Photochemical Alkene Hydrophosphination with Bis(trichlorosilyl)phosphine

Bis(trichlorosilyl)phosphine (HP(SiCl3)(2), 1) was prepared from [TBA] P(SiCl3)(2)] ([TBA]2, TBA = tetra-n-butylammonium) and triflic acid in 36% yield. Phosphine 1 is an efficient reagent for hydrophosphination of unactivated terminal olefins under UV irradiation (15-60 min) and gives rise to bis(trichlorosilyl)alkylphosphines (RP(SiCl3)(2), R = (CH2)(5)CH3, 88%; (CH2)(7)CH3, 98%; (CH2)(2)C(CH3)(3), 76%; CH2Cy, 93%; (CH2)(2)Cy, 95%; CH2CH(CH3)(CH2)(2)CH3, 82%; (CH2)(3)O(CH2)(3)CH3, 95%; (CH2)(3)Cl, 83%; (CH2)(2)SiMe3, 92%; (CH2)(5)C(H)CH2, 44%) in excellent yields. The products require no further purification beyond filtration and removal of volatile material under reduced pressure. The P-Si bonds of prototypical products RP(SiCl3)(2) (R = -(CH2)(5)CH3, -(CH2)(7)CH3) are readily functionalized to give further phosphorus-containing products: H3C(CH2)(7)PCl2(56%), [H3C(CH2)(5)P(CH2Ph)(3)]Br (84%), H3C(CH2)(7)PH2 (61%), H3C(CH2)(5)P(O)(H)(OH) (81%), and H3C(CH2)(5)P(O)(OH)(2) (55%). Experimental mechanistic investigations, accompanied by quantum chemical calculations, point toward a radical-chain mechanism. Phosphine 1 enables the fast, high-yielding, and atom-efficient preparation of compounds that contain phosphorus-carbon bonds in procedures that bypass white phosphorus (P-4), a toxic and high-energy intermediate of the phosphorus industry.

Automated summary

The synthesis of bis(trichlorosilyl)phosphine was successfully achieved, and it was found to be an efficient reagent for hydrophosphination of unactivated terminal olefins, yielding bis(trichlorosilyl)alkylphosphines in excellent yields. The product can be further functionalized to obtain phosphorus-containing compounds, offering a fast and atom-efficient synthetic route that bypasses the use of toxic and high-energy white phosphorus. This research holds significant importance in the phosphorus industry.