Propiolic Acids in the Synthesis of N-heterocycles

This review discussed the synthetic applications of propiolic acids in the preparation of diverse N-heterocycles. 3 similar to 9-membered rings like azirines, beta-lactams, oxazolidin-2-ones, 2-oxindoles, indoles, isoindolin-1-ones, imidazo[1,2-a]pyridines, triazoles, 2-pyridones, 2-quinolones, 1,4-benzothiazines, thiazinones, spiroindolines, etc. could be constructed via radical addition, four-component Ugi reactions, 1,3-dipolar cycloadditions, or Diels-Alder reaction mechanism. We hope this review will promote future research in this area: Introduction; Synthesis of azirines; Synthesis of lactams; Construction of five-membered rings; Construction of six- membered rings; Double cyclization for N-heterocycles; Construction of 7 similar to 9membered rings; Conclusion.