Unexpected synthesis of a novel heterocyclic system – (7E,10aE)-2,7-Dimethylfuro[3′,4′:6,7]cycloocta[1,2,3-cd]indole-8,10(2H,6H)-dione

Abstract The first derivative of a novel heterocyclic system, (7 E ,10a E )-2,7-dimethylfuro[3′,4′:6,7]-cycloocta[1,2,3- cd ]indole-8,10(2 H ,6 H )-dione, was synthesized based on the Stobbe condensation of 3-chloro-1-methylindole-2-carbaldehyde with diethyl isopropylidenesuccinate. Cyclization of the 2-indolyl-containing diacid, formed by subsequent hydrolysis of the condensation product, did not lead to the expected fulgide, but rather to an unprecedented tetracyclic compound, the structure of which was established by 1 H, 13 C NMR, IR spectroscopy, mass-spectrometry and single crystal X-ray diffraction.