Ammonium Chloride → Dimethyl 4-cyano-1,3-benzenedicarboxylate

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To a solution of 4-bromoisophthalic acid dimethyl ester 202 (2.95 g, 10.8 mmol) in anhydrous DMF (50 ml), Copper(I) cyanide (1.20 g, 13.5 mmol) was added in one portion. The slurry solution was heated at reflux temperature for one hour. When the solution was cooled to ambient temperature, it was poured into 300 mL of ammonium chloride solution (10%) at 0° C. White precipitate was formed. The slurry solution was stirred at ambient temperature for 30 minutes. Then it was extracted with ethyl acetate. The combined extracts were dried over sodium sulfate. Removal of solvent gave white solid which was washed with cold methanol to give 1.89 g (80%) of 4-cyanoisophthalic acid dimethyl ester 203: 1H NMR (400 MHz, CDCl3) δ 3.95 (s, 3H), 4.05 (s, 3H), 7.91 (d, J=8 Hz, 1H), 8.30 (dd, J=1.7 Hz, J=8 Hz, 1H), 8.77 (d, J=1.7 Hz, 1H).

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