tert-Butyl amides resulting from Ugi MCR of t-BuNC and 5-substituted-1H-pyrazole-3-carboxylic acids with various aldehydes and amines undergo cyclization into 5,6-dihydropyrazolo[1,5-a]pyrazine-4,7-diones in glacial acetic acid under microwave irradiation. This reaction is a remarkable case of neighboring-group-assisted cleavage of tert-butyl amides and demonstrates utility of t-BuNC as a new convertible isocyanide.