[N:1]1[CH:6]=[CH:5][C:4]([CH:7]=O)=[CH:3][N:2]=1.[CH3:9][O:10][C:11]([CH:13]=P(C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1)=[O:12].O>ClCCl>[CH3:9][O:10][C:11](=[O:12])[CH:13]=[CH:7][C:4]1[CH:5]=[CH:6][N:1]=[N:2][CH:3]=1To a solution of pyridazine-4-carboxaldehyde (3.646 mmol, 1 eq) in dry dichloromethane (25 ml), (methoxycarbonylmethylene)triphenylphosphorane (5,550 mmol, 1.2 eq) was added portionwise. The reaction mixture was stirred at room temperature overnight. Reaction mixture was poured into water (200 ml) and extraction with DCM (3×100 ml) followed. Organic layers were combined, dried over phase separator cartridge to giving crude product which was purified on Biotage SP1 Snap Si 100; 40 ml/min in the gradient of MeOH in DCM: 0-10% in 30 CV. The appropriate fractions were combined and evaporated in vacuo to give the required product 3-pyridazine-4-yl-acrylic acid methyl ester (4.142 mmol, yield=89%, purity=96%). [M+H]+=165.11 1H NMR (300 MHz, CDCl3) δ/ppm 3.82 (s, 3H), 6.64-6.68 (m, 1H), 6.72 (s, 1H), 9.22 (dd, J=5.3, 1.0 Hz, 1H), 9.27 (s, 2H)
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