5-Amino-1-vinyl-4,5-dihydro-1H-1,2,3-triazoles as a Source of 1-Amino-2-aza-1,3-butadiene

Thermolysis of 4,4-dimethyl-1-(1-phenylvinyl)-5-(1-pyrrolidinyl)-4,5-dihydro-1H-1,2,3-triazole gave 2-methyl-N-(1-phenylvinyl)-1-(l-pyrrolidinyl)-1-propanimine, which reacted as a 2-azabutadiene with electrondeficient dienophiles to afford the corresponding [4+2] cycloadducts. Reactivity and regioselectivity of the cycloaddition reactions were rationalized with the frontier molecular orbital treatment.