Electron-Deficient Acetylenes as Three-Modal Adjuvants in S Reaction of Pyridinoids with Phosphorus Nucleophiles.

Publications covering a new easy metal-free functionalization of pyridinoids (pyridines, quinolines, isoquinolines, acridine) under the action of the system of electron-deficient acetylenes (acetylenecarboxylic acid esters, acylacetylenes)/-nucleophiles (phosphine chalcogenides, -phosphonates) are reviewed. Special attention is focused on a S reaction of the regioselective cross-coupling of pyridines with secondary phosphine chalcogenides triggered by acylacetylenes to give 4-chalcogenophosphorylpyridines. In these processes, acetylenes act as three-modal adjuvants (i) activating the pyridine ring towards -nucleophiles, (ii) deprotonating the P-H bond and (iii) facilitating the nucleophilic addition of the -centered anion to a heterocyclic moiety followed by the release of the selectively reduced acetylenes (-alkenes).