Spirophosphonium salts

The formation of phosphine 81 and dimer 80 in the decomposition of 77 does not necessarily prove a radical equilibrium 78a 78b, although phosphoranyl radical 78a was also accessible by treating the open ring lithium compound 82 with less than equivalent amounts of bromine 97). Excess bromine leads to spirophosphonium salt 34-Br which can again be reduced to radical 78 with potassium or sodium metal or electrolytically. The investigation of a series of substituted spirophosphoranyl radicals of that sort containing in all four 4,4 -95) or 5,5 -positions98) methyl,... 

Silyl-substituted phosphonium salts can only be stabilized by non-halogen substituted counter ions, e.g. Co(CO)4 (Scheme 6). Thus iodoethane gives the phosphonium salt from Me3SiPEt2, while condensing 1,4-dichlorobutane with the phosphacyclohexane 1 gives the spirophosphonium salt 2 (equation 4)10. The addition of Me3SiPH2 to vinyl phosphines has been used as a synthetic route to substituted phosphacycloalkanes, notably 3 (equation 5)11. 

The spirophosphonium salt (64) is formed, together with some secondary phosphine oxide (65), when phosphorus trichloride is mixed with diphenyl-amine at 210 °C and the reaction mixture treated with water. ... 

REACTIVITY OF NONCONJUGATED RINGS 8.41.6.1 Spirophosphonium Salts and Ylides... 

---