Cyanoacetohydrazides in Synthesis of Heterocyclic Compounds.

Use of cyanoacetohydrazides as precursors in reactions leading to construction of heterocycles is reviewed. In addition to some common heterocyclic compounds, synthesis of other uncommon heterocycles such as thiadiazole, oxadiazole, fused heterocycles, and some seven- and eight-membered heterocycles such as benzodiazepine, oxazepine, and benzoxocine starting with cyanoacetohydrazides and their derivatives is also reported. The main aim of this review is to show the application of cyanoacetohydrazides in heterocyclic synthesis via different types of reaction, including cyclocondensation and cyclization. The results are arranged in terms of the type of heterocycle formed, from five-, six-, seven-, to eight-membered and fused rings. This review aims to cover literature up to 2018, showing the distribution of publications involving use of cyanoacetohydrazides for preparation of heterocycles.