Shining Light on the Light-Bearing Element: A Brief Review of Photomediated C–H Phosphorylation Reactions

Abstract

Organophosphorus compounds have numerous useful applications, from versatile ligands and nucleophiles in the case of trivalent organophosphorus species to therapeutics, agrochemicals and material additives for pentavalent species. Although phosphorus chemistry is a fairly mature field, the construction of C–P(V) bonds relies heavily on either prefunctionalized substrates such as alkyl or aryl halides, or requires previously oxidized bonds such as C=N or C=O, leading to potential sustainability issues when looking at the overall synthetic route. In light of the recent advances in photochemistry, using photons as a reagent can provide better alternatives for phosphorylations by unlocking radical mechanisms and providing interesting redox pathways. This review will showcase the different photomediated phosphorylation procedures available for converting C–H bonds into C–P(V) bonds.1 Introduction1.1 Organophosphorus Compounds1.2 Phosphorylation: Construction of C–P(V) Bonds1.3 Photochemistry as an Alternative to Classical Phosphorylations2 Ionic Mechanisms Involving Nucleophilic Additions3 Mechanisms Involving Radical Intermediates3.1 Mechanisms Involving Reactive Carbon Radicals3.2 Mechanisms Involving Phosphorus Radicals3.2.1 Photoredox: Direct Creation of Phosphorus Radicals3.2.2 Photoredox: Indirect Creation of Phosphorus Radicals3.2.3 Dual Catalysis3.3 Photolytic Cleavage4 Conclusion and Outlook

Applications of Halogen-Atom Transfer (XAT) for the Generation of Carbon Radicals in Synthetic Photochemistry and Photocatalysis

“…The underutilization of photochemical strategies in XAT settings is notable, considering the vast amount of literature applying photoredox conditions as a mild way to generate related P-radicals via HAT or SET oxidation. − This blueprint, in contrast, has been implemented in many P-radical additions to olefins but, to the best of our knowledge, not in XAT reactivity.…”

Photocatalytic Late-Stage C–H Functionalization

“…Photocatalyzed methods have been developed to advance the field of C−P V bond formation, to date dominated by the venerable Michaelis− Arbuzov reaction (C(sp 3 )−P V bond) and Hirao coupling (C(sp 2 )−P V bond). 282 In 2017, Konig and co-workers synthesized aryl phosphonates via direct C−H phosphonylation of electron-rich arenes (73.1) and heteroarenes using [Ru-(bpz) 3 ][PF 6 ] 2 as photocatalyst, ammonium persulfate as oxidant, and trialkyl phosphites (73.2) as stable and widely available phosphorus source (Scheme 73A). 283 Electron-rich arenes bearing ethers, Boc-amines and halide moieties underwent phosphonylation with diethyl phosphite in moderate to excellent yields (36−99%).…”

Advances in radical phosphorylation from 2016 to 2021

“…In recent decades, along with the rapid development of radical chemistry, the construction of X-P (X=C, N, O or S) bonds with P-centered radicals, which can be easily generated through single-electron transfer (SET) or hydrogen atom transfer (HAT) using metal salts, peroxides, photocatalysts and others, has created a new avenue for the construction of organophosphorus compounds. As a consequence, the past few years have witnessed a renewed awareness regarding the utilization of P-centered radicals in constructing vitally important organophosphorus compounds [6][7][8][9][10][11] . The main characteristic of non-planar P-centered radicals with a variable degree of s-character (especially those containing P=O bonds) is their high reactivity in undergoing radical addition to unsaturated compounds [Figure 1] [12] .…”

“…For example, Gao et al [6,8] reviewed the phosphorus radical-based difunctionalization of unsaturated compounds in 2017 and 2018. Cai et al [9] published a review on visible light-mediated C-P bond formation reactions in 2019, while Chen et al [10] summarized recent advances in the construction of phosphorus-substituted heterocycles in 2020. In 2021, Ung et al [11] reviewed photomediated C-H phosphorylation reactions.…”