2-Amidinylindole-3-carbaldehydes: synthesis of new tetracyclic compounds containing the pyrrolo[1,2-c]1,4-diazepine ring

2-Amidinylindol-3-carbaldehydes bearing an α-alkoxycarbonyl substituent on the cyclic-tertiary amine moiety were prepared. Pyrolysis of these amidines in diethylenglycol-monoethyl ether produced mainly a pyrrolo[1′,2′-1,2]-1,4-diazepino[5,6-b]indol-7,11-dione. A similar result was obtained starting from 2-amidinylbenzofuran-3-carbaldehyde.