ABSTRACT

Cycloadditions of azazulenes such as 1-aza-, 1,3-diaza-, 3a-aza-, 4-aza-, and 5-azaazulenes including their oxo derivatives with acetylenic esters are reviewed; the periselectivity dependent, a Diels-Alder type cycloaddition or a dipolar cycloaddition, and the regioselectivity dependent were observed upon the nature of the substituents and/or the reaction conditions. The reactions of the azaazulenes with diphenylcyclopropenone, heterocumulenes (ketenes, nitrones,  and  isocyanates)  are  also  described. Cycloadditions of fused heterocycles incorporating an azaazulene ring are also referred.