A facile synthesis of 10-methoxy-4,8-dinitro-6H-benzothieno[2,3-c]chromen-6-one

3-Methoxy-5-nitrobenzaldehyde undergoes Knoevenagel reaction with malonic acid to give 3-methoxy-5-nitrocinnamic acid (I). Treatment of I with thionyl chloride yielded 3-chloro-5-methoxy-7-nitrobenzo[b]thiophene-2-carbonyl chloride (II) in 45 % yield. The reaction of II with 2-nitrophenol in benzene gave 2-nitrophenyl 3-chloro-5-methoxy-7-nitrobenzo[b]thiophene-2-carboxylate (IIIa) in 65 % yield. Finally, dehydrochlorinative photocyclization of IIIa in acetone in the presence of the base triethylamine afforded 10-methoxy-4,8-dinitro-6H-benzothieno[2,3-c]chromen-6-one (IVa). Thus, a series of derivatives IVa-i were synthesized in excellent yields. The structures of the obtained products were characterized by IR and 1H-NMR spectroscopy, as well as elemental analysis. Their purity was ascertained by chromatographic analysis. All the compounds were tested for their antibacterial activity against S. aureus, E. coli, B. subtilis and S. typhosa.