New applications of pyridinium ylides toward heterocyclic synthesis

The recent advances in the syntheses of various heterocycles based on pyridinium ylides are described. Depending on the reactivity of the pyridinium ylides and the reactants, a significant structural diversity of heterocycles can be prepared. It is evident that the application of pyridinium ylides is the most pertinent for the preparation of fused and spiropyrrole derivatives. Besides, often they are convenient precursors for the preparation of certain substituted non-fused pyrroles, furans, cyclopropanes and polyheterocycles. Particular attention is paid to heterocyclic syntheses involving the in situ formation of ylide precursors and their reaction partners under the multicomponent reaction conditions. The present survey covers studies published for the period from 2012 until the May 2020.