Radical Carbonylation under Low CO Pressure: Synthesis of Esters from Activated Alkylamines at Transition Metal‐Free Conditions

Abstract

High CO pressure (> 40 bar) is usually needed in radical carbonylation reactions in the absence of metal catalyst. In this communication, we developed a transition-metal-free radical carbonylation of activated alkylamines with phenols and alcohols under low CO pressure (1-6 bar). Various esters were obtained in moderate to excellent yields under simple reaction conditions with good functional group compatibility.

Recent Advances in Nickel Catalyzed Carbonylative Reactions via the Insertion of Carbon Monoxide†

“…In 2021, Wu group reported a radical carbonylation under low CO pressure for the synthesis of ester without metal catalyst, [ 19 ] and in 2022, Wu group developed a nickel‐catalyzed four‐component carbonylation of olefins to generate γ‐alkoxy substituted ketones (Scheme 8), [ 20 ] which can be applied to the one‐step synthesis of the drug molecule Naftidrofuryl, indicating its great potential in synthetic chemistry.…”

Base‐Promoted Synthesis of 3‐Alkenyl‐2‐pyridones from N‐Propargyl‐β‐enaminones and Aryl Aldehydes

“…However, the abovementioned methods still have some limitations, such as poor substrate scope, requirement of noble metal as catalysts, and involvement of toxic and hazardous chemicals. With the rise of green chemistry, the development of economical, practical, and transition metal‐free synthetic strategies [ 9 ] for the synthesis of highly functionalized pyridones from readily available substrates is of great significance. In this context, we have recently reported a cascade reaction for the synthesis of 2‐heteroatom substituted pyridines from N ‐propargyl‐β‐enaminones, in which 1,4‐oxazepine anions were proved to be the key intermediates (Scheme 1a).…”

Persulfate promoted carbamoylation of N-arylacrylamides and N-arylcinnamamides with 4-carbamoyl-Hantzsch esters

“…According to the literature 5,10,11 and the above experiments, a plausible mechanism involving a radical process is proposed herein (Scheme 3). 4-Carbamoyl Hantzsch ester 1 is first oxidized by (NH 4 ) 2 S 2 O 8 , generating the carbamoyl radical A via a single electron transfer process.…”

“…4-Carbamoyl Hantzsch ester 1 is first oxidized by (NH 4 ) 2 S 2 O 8 , generating the carbamoyl radical A via a single electron transfer process. 10 Then, radical A reacts with N -methyl- N -phenylmethacrylamide 2a to form alkyl radical B , which further undergoes an intramolecular cyclization with the aromatic ring, leading to an intermediate C . 11 c Finally, the aromatization of intermediate C results in the formation of the desired product 3 with the help of (NH 4 ) 2 S 2 O 8 .…”