Synthesis of a novel tetracyclic pyrido[3',2':4,5]thieno[3,2-b]indole system

Design, Synthesis, and Screening of Pyridothieno[3,2-b]indole and Pyridothieno[3,2-c]cinnoline Derivatives as Potential Biologically Active Molecules

“…The 3-aminothieno[2,3-b]pyridines 1a-o, prepared by alkylation of 4,6-disubstituted 3-cyanopyridine-2-thiones 2a-i followed intramolecular cyclization under basic conditions, were used as starting compounds for the synthesis of corresponding azides (Scheme 1). In our previous work 17 aq solution of KOH (10 %) was used for the intramolecular cyclization of the intermediate S-alkylated products into 3-aminothienopyridines. Now we found that KOH solution is suitable when alkylating agent contains an electron-withdrawing group such nitro-, ester or sulfonamide moiety.…”

“…Azides 5a-q were obtained following a published method 15,17 consisting of successive diazotation of amines 1а-p,r with NaNO2 in a mixture of…”

“…In a previous work, 17 we described only several representatives of the new fused heterocyclic system – pyridothienoindole. In our opinion, an annulation of indole moiety to the thieno[2,3- b ]pyridine framework bearing various alkyl and aryl (hetaryl) substituents will allow to obtain novel derivatives with potential pharmacological activity.…”

“…In this case, the alkylation of thiones 2 and the following heterocyclization occurred in one-pot manner using the described procedure. 17…”

“…13b,14 Earlier, we have exploited the last approach to construct new thieno[2,3-b]pyridines fused with various nitrogen-containing heterocycles, namely, pyridothienodiazepines, 15 thieno[2,3,4i,j]-2,7-naphthyridines 16 and pyrido[3',2':4,5]thieno[3,2b]indoles. 17…”