Fluorinated phosphorus compounds: Part 10. Bis(fluoroalkyl) S-alkyl phosphorothiolates and tris(fluoroalkyl) phosphorothionates

Treatment of bis(fluoroalkyl) phosphites (RFCH2O)2P(O)H, where RF was CF3 or C2F5 with sulfur in pyridine at 80 °C gave salts of structure [(RFCH2O)2P(O)SH]NC5H5 in 90 and 88% yield, respectively. The salts reacted with alkyl iodides in acetonitrile at 50 °C to furnish bis(fluoroalkyl) S-alkyl phosphorothiolates (RFCH2O)2P(O)SR, where R was Me, Et, n- and i-Pr (when RF = CF3) and Me (when RF = C2F5). Yields ranged from 21 to 57%. Bis(trifluoroethyl) S-methyl phosphorothiolate (CF3CH2O)2P(O)SMe underwent fluorination by silver(I) fluoride in acetonitrile at room temperature to yield the phosphorofluoridate (CF3CH2O)2P(O)F in 75% yield. Tris(fluoroalkyl) phosphorothionates (RFCH2O)3P = S, where RF was CF3, C2F5 and C3F7, were prepared in 30–34% yield by heating the tris(fluoroalkyl) phosphites (RFCH2O)3P and sulfur to 200 °C in a sealed tube for 8 h.