Allenylphosphonium salts

Allenyl- and propargyl-phosphonium salts have also been used as precursors of heterocyclic compounds in the presence of various functionalized nucleophiles279, via the intermediacy of vinylphosphonio compounds however, an ylide extrusion has been sometimes observed815,816, depending on the nature of the functions in the nucleophile (reaction 250). Allenylphosphonium salts are able to add such weak CH acids as in ketones, even in absence of basic catalysts817,818, without any modification of the keto group (reaction 251). 

The addition of nucleophiles to prop-2-ynyltriphenylphosphonium bromide (142) proceeds via the allenylphosphonium salt (143) to give the substituted vinylphos-phonium salts (144). The salts formed by addition of primary amines to (143) exist, in many cases, exclusively in either the enamine (145) or imine (146) tautomers,... 

The addition of butanol or diethylamine to the allenylphosphonium salt (148) is reported to form the substituted allylphosphonium salts (149), which undergo acid hydrolysis to form (150). ... 

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