Switchable radical carbonylation by polarity-regulation

Abstract

Carbonylation reactions involving CO as readily available C1 synthons have become one of the most important tools for construction of carbonyl compounds from feedstock chemicals in modern chemical synthesis. Whereas numerous catalytic methods for carbonylation reactions proceeding via ionic or radical pathways have been reported, an inherent limitation to these methods is the need to control switchable single and double carbonylative formation of value-added products from the same and simple starting materials. Here we describe a new strategy that exploits simple visible-light-driven photoredox catalysis to regulate the polarity of coupling partners to drive switchable radical carbonylation reactions. Controlled trap of various alkyl radicals by single or double CO thereby proceed smoothly with excellent selectivity in the presence of various amine nucleophiles at room temperature, generating valuable amides and α-ketoamides in a versatile and controlled fashion. Combined experimental and DFT computational studies suggest that trap of the initially formed acyl radical by the second molecule of CO to form α-ketoacyl radical is a facile but reversible process; and photoredox-catalyzed SET oxidation of natural nucleophilic amines into relatively electrophilic nitrogen radical cations is responsible for switchable coupling with such two radical intermediates.

Switchable Radical Carbonylation by Philicity Regulation

“…We are convinced that the broad substrate scope, good functional group tolerance, and modularity of this method for the philicity regulation of coupling partners should be of great utility to chemists in both academia and industry . Considering that photochemistry provides an enabling tool for the generation of various radical intermediates that are otherwise difficult to produce in a controlled manner under thermal conditions, many exciting applications of this concept to other related switchable radical carbonylations under visible-light photoredox regimes can be anticipated. , …”

“…58 Considering that photochemistry provides an enabling tool for the generation of various radical intermediates that are otherwise difficult to produce in a controlled manner under thermal conditions, many exciting applications of this concept to other related switchable radical carbonylations under visible-light photoredox regimes can be anticipated. 59…”