Nucleophilic substitution of hydrogen in pyridine and its derivatives by organophosphorus nucleophiles in the presence of electron-deficient acetylenes

Abstract

The review considers publications on a new easy functionalization of pyridinoids (pyridines, quinolines, isoquinolines, acridine, phenanthridine) by the electron-deficient acetylene (esters of acetylenecarboxylic acids, acylacetylenes, cyanoacetylenes)/P-nucleophile (phosphine chalcogenides, H -phosphonates) system. Particular attention is paid to the SN H reaction of regioselective cross-coupling of pyridines with secondary phosphine chalcogenides, initiated by acylacetylenes and leading to the formation of 4-chalcogenophosphorylpyridines. In these processes, acetylenes act as trimodal adjuvants by (1) activating the pyridine ring towards P-nucleophiles, (2) deprotonating the P-H bond, and (3) facilitating the nucleophilic addition of the P-centered anion to the heterocyclic fragment, followed by the release of selectively reduced (to E -alkenes) acetylenes.