Sulfur Dioxide → 2-Acetyl-8-chlorosulfonyl-7-chloro-1,2,3,4-tetrahydroisoquinoline

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Reaction Conditions

Reaction Steps

2-Acetyl-8-amino-7-chloro-1,2,3,4-tetrahydroisoquinoline (0.04 mole) in concentrated hydrochloric acid (8.4 ml.) is cooled to 3° C. and treated with sodium nitrite (0.044 mole) dissolved in water (6 ml.). After stirring for 30 minutes, the reaction is tested for nitrous acid with starch/iodide paper. If the test for nitrous acid is negative, more sodium nitrite is added in small portions with stirring over a period of time until the test is positive. When a positive reaction is obtained, magnesium chloride (0.032 mole) is added and the resulting mixture is added to a mixture of acetic acid (40 ml.) saturated with sulfur dioxide and cuprous chloride dihydrate (0.0129 mole) maintained at 30° C and stirred. After about 30 minutes, the mixture is diluted with water (60 ml.) and extracted with ether. The extract is then washed with dilute aqueous sodium bicarbonate/sodium carbonate solution at pH 8-9, then with water, and dried over sodium sulfate. The ether is evaporated to yield 2-acetyl-8-chlorosulfonyl- 7-chloro-1,2,3,4-tetrahydroisoquinoline. 2-Acetyl-8-chlorosulfonyl-7-chloro-1,2,3,4-tetrahydroisoquinoline (0.022 mole) is treated with concentrated ammonium hydroxide (30 ml.) with cooling. The resulting solid is filtered off and washed with water to give 2-acetyl-7-chloro-8-sulfamyl-1,2,3,4-tetrahydroisoquinoline.

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