7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline--hydrogen chloride (1/1) → 7,8-Dichloro-3,4-dihydroisoquinoline

Participants

Reaction Steps

To a mixture of 1 liter 5 percent aqueous sodium carbonate and 62.6 g. (0.233 mole) potassium nitrosodisulfonate was added 21.9 g. (0.092 mole) 7,8-dichloro-1,2,3,4-tetrahydroisoquinoline hydrochloride and then 0.1 liter 5 percent aqueous sodium carbonate. The reaction mixture was stirred at room temperature for 23 hours. The reaction mixture was then extracted with methylene chloride (3×250 ml.). The combined extract was washed with saturated sodium chloride solution, dried over anhydrous magnesium sulfate and filtered. The filtrate was concentrated to dryness under reduced pressure to afford a crude intermediate. The crude intermediate was recrystallized from ethyl acetate to yield 7,8-dichloro-3,4-dihydroisoquinoline as a yellow solid with a melting point of 56°-60° C. 7,8-Dichloro-3,4-dihydro isoquinoline was converted to the desired 7,8-dichloro-1-isopropyl-1,2,3,4-tetrahydroisoquinoline via a Grignard reaction with isopropylmagnesium iodide. 7,8-Dichloro-1-isopropyl-1,2,3,4-tetrahydroisoquinoline hydrochloride has a melting point of 196°-200° C.

Provenance & Evidence