Catalyst- and solvent-free regiospecific S N H Ar phosphinylation of pyridines with H -phosphinates mediated by benzoylphenylacetylene.

Pyridines undergo a facile S N H Ar phosphinylation with H -phosphinates under catalyst- and solvent-free conditions (50-55 °C) in the presence of benzoylphenylacetylene to afford 4-phosphinylpyridines in up to 68% yield. In this reaction, benzoylphenylacetylene activates the pyridine ring by the formation of a 1,3(4)-dipolar complex, deprotonates H -phosphinates to generate P-centered anions and finally acts as an oxidizer, being eliminated from an intermediate ion pair. Terminal electron-deficient acetylenes (methyl propiolate and benzoylacetylene) are inefficient as mediators in the above S N H Ar process.