Ethoxalyl chloride → Ethyl 3-(3,5-dibromo-4-hydroxyphenyl)-1,2,4-oxadiazole-5-carboxylate

関与物質

反応手順

Ethyl 2-chloro-2-oxoacetate (12.3 g, 82 mmol) was added dropwise to a stirred solution of 3,5-dibromo-N′,4-dihydroxybenzimidamide (25.5 g, 82 mmol) in pyridine (120 mL) and the mixture was stirred at room temperature for 1 hour and then at 60° C. for 2 hours. The resulting suspension was poured onto water (1.5 L) and extracted with ethyl acetate (2×400 mL). The combined extracts were washed with saturated sodium chloride, dried (MgSO4) and evaporated in vacuo to give an oily solid that was purified by flash chromatography to give a colourless powder. Crystallisation from toluene (400 mL) gave the title compound (I 4.7 g, 46%) as colourless crystals. 1H NMR δ (ppm) (DMSO-d6): 1.14 (3H, t), 4.49 (2H, q), 8.14 (2H, s), 10.93 (1H, br s).

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