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

Abstract

Phosphonium ylide catalysis through an oxidative quenching cycle has been developed for visible-light-driven C−H imidation of arenes and heteroarenes. The present protocol could be applied not only to trihalomethylative lactonization reactions involving trifluoromethyl, trichloromethyl, and tribromomethyl radicals but also to the first example of an organophotoredoxcatalyzed imidative lactonization reaction involving a nitrogencentered electrophilic radical species.

Synthesis, characterization and stability of phosphonium phenolate zwitterions derived from a (diphenylphosphino)phenol derivative and oxiranes

“…Finally, the O1-P1-C18 angles are between 163° and 165°, and the torsion angle defined by O1-C1-C6-P1 is in all cases less than 7°. The bonding situation in the phenolate ring is similar to what have been found for Michael-acceptor derived zwitterions [28] or for (triphenylphosphonium)phenolate and point to an electron delocalization within a ylidic system [24,35]. The P1-C6 distances in 2a (1.774(4) Å for the conformer with intramolecular hydrogen bonding and 1.780(4) Å for the intermolecular hydrogen bonded molecules) and in 2d (1.778(4) Å) are significantly shorter than the corresponding P-C18 and P-C24 distances and shorter than in the free phosphine 1 (1.825 Å) [38].…”

“…We have chosen a (diphenylphosphino)phenol derivative combining the phenol and the phosphine into a single molecule [20] to study in particular the first step of the reaction and found evidence for the elusive formation of phosphonium phenolate species reminiscent of II. The resulting zwitterionic molecules do not undergo the deoxygenation reaction and are thermally quite stable, making them potentially interesting as catalysts for various reactions such as the synthesis of cyclic carbonates from epoxides and CO 2 [21,22] or organophotoredox catalysis [23,24].…”

Radical reactions enabled by polyfluoroaryl fragments: photocatalysis and beyond

“…The same reagent was used to aminate aromatic compounds and hetarenes using organophotoredox catalysis (Scheme 56). 156,157 Irradiation of 56.1 with an excess of arene 56.2 and photocatalyst leads to the formation of phthalimide-substituted products 56.4 . Similarly to the previous case, the reaction proceeds through addition–oxidation–deprotonation sequence.…”

Trichloromethylative Olefin Lactonization by Photoredox Catalysis

“…Recently, Toda et al reported the lactonization of alkenes using their phosphonium ylide as an organophotoredox catalyst; however, the competitive halolactonization made the product isolation difficult. [5] The limited substrate scope of these precedent reactions in Scheme 1 is also a disadvantage. Thus, trichloromethylative oxygen functionalization of olefin has scope for improvement and investigation.…”