Graphitic Carbon Nitride as Photocatalyst for the Direct Formylation of Anilines

Abstract

We report the use of graphitic carbon nitride (g‐CN) for the photocatalytic radical formylation of anilines, which represents a more sustainable and attractive alternative to the currently used approaches. Our operationally simple method occurs under mild conditions, employing air as oxidant. In particular, the chemistry is driven by the ability of g‐CN to reach an electronically excited state upon visible‐light absorption which has a suitable potential energy to trigger the formation of reactive α‐amino radical species from anilines. Mechanistic investigations also proved the key role of the g‐CN to form reactive superoxide radicals from O2via single electron transfer. Importantly, this photocatalytic transformation provides a variety of functionalized formamides (15 examples, up to 89% yield).

A Guide to Chemical Reactions Design in Carbon Nitride Photocatalysis

“…Being an electron‐deficient substrate, aryldiazonium tetrafluoroborate (reduction potential is only +0.05 V vs. SCE) is reduced easily to the aryl radical [61] . Superoxide radical anion (O 2 ⋅ − ) is another ubiquitous reactive oxygen species, which is generated upon PET from g‐CN excited state to O 2 [62,63] . Electron‐rich aromatic hydrocarbon that is free of benzylic C(sp 3 )−H bonds is oxidized to the corresponding radical cation, [64] because alternative, ES‐PCET involving cleavage of C(sp 2 )−H bond, would be thermodynamically very challenging (see also Figure 5B).…”

Nanostructured electrocatalysts for organic synthetic transformations

“…1 The basic concept is to exploit the electrochemical potential to form highly reactive intermediates, such as radicals and radical ions, from suitable organic precursors through single electron transfer (SET) processes. 2,3–6 In principle, these SET events occur under mild operating conditions and in a controlled fashion, thus avoiding the use of potentially harmful reagents ( e.g. a stoichiometric amount of oxidants/reductants), or harsh conditions as in the case of conventional thermal processes.…”