Synthesis of peri-annelated heterocyclic systems based on 3-substituted 1-aryl-4,6-dinitro-1H-indazoles

A method for the synthesis of peri-annelated trinuclear heterocycles, including 14-electron heteroaromatic systems, namely, 1H-thiopyrano4,3,2-cd]indazoles and 1,5-dihydropyrazolo3,4,5-de]cinnolines, from 3-R-1-aryl-4,6-dinitro-1H-indazoles was developed. The method is based on the high mobility of the NO₂ group in position 4 and consists of either selective nucleophilic substitution of the 4-NO₂ group on treatment with the HSCH₂CO₂Me—K₂CO₃ system followed by intramolecular cyclization of the resulting sulfide (R = CHO) or the corresponding sulfone (R = CN) formed upon its oxidation or direct intramolecular substitution of the 4-NO₂ group (R = CH=NNHPh).