Hydrochloric Acid → ethyl 1-tosyl-1H-pyrrolo[3,2-c]pyridine-2-carboxylate

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Reaction Conditions

Reaction Steps

A solution of compound 6-b (10 g, 367 mmol) in dry THF (150 mL) was cooled to −70° C. and n-BuLi (CAS 109-72-8) (2.5 M in hexane, 16.7 mL, 41.9 mmol) was added dropwise under N2. The mixture was stirred at −78° C. for 1 hour and then ethyl carbonochloridate (CAS 541-41-3) (fresh redistilled, 4.2 mL, 44 mmol) was added dropwise at −70° C. The mixture was warmed to 20° C. naturally and stirred at 20° C. for 1 hour. Then water (800 mL) was added. The mixture was acidified to pH=4 to 5 with a 1N HCl aqueous solution and extracted with ethyl acetate (400 mL×2). Then the pH of the aqueous layer was adjusted to pH=8 by addition of NaHCO3. The resulting mixture was extracted with ethyl acetate (200 mL). The combined organic layers were washed with brine, dried over Na2SO4 and evaporated. The residue was washed with tert-butylmethyl ether. The solid was dried under high vacuum. The residue was purified by flash column chromatography, eluting with petroleum ether/ethyl acetate (3:2). After evaporation of the fractions, 6-c is obtained (6 g, 47%).

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