn‐1 and catalytic sodium carbonate at 150°C for 48 h, affording good yield of ketones. The reaction was found to be chemo‐selective for primary amine moieties over alcohol functionalities. Further, stoichiometric mechanistic investigation and preliminary computational data provide insights into the possible mechanistic steps.