General procedure for the synthesis of 5,6-difluorobenzo[c][1,2,5]thiadiazole from 4,5-difluorophthalimide: To a 500 mL two-necked round-bottomed flask were added 4,5-difluorobenzene-1,2-diamine (10.0 g, 0.070 mol, Matrix Scientific), anhydrous CHCl3 (250 mL) and anhydrous triethylamine ( 40 mL, 0.28 mol). The reaction mixture was stirred until the diamine was completely dissolved. Thionyl chloride (SOCl2, 10.5 mL, 0.145 mol) was added slowly and dropwise through the addition funnel, followed by heating and refluxing the reaction mixture for 5 hours. Upon completion of the reaction, the mixture was cooled to room temperature and poured into 500 mL of distilled water. Extraction was carried out with CH2Cl2 (100 mL x 3), the organic layers were combined and dried with anhydrous MgSO4. The solvent was removed under reduced pressure and the crude product obtained was purified by column chromatography using hexane/ethyl acetate (1:4) as eluent. After removal of the solvent, a brownish white crystalline solid product was obtained. Yield: 10.65 g (90% yield).1H NMR (600 MHz, CDCl3): δ 7.73 (t, 2H, JF.H = 12.0 Hz, 12.0 Hz).
![5,6-difluorobenzo[c][1,2,5]thiadiazole](/CAS/20150408/GIF/1293389-28-2.gif)