Dichloromethane → N-(3,5-dichlorobenzenesulfonyl)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid, methyl ester

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Reaction Steps

To a mixture of 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid, methyl ester hydrochloride (200 mg, 0.878 mmol) in a 1:1 mixture of CH2Cl2 and THF (2.5 mL each) was added dropwise DIPEA (0.88 mmol, 113 mg) followed by 3,5-dichlorobenzenesulfonyl chloride (0.922 mmol, 227 mg), a second equivalent of DIPEA and 4-DMAP (0.176 mmol, 22 mg). The reaction mixture was stirred at rt overnight when TLC (4:1 hexane:ethyl acetate) indicated disappearance of all starting material. The volatiles were removed in vacuo and the residue was purified by flash column chromatography on silica gel eluted with a gradient of hexane and ethyl acetate to yield N-(3,5-dichlorobenzenesulfonyl)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid, methyl ester (282 mg, 80%) as a white foam, homogeneous by TLC (Rf=0.55, 4:1 hexane:ethyl acetate);

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