Dichlobentiazox synthesis

Yield:957144-77-3 82%

Reaction Conditions:

with triethylamine in acetonitrile at 20; for 5 h;

Steps:

1

To 4.0 g (20.3 mmol) of 3,4-dichloroisothiazole-5-carboxylic acid were added 8 ml of oxalyl chloride and a catalytic amount of DMF, followed by stirring at 50°C for 30 minutes to give rise to a reaction. The reaction mixture was concentrated under vacuum to obtain 3,4-dichloroisothiazole-5-carbonyl chloride. 1.9 g (50.5 mmol) of sodium borohydride was suspended in 40 ml of water. To the resulting suspension was dropwise added, at 10 to 15°C, a solution of the 3,4-dichloroisothiazole-5-carbonyl chloride dissolved in THF (4 ml). Stirring was conducted at 15°C for 30 minutes. Then, an aqueous citric acid solution was added to make the mixture weakly acidic and extraction with ethyl acetate was conducted. The organic layer was washed with water, dried over anhydrous magnesium sulfate, and concentrated. The resulting crystals were washed with hexane to obtain 3.0 g (yield: 81%) of (3,4-dichloroisothiazol-5-yl)methanol as colorless crystals (melting point: 94 to 95°C). ¹H-NMR (CDCl₃) δ: 2.28 (1H, bs), 4.96 (2H, s) ppm In 6 ml of acetonitrile were dissolved 0.62 g (3.10 mmol) of 3-chloro-1,2-benzoisothiazole 1,1-dioxide and 0.57 g (3.10 mmol) of the (3,4-dichloroisothiazol-5-yl)methanol. To the resulting solution was dropwise added 0.34 g (3.4 mmol) of triethylamine, followed by stirring at room temperature for 5 hours to give rise to a reaction. After the completion of the reaction, 12 ml of water was added. The resulting crystals were obtained by filtration. The crystals were washed with water and isopropyl alcohol to obtain 0.89 g (yield: 82%) of 3-(3,4-dichloroisothiazol-5-ylmethoxy)-1,2-benzoisothiazole 1,1-dioxide as a colorless powder (melting point: 165 to 167°C). ¹H-NMR (CDCl₃) δ: 5.79 (2H, s), 7.73-7.94 (4H, m) ppm

References:

EP2017268,2009,A1 Location in patent:Page/Page column 8