Synthesis and thermolysis of N‐heteroarylacetylazides and α‐oximino‐α‐(N‐heteroaryl)acetylazides

Abstract Treatment of N ‐heteroarylacethydrazides with an equimolar amount of nitrous acid afforded N ‐heteroaryacetylazides and subsequent thermolysis of these azides gave the analogues of 2,3‐dihydroimidazo[1,5‐ a ]pyridin‐3‐one. When some of these cyclized compounds were treated with nitrous acid, the ring opening reaction occurred and recyclized 3‐( N ‐heteroaryl)‐1,2,4‐oxadiazolin‐5‐ones were obtained. Treatment of N ‐heteroarylacethydrazides with two equivalent moles of nitrous acid afforded α‐oximino‐α‐( N ‐heteroaryl)acetylazides. Thermolysis of these azides gave mixtures of 3‐( N ‐heteroaryl)‐1,2,4‐oxadiazolin‐5‐one and 3‐hydroxy‐4‐( N ‐heteroaryl)furazan. On the basis of the effects of heterocyclic rings and solvents upon the relative yield of two types of the products, one plausible mechanistic explanation for the decomposition of such azides was proposed. α‐Oximino‐α‐( H ‐heteroaryl)acetylazides were converted into cyano N ‐heterocycles by the action of alkali in good yields.