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A solution of crude 2,3-dichloro-5-formylpyridine and (carbethoxymethylene)triphenylphosphorane (2.14 g, 5.83 mmol) in toluene (12 mL) was heated at reflux overnight and then cooled to room temperature. After solvent removal at reduced pressure, the residue was chromatographed (9% to 10% EtOAc/hexane) to give 323 mg (16% from 5,6-dichloro-3-pyridinemethanol) of ethyl(E)-3-(5,6-dichloro-2-pyridinyl)-2-propenoate as a white solid, mp 102-103° C. IR 2914, 1702, 1428, 1193 cm−1; 1H NMR (CDCl3) δ 1.37 (t, J=7.2 Hz, 3H, OCH2CH3), 4.31 (q, J=7.2 Hz, 2H, OCH2CH3), 6.53 (d, J=16.2 Hz, 1H, CH═CHCO), 7.62 (d, J=16.2 Hz, 1H, CH═CHCO), 7.94 (d, J=1.8 Hz, 1H, 4-ArH), 8.44 ppm (d, J=1.8 Hz, 1H, 2-ArH). HRMS calcd C10H9Cl2NO2 [M+H]+ 246.0083. found 246.0086.

1. temperatureat reflux overnight
2. customAfter solvent removal at reduced pressure
3. customthe residue was chromatographed (9% to 10% EtOAc/hexane)