Ammonium Chloride → 3-Bromo-5-(diethoxymethyl)-2-nitrothiophene

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To a solution of 4-bromo-5-nitrothiophene-2-carbaldehyde (Int. 65) (6.981 g, 29.6 mmol) in EtOH (50 ml), ammonium chloride (0.475 g, 8.87 mmol) and triethyl orthoformate (7.39 ml, 44.4 mmol) were added, and the resulting solution was stirred at 60° C. for 14 hours. Additional triethyl orthoformate (7.39 ml, 44.4 mmol) was added, and the mixture was vigorously refluxed for further 2 days. The solvent was evaporated under vacuum and the crude was partitioned between water and EtOAc. The organic phase was washed with brine, dried over sodium sulfate, filtered and evaporated. The crude was purified by chromatography on silica gel cartridge (petroleum ether/EtOAc=9/1) to afford 3-bromo-5-(diethoxymethyl)-2-nitrothiophene (Int. 66) (7.456 g, 24.04 mmol).

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