Oxidative Cleavage and Ammoxidation of Unsaturated Hydrocarbons via Heterogeneous Auto-Tandem Catalysis

Abstract

The oxidative cleavage and functionalization of unsaturated C–C bonds are important processes for synthesis of carbonyl compounds from hydrocarbon feedstocks, yet there has been no report of direct amidation of unsaturated hydrocarbons via an oxidative cleavage of unsaturated C–C bonds with molecular oxygen as an environmentally benign oxidant. Herein, for the first time, we describe a manganese oxide-catalyzed auto-tandem catalysis strategy that enables direct synthesis of amides from unsaturated hydrocarbons by coupling oxidative cleavage with amidation. With oxygen as an oxidant and ammonia as a nitrogen source, a wide range of structurally diverse mono- and multisubstituted activated and unactivated alkenes or alkynes can smoothly undergo unsaturated C–C bond cleavage to deliver one- or multiple-carbon shorter amides. Moreover, a slight modification of the reaction conditions also allows for the direct synthesis of sterically hindered nitriles from alkenes or alkynes. This protocol features excellent functional group tolerance, a broad substrate scope, flexible late-stage functionalization, facile scalability, and a cost-effective and recyclable catalyst. Detailed characterizations reveal that the high activity and selectivity of the manganese oxides are attributed to the large specific surface area, abundant oxygen vacancies, better reducibility, and moderate acid sites. Mechanistic studies and density functional theory calculations indicate that the reaction proceeds through divergent pathways depending on the structure of substrates.

A Mn(II)-Catalyzed Tandem Oxidative Cleavage and Ammoxidation of Alcohols to Primary Amides

“…sis field owing to their unique properties such as multiple oxidation states, high abundance, and low toxicity. 16 Taken together with our previous achievements in the manganese oxide catalyzed tandem oxidative cleavage/ammoxidation of alcohols and alkenes to amides, 11,14 we surmised that the inherent advantages and promising catalytic activity of manganese compounds would make manganese salts a good candidate as a catalyst for the cleavage and ammoxidation of C-C bonds in alcohols. Herein, for the first time, we report an efficient, general, and practical strategy for the direct conversion of alcohols to aromatic primary amides with manganese salt catalytic system.…”

“…As part of our long-time interest in value-added transformation of chemical feedstocks via cleavage and functionalization of C–C bonds, 11 12 13 14 15 we intend to further explore the application of this strategy for amidation of primary and secondary alcohols. Similar to manganese oxides, manganese salts play an indispensable role in the oxidation catalysis field owing to their unique properties such as multiple oxidation states, high abundance, and low toxicity.…”

Cobalt nanoparticles-catalyzed aerobic oxygenation and esterification of alkynes via C≡C bonds cleavage

“… 39 Driven by this work and the previous studies, it is anticipated that the inherent advantages and exceptional catalytic activity would make Co/NC materials a good candidate as a heterogeneous catalyst for the oxidative cleavage and esterification of C≡C bonds in alkynes. In line with our ongoing interest in value-added transformation of chemical feedstocks, 40 , 41 , 42 , 43 , 44 we herein report a novel and efficient method for converting alkynes to esters using heterogeneous Co/NC as catalyst and oxygen as environmentally benign oxidant ( Scheme 1 C). More excitingly, a broad range of mono-, disubstituted alkynes, even aliphatic alkynes, are viable with this method.…”

Regioselective oxidative cleavage of conjugated dienes to access α,β-unsaturated nitriles

“…The oxidation of isolated and conjugated dienes to the corresponding carbonyl 1 and α,β-unsaturated carbonyl compounds, 2 respectively, has been studied as well (Scheme 1b). In the past few decades, several oxidative transformations of isolated CC double bonds into nitrile groups have been achieved in the presence of suitable nitrogen sources, such as ammonia/ammonium salts, 3 nitrites, 4 and azides 5 (Scheme 1a). However, achieving regioselective oxidative cleavage of CC double bonds in unsymmetrical conjugated dienes has proven to be a significant challenge.…”