Hydrochloric Acid → 2-Methyl-7-chlorosulfonylbenzothiazole

Participants

Reaction Conditions

Reaction Steps

A suspension of 8 g of the product from Example 7 in 20 mL of concentrated hydrochloric acid was cooled to 0° C. and treated with a solution of 3.7 g sodium nitrite in 6 mL of water. After completion of the addition, the mixture was stirred at 0°-5° C. for about 15 minutes. This diazonium salt solution was then added all at once to a mixture of liquid sulfur dioxide, 2 g of cupric chloride dihydrate, and 4 mL water in 39 mL of glacial acetic acid at about 10° C.; vigorous gas evolution ensued. This reaction mixture was stirred at room temperature for another 4 hours, and was then poured into 190 mL ice-water. The resulting precipitate was collected by filtration, washed with water, and dried to give 9.2 g of 2-methyl-7-chlorosulfonylbenzothiazole as a yellow powder, m.p. 93°-97° C., dec; IR(KBr): 1380, 1175, 800, 770, 720 cm-1.

Provenance & Evidence