References
- Author's current address: Shanghai Hutchison Pharmaceuticals, Suite 1107, Hua Sheng Building, 399 Jiu Jiang Road, Shanghai, China P.R., Postal Code: 200001
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- Experimental procedure for the synthesis of 4f (Method A): 1f (0.500 g, 1.06 mmol) was dissolved in 60 mL of DMSO. The solution was heated at 65°C for 16 h. DMSO was removed by GeneVac (Model: HT-12). The resulting crude was purified by semi-preparative HPLC column. 235 mg of 4f was isolated as a TFA salt at a yield of 43.9%. Compound 4f had the same molecular ions as the thiadiazolium cations 1f on the ESI-MS spectroscopy except that 4f had fragment of the benzothiazole. 1H NMR of 6f in acetone-d6 at r.t. showed a typical rotameric splitting of the two ortho-methoxy protons into four peaks and the complexity of the aromatic protons. Upon heating, the 1H NMR of 3f in DMSO-d6 (80°C) showed the collapse of the four methoxy proton peaks into two peaks and the simplification of peaks in the aromatic area. 1H TOCSY NMR in DMSO-d6 at 80°C showed that one of the ortho-protons on the anilinophenyl ring disappeared, indicating ring closure at the ortho-position. 13C-1HMBC, HETCOR, and COSY NMR spectroscopy obtained in DMSO-d6 (80°C) were used to assign the 1H NMR peaks as followed (chemical shifts in ppm):
- Experimental procedure of the synthesis for 4f (Method B): 1f (0.500 g, 1.06 mmol) was dissolved in 10 mL of TEA (0.444 mL, 3.19 mmol) in DMSO. The solution was heated at 65°C for 16 h. DMSO was removed by GeneVac. The resulting yellow crystalline solid was dissolved in 20 mL of saturated aqueous NaHCO3, and was extracted with EtOAc. The organic layers were dried over Na2SO4, and 418 mg (95% yield) of pure 4f was obtained without purification. Anal. calcd: C, 67.84; H, 4.92; N, 10.79; S, 8.23. Found: C, 67.59; H, 4.99; N, 10.60; S, 7.87
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