Synthesis of 1h-1,5,7-triaza- cyclopenta[c,d]phenalenes, a new heterocyclic system

Abstract

In previous work [1-4], we have developed a number of methods for the peri annelation of six-membered rings to give perimidines. In light of the high biological activity of a significant number of indole derivatives, we propose a method for the peri annelation of the pyrrole ring to perimidines. The reaction of ketones 1a-c (1 mmol) and NaN3 (0.07 g, 1.08 mmol) in PPA* (2-3 g) at 70-80°C for 1 h and then at 150-160°C for 4 h monitored by thin-layer chromatography leads to 1H-1,5,7-triazacyclopenta[c,d]phenalenes 3a-c in 36-48% yield. The reaction involves intermediante formation of amides 2a-c, which cam be isolated, for example 2a. The H NMR spectra were taken on a Bruker WP-200 spectrometer at 200 MHz in DMSO-d6 with TMS as the internal standard. The reaction course and purity of the products obtained were monitored on Silufol UV-254 plates with 1:1 ethyl acetate–ethanol as the eluent.