CN(C)/[CH:3]=[CH:4]/[CH:5]=O.[Cl:8][C:9]1[CH:14]=[CH:13][C:12]([C:15](=[O:19])[CH2:16][C:17]#[N:18])=[C:11](F)[CH:10]=1.C(O)(=[O:23])C.C(OCC)(=O)C>CN(C=O)C>[Cl:8][C:9]1[CH:10]=[C:11]2[C:12]([C:15](=[O:19])[C:16]3[C:17]([O:23]2)=[N:18][CH:3]=[CH:4][CH:5]=3)=[CH:13][CH:14]=1
A mixture of (E)-3-(dimethylamino)acrylaldehyde (3.26 g, 32.9 mmol), the product from Step 1 (5.00 g, 25.3 mmol) and acetic acid (7.24 mL, 127 mmol) in DMF (40 mL) was heated to 120° C. for 48 h and cooled to room temperature. Ethyl acetate (400 mL) was added and the mixture washed with saturated NaHCO3 (40 mL), water (40 mL), brine (40 mL), dried (MgSO4) and concentrated. The residue was purified by flash column chromatography (silica, 10-40% ethyl acetate in hexanes) to provide 8-chloro-5H-chromeno[2,3-b]pyridin-5-one (600 mg, 10%). MS (ES+) m/z: 232 (M+H).
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