Triphenyl(3-phenylprop-1-ynyl)phosphonium bromide (3) was isolated. This compound is a third isomer for the tautomeric system triphenyl(3-phenylpropadienyl)phosphonium bromide (1) ⇌ triphenyl(3-phenylprop-2-ynyl)phosphonium bromide (2). Salts 1 and 2 smoothly react with secondary amines to give adducts with an α,β-double bond, while salt 3 changes to an allene ylide. Addition of phenylhydrazine and triphenyl(phenylethynyl)phosphonium bromide to salts 1 and 2 and addition of dimethylformamide to salt 2 were performed.

This study identifies a new tautomeric quaternary phosphonium salt, triphenyl(3-phenylprop-1-ynyl)phosphonium bromide (3), as a potential intermediate in the synthesis of,-double bond adducts

Paper

Reactions of tautomeric quaternary phosphonium salts based on triphenylphosphine and 3-phenylpropargyl bromide with nitrogen nucleophiles

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