Synthesis of pyrazino[1,2-b]indazoles via cascade cyclization of indazole aldehydes with propargylic amines

A cascade annulation of indazole aldehydes with propargylic amines has been developed to synthesize pyrazino[1,2- b ]indazoles under additive-free conditions. Some pyrazino[1,2- b ]indazoles exhibit significant antifungal activity.