[N:1]1[S:5][N:4]=[C:3]2[CH:6]=[C:7]([C:10](O)=[O:11])[CH:8]=[CH:9][C:2]=12.C(N(CC)CC)C.C(OC(Cl)=O)C(C)C.[BH4-].[Na+]>O1CCCC1>[N:1]1[S:5][N:4]=[C:3]2[CH:6]=[C:7]([CH2:10][OH:11])[CH:8]=[CH:9][C:2]=12Benzo[1,2,5]thiadiazole-5-carboxylic acid (2.00 g, 11.11 mmol) was dissolved in tetrahydrofuran (50 mL) and cooled to 0° C. To this was added triethylamine (1.80 mL, 12.87 mmol) followed by isobutylchloroformate (1.62 mL, 12.40 mmol) in a dropwise manner. The resulting slurry was stirred for a further 30 minutes at 0° C. and then filtered into a mixture of sodium borohydride (0.83 g, 21.84 mol) in ice water (20 mL). The resulting mixture was stirred at 0° C. for 30 minutes, evaporated to one quarter of its volume and then extracted with dichloromethane (3×50 mL). The organic phases were combined and then dried over sodium sulfate. This was followed by concentration under reduced pressure to provide the desired product as a white solid which was used without further purification (1.50 g, 81%).
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