Photochemical Benzylation of White Phosphorus

Abstract

Organophosphorus compounds (OPCs) have wide application in organic synthesis, material sciences, and drug discovery. Generally, the vast majority of phosphorus atoms in OPCs are derived from white phosphorus (P 4 ). However, the large-scale preparation of OPCs mainly proceeds through the multistep and environmentally toxic chlorine route from P 4 . Herein, we report the direct benzylation of P 4 promoted by visible light. The cheap and readily available benzyl bromide was used as a benzylation reagent, and tetrabenzylphosphonium bromide was directly synthesized from P 4 . In addition, the metallaphotoredox catalysis strategy was applied to functionalize P 4 for the first time, which significantly improved the application range of the substituted benzyl bromide.

Direct Synthesis of Phosphoryltriacetates from White Phosphorus via Visible Light Catalysis

“…Then a series of experiments were conducted to further explore the mechanism. Without blue light, photocatalyst or NaOAc, the yields diminished obviously, which confirmed that blue light, photocatalyst and NaOAc were important in the reaction system (Table 1, entries [15][16][17]. Adding additional reductants also didn't enhance the yield (Table S4 in the Supporting Information), which was consistent with our mechanism that Br À and NaOAc could act as proper reductants in our system.…”

“…Further screening the concentration of P 4 indicated that 2 mL THF (0.0125 M P 4 ) was optimal (Table 1, entries 12-14). In addition, the lack of blue light, fac-Ir(ppy) 3 or NaOAc led to an obvious decrease in the yield (Table 1, entries [15][16][17]. Therefore, the reaction condition in entry 12 was chosen as the optimal one.…”

“…In 2023, Tang's group also synthesized dialkyl phosphine oxides via the visible‐light induced reaction between alkyl iodides and P 4 [14] . Very recently, we reported the benzylation of P 4 under a photoredox/titanium dual catalytic system to provide tetrabenzylphosphonium bromide efficiently [15] …”

“…[14] Very recently, we reported the benzylation of P 4 under a photoredox/titanium dual catalytic system to provide tetrabenzylphosphonium bromide efficiently. [15] Despite the significance of previous work, introducing more organic synthons to construct OPCs from P 4 directly and selectively is still challenging and desirable. [16][17][18][19][20][21][22][23] According to literature reports, α-bromo esters were common carbon-centered radical precursors in organic synthesis.…”