tert-Butyl Isocyanide as a Convertible Reagent in Ugi Reaction: Microwave-Assisted Preparation of 5,6-Dihydropyrazolo[1,5-a]pyrazine-4,7-diones - Nikulnikov, Mikhail; Tsirulnikov, Sergey; Kysil, Volodymyr; Ivachtchenko, Alexandre; Krasavin, Mikhail (Synlett, 2009)