Triggering the Directional Selectivity of a Ring-Closure Reaction Leads to Pyridoazacarbazoles with Anticancer Properties

We herein describe a facile and versatile synthetic route to the tetracyclic system of 6‐substituted 5,6‐dihydro‐11H‐pyrido[3,2‐i]‐1‐azacarbazoles with promising anticancer properties. These derivatives are built up by an elegant one‐step base‐catalyzed synthetic procedure from commercially available building blocks. One additional step provides the corresponding skeleton hitherto unknown in the literature. The possibility to synthesize a large library of compounds with various substitution patterns utilizing this method underlines the importance of this synthetic procedure. One step to success! Just one step and a facile and efficient synthetic procedure leads to 5,6‐dihydro‐11H‐pyrido[3,2‐i]‐1‐azacarbazoles with highly potent antitumor activity. The aromatic substituent is cleaved easily gaining access to the corresponding hitherto unknown tetracyclic scaffold (see scheme; DMPU=1,3‐dimethyl‐3,4,5,6‐tetrahydropyrimidin‐2‐(1H)‐one).