First Diels-Alder Reaction of Pyrazolyl Imines under Microwave Irradiation

Abstract

Microwave irradiation in solvent-free conditions induces pyrazolyl 2-azadienes to undergo Diels-Alder cycloadditions with nitroalkenes within 5-10 min to give good yields of pyrazolo[3,4-b]pyridines. This is the first example of a [4 + 2] cycloaddition of a 2-azadiene involving a pryazole ring. By classical heating, these reactions do not occur or afford only traces of the products.