A direct route from white phosphorus and fluorous alkyl and aryl iodides to the corresponding trialkyl- and triarylphosphines

Abstract

Reactions of white phosphorus (P₄), fluorous alkyl iodides I(CH₂)_mR_fn (R_fn = CF₃(CF₂)_n−1; 4.0–5.0 equiv./P), and SmI₂ (1.0–1.5 equiv./iodide) in THF afford the corresponding trialkylphosphines P((CH₂)_mR_fn)₃ (m,n = 2,8; 2,10; 3,6; 3,8; 4,8; 58–92% after workup). Similar reactions with the fluorous aryl iodides IC₆H₄(3-R_f6), IC₆H₄(4-R_f6), and IC₆H₃(3,5-R_f6)₂ require the stronger reductants SmBr₂ or SmCl₂ and give the triarylphosphines P(C₆H₄(3-R_f6))₃, P(C₆H₄(4-R_f6))₃, and P(C₆H₃(3,5-R_f6)₂)₃ (23–41%). These transformations involve non-chain radical additions to P₄. Advantages versus existing routes to fluorous phosphines, and general strategic issues in the synthesis of organophosphorus compounds, are discussed.