A phosphonium ylide as a visible light organophotoredox catalyst

Abstract

A phosphonium ylide-based visible light organophotoredox catalyst has been designed and successfully applied to halohydrin synthesis using trichloroacetonitrile and epoxides. An oxidative quenching cycle by the ylide catalyst was established,...

Visible-Light-Driven C–H Imidation of Arenes and Heteroarenes by a Phosphonium Ylide Organophotoredox Catalyst: Application to C–H Functionalization of Alkenes

“…In conjunction with the significant growth of modern photoredox catalysis, organophotoredox catalysis has attracted increasing attention as a powerful tool for sustainable organic synthesis . In 2021, we reported the first example of phosphonium ylide-catalyzed photoredox reactions that proceed under visible-light irradiation . Phosphonium ylide 1a (R 1 = Me, R 2 = H, Ar = Ph) acts as an excited-state reductant ( E * ox = −2.36 V vs SCE, τ = 2.0 ns), enabling C–H functionalization reactions, including C–H imidation of arenes, with the use of N -acyloxyphthalimide ( E red = −1.26 V vs SCE), via oxidative quenching (Scheme ).…”

“…At the outset of our study, we attempted the imidation of mesitylene ( 3a ) using N -acyloxyphthalimide 2 (Table ). Based on our previous report, the reactions were carried out in the presence of phosphonium ylide 1 (10 mol %) using 10 equiv of arene 3a in acetonitrile (0.02 M) at 25 °C for 24 h under blue LED irradiation. The initial experiment using 1a afforded a 65% (NMR) yield of the desired product 4a , along with a 33% (NMR) yield of phthalimide (entry 1).…”

“…In summary, we have developed visible-light-driven C−H imidation of various arenes and heteroarenes by a phosphonium ylide organophotoredox catalyst. 18 Introduction of bulky substituents into the catalyst structure of 1 led to improved catalytic activity. This protocol could be expanded to the trihalomethylative lactonization of alkenes bearing a carboxylic moiety.…”

Tetraarylphosphonium salt-catalyzed formal [3+2] cycloaddition between epoxides and trichloroacetonitrile for the synthesis of β-amino alcohol derivatives

“…This devised approach would not only grant an efficient entry to regioselective β-amino alcohol synthesis, but also provide a new aspect for the utility of TCAN in the organic synthetic chemistry community. 11 Notably, this formidable challenge inspired us to probe a novel application of TAPS as an interesting nucleophilic organocatalyst. 12…”

“…On the other hand, byproduct 3a was presumably formed by HCl addition to epoxide 1a because TCAN was likely to decompose to generate hydrogen chloride via a chlorine radical. 11 After several trials, the addition of molecular sieves 4A and 2-methyl-2-butene resulted in a satisfactory yield (entry 12).…”