Formamide, N-(2-methylphenyl)- → 3-(2-Methylphenyl)-4,5-dimethylthiazolium chloride

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A mixture of 8b (4.055 g, 30 mmol) and phosphorus pentasulfide (1.351 g, 3.04 mmol) in dry 1,4-dioxane (4 mL) was stirred at room temperature for 15 min under an argon atmosphere. 4-Chloro-2-butanone (2.131 g, 20 mmol) was added and the resulting slurry was heated at 100° C. The reaction mixture was refluxed for 50 min, initially becoming clear yellow and finally deep red. After cooling at room temperature, the crude mixture was diluted with H2O (20 mL). Na2CO3 was added to the reaction mixture until pH≈7. The solvent was evaporated under reduced pressure and the resulting solid was suspended in CH2Cl2 and purified by column chromatography (column packed with silica gel) eluting with EtOH/CH2Cl2 (15/85). Upon concentration of the last yellowish band, a viscous orange oil was obtained. This was solidified when washed under vigorous stirring with diethyl ether (3×2 mL) to afford 9b as a tan solid (1.20 g, 17%). 1H NMR (CD2Cl2, 300 MHz): δ=11.09 (s, 1H), 7.53-7.31 (m, 4H), 2.57 (s, 3H), 2.08 (s, 3H), 2.04 (s, 3H); 13C{1H} NMR (CD2Cl2, 75 MHz): δ=160.77, 142.05, 136.10, 134.60, 134.30, 132.23, 132.00, 128.08, 126.55, 17.23, 12.90, 11.98; HRMS (FAB+) calculated for C12H14NS [M]+ 204.0847, observed 204.0845.

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