Advances in 2H-azirine chemistry: A seven-year update

Abstract 2H-Azirines are versatile building blocks for the preparation of various nitrogen-containing heterocycles. Seven years ago the comprehensive review on azirine chemistry was published in Tetrahedron. Since then, there had been an explosion of research activities in the field of these strained molecules. This renaissance is primarily associated with the discovery of new reactivity of azirines and in particular new catalytic and light-induced reactions, which made possible unusual transformations of this three-membered N-heterocycle into azole and azine derivatives as well as polyheterocyclic systems. The second reason for the progress of azirine chemistry is the development of methods for the preparation of new azirine derivatives. The third reason is the discovery of new synthetic equivalents of azirines, which permitted avoiding the use of unstable azirines in some modern catalytic procedures. In the present comprehensive review, we have placed particular emphasis on discussing the new developments in the synthesis and reactivity of azirines for the period from 2012 until the end of 2018.