Organic photoredox catalytic α-C(sp³)–H phosphorylation of saturatedaza-heterocycles

Abstract

Photoinduced C(sp3)–H phosphorylation was reported to rapidly install a phosphoryl group on the biologically useful saturated aza-heterocycles with commercially available diarylphosphine oxide reagents by a novel organic photocatalyst.

Organic photoredox catalyzed C(sp3)–H functionalization of saturated aza-heterocycles via a cross-dehydrogenative coupling reaction

“…Based on the mechanistic experiments and our previous investigation, 28–30,38–41 we described a proposed catalytic cycle for this reaction. As shown in Scheme 3, the photocatalyst t Bu-DCQ was irradiated with visible light to deliver the excited photocatalyst *[ t Bu-DCQ] (*[ t Bu-DCQ]/ t Bu-DCQ = 1.38 V), which accepted an electron from cyclic amine 1 ( E ox = 0.74 V versus SCE in CH 3 CN) to form the reduced photocatalyst [ t Bu-DCQ ]˙ − ( III ) and the corresponding amine radical cation IV .…”

“…21,22 Therefore, the direct C(sp 3 )–H functionalization of saturated aza-heterocycles has gained the attention of many scientists in the organic synthesis community. 23–27 Recently, our group as well developed a series of new methods for the α-C(sp 3 )–H acylation, 28 carbamoylation, 29 and phosphorylation 30 of this valuable motif by the development of novel organic photocatalysts. Given the wide distribution of α-indolyl substituted aza-heterocycle analogues among bioactive molecules (Scheme 1a), 31–35 we were intrigued to explore the direct cross-dehydrogenative coupling of saturated aza-heterocycles with unprotected indole.…”

Photocatalytic Hydrogen Atom Transfer-Induced Arbuzov-Type α-C(sp3)–H Phosphonylation of Aliphatic Amines

“…Another powerful method for assembling complex α-aminophosphonates is the Kabachnik–Fields reaction, a three-component phospha-Mannich reaction in which an imine is generated in situ from a carbonyl compound and an amine. Recent studies have demonstrated the phosphonylation of N -aryl tertiary amines under photocatalytic and electrocatalytic conditions, initiated by single-electron oxidation of the tertiary amine. − The oxidative phosphonylation of trialkyl amines was also realized by cobalt catalysis and photocatalysis. , The decarboxylative phosphonylation of amino acids enabled by photocatalysis has been reported as well (Figure C). ,, However, these methods either require preformed imines, only work with a limited scope of simple tertiary amines, use excess amines, are difficult to be applied to late-stage functionalization, or necessitate the presence of a carboxylic acid as a pre-existing functionality. Consequently, a general and mild protocol for α-C­(sp 3 )–H phosphonylation of aliphatic amines, which provides direct access to α-aminophosphonates from a diverse range of amines, remains highly sought after.…”

Photoinduced ligand-to-iron charge transfer enabled C(sp3)–H phosphorylation of hydrocarbons

“…Among various scenarios, the selective installation of a phosphine moiety on C(sp 3 )–H bonds of hydrocarbons is not only an intriguing frontier of contemporary research but also yet to be fully explored. 12 Recently, we disclosed iron-catalyzed C(sp 3 )–H borylation, thiolation, and sulfinylation reactions via a photoinduced ligand-to-metal charge transfer (LMCT) process. 13 The direct excitation of high-valent metal–ligand complexes allowed the generation of reactive chlorine radical species, 14 which could undergo intermolecular hydrogen atom transfer (HAT) with simple alkanes and trigger a series of C(sp 3 )–H functionalization reactions.…”