A convenient synthesis of spiroindolo[2,1- b ]quinazoline-6,2′-[1,3,4]oxadiazoles from tryptanthrin and nitrile imines

A convenient method for the synthesis of functionalized spiroindolo[2,1- b ]quinazoline-6,2′-[1,3,4]oxadiazoles from indolo[2,1- b ]quinazoline-6,12-diones and 13 hydrazonoyl chlorides in refluxing MeCN is described. These transformations are highlighted by inert atmosphere and lack of activator or metal promoters. Graphical abstract