1,2‐Diazetidines − Structure, Synthesis, and Functionalization

1,2‐Diazetidines are saturated four‐membered heterocycles featuring two adjacent nitrogen atoms. Despite their promising potential as rigid molecular scaffolds for drug discovery, their synthesis and reactivity remain largely unexplored. This review summarizes their three‐dimensional structural features, which have been characterized using various spectroscopic and crystallographic methods. Current synthetic approaches of 1,2‐diazetidines fall into three main categories: (i) [2 + 2] cycloadditions between azo compounds and electron‐rich olefins, (ii) photochemical ring contraction of dihydropyridazines, and (iii) intramolecular ring closure of hydrazine derivatives, the latter enabling stereocontrol at the four‐membered ring. Finally, the reactivity and functionalization of these cyclic hydrazines are discussed, including derivatization at both nitrogen atoms.