Synthesis of Polyphosphonium Salts

The case of molecular structures with several phosphonium units, the multiphos-phoniums , can be distinguished from the macromolecular structures involving organic polymers with many phosphonium units, called the polymeric phosphoniums . 

For a-halo ketones, bisphosphonium salt formation can also take place by vinylation or arylation of the phosphine (reaction 90). Bisphosphonium salts can also be obtained, in moderate yield, by the introduction of two phosphines on the same aromatic or heterocyclic ring, at high temperature358 (reaction 91). For pyridine, activation by triflic anhydride allows successive additions of two phosphonio groups in the 2,4-positions247 (reaction 92). 

Phosphonium ylides can also be used to prepare from substituted ethynylphosphonium371, 1,3-propenylidenebisphosphonium salts or, more curiously, 1,1-propenylidenebisphos-phonium ylides (reaction 98). 

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