One-Pot Synthesis of 2,5-Bis(3-indolyl)-3,4-dinitrothiophene, 3-(2-Chloro-3,4-dinitrothien-2-yl)indole and Related Congeners

Direct interaction of indolylzinc chloride with 2,5-dichloro-3,4-dinitrothiophene (4) produced 2,5-bis(indol-3- yl)-3,4-dinitrothiophene (5) together with 3-(5-chloro-3,4-dinitrothien-2-yl)indole (6). Interaction of the latter compound with 1-methylpiperazine gave 3-[4,5-di(4-methylpiperazin-1-yl)-3-nitrothien-2-yl]indole (7), as the expected SN-Ar (addition-elimination) di-substitution product, together with 3-[5-(4-methylpiperazin-1-yl)-3-nitrothien-2-yl]indole (8), a mono-substituted product. The formation of 8 probably proceeds via an anomalous pathway, related to cine-substitution, with departure of the nitro group at C-4'. Compound 4 underwent SN-Ar substitution reaction with 1-methylpiperazine to give the respective 2,5-di-(4-methylpiperazin-1-yl)-2,4-dinitrothiophene (9).