Chlorosulfonic acid → 7-Chlorosulfonyl-3,4-dihydro-1H-isoquinoline-2-carboxylic acid 2,2,2-trichloro-ethyl Ester

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Reaction Steps

Crude 3,4-dihydro-1H-isoquinoline-2-carboxylic acid 2,2,2-trichloro-ethyl ester (D6) (46 g, 150 mmol) was added dropwise over 40 minutes to chlorosulphonic acid (70 ml) cooled with an ice bath to maintain the temperature between 5 and 15° C. The mixture was then allowed to warm to room temperature, stirred for 16 hours, then poured onto crushed ice (500 ml) and dichloromethane (500 ml) added. This mixture was washed with water (3×250 ml), and brine (50 ml) then dried (sodium sulphate), filtered and evaporated to an orange oil which slowly crystallised on standing. This was recrystallised from ether-hexane to give the title compound (D7) as a white crystalline solid (64.5 g 83%); δH (CDCl3) ppm 3.03 (2H, app.t), 3.81-3.86 (2H, m), 4.74-4.85 (4H, m), 7.42 (1H, d), 7.82-7.88 (2H, m).

Provenance & Evidence