Visible-Light-Induced Iron Group Metal Catalysis: Recent Developments in Organic Synthesis

Abstract

One central research goal of the modern organic chemistry society is to develop sustainable synthetic methodologies. Visible light-induced transformation applying earth-abundant metals as catalysts is a good reply to the concern. In this short review, recent developments of organic photocatalysis applying iron group metal (Fe, Co, Ni) catalysts are discussed. Reaction types, the catalyst details, and mechanisms are introduced.

Terminal C(sp 3 )–H borylation through intermolecular radical sampling

“…On the basis of mechanistic experiments and prior studies on photocatalysis that used FeCl 3 (34,46), we propose a mechanism for the selective borylation of n-hexane (Fig. 5).…”

“…Mechanistic experiments were carried out to obtain more comprehensive insights. As previously reported (34,46), ultraviolet-visible spectra of the individual reaction components as well as the reaction mixture were acquired to confirm the presence of the [FeCl 4 ] − species as the photocatalyst (fig. S9).…”

“…Iron (III) chloride has been established as a promising precursor for generating chlorine radicals through a photoinduced ligand-to-metal charge transfer (LMCT) process ( 34 ). Our group and others have successfully applied this protocol in several photocatalytic reactions ( 34 , 46 ). In this work, we applied the aforementioned strategy to achieve terminal C(sp 3 )–H borylation of unbranched alkanes and substrates with varying steric hindrance.…”

Iron Photoredox Catalysis–Past, Present, and Future

“…To avoid the problems associated with limited ES-lifetimes necessary for intermolecular electron transfer, one can employ an inner-sphere SET process between the iron center and an in situ-coordinated substrate. − This process is more commonly referred to as visible-light-induced homolysis (VLIH) , and is initiated by the formation of a metal–substrate complex (Figure ). Upon photoexcitation, an inner-sphere electron transfer takes place through a CT state, inducing the cleavage of the metal–substrate bond and the generation of a radical substrate species, which is then able to react further.…”

Visible-light induced FeCl3-catalyzed reductive transamidation of N-acyl benzotriazoles with nitro compounds

“…as photocatalysts garnered increasing attention in terms of sustainability. 14 Specifically, some simple iron salts, which feature the obvious advantages of low cost and inexhaustibility, could catalyze the reductive transformations of nitroarenes under visible-light promoted conditions. 9 d Remarkably, photocatalyzed reductive amidations of nitroarenes with aldehydes, alcohols and alkyl chlorides based on iron catalysts were developed by several other groups.…”