C(O[C:4](=[O:20])[C:5]([C:18]#[N:19])=[CH:6][NH:7][C:8]1[CH:13]=[CH:12][C:11]([O:14][CH3:15])=[C:10]([O:16][CH3:17])[CH:9]=1)C.C1C=CC(C2C=CC=CC=2)=CC=1.C1C=CC(OC2C=CC=CC=2)=CC=1>CCCCCC>[CH3:15][O:14][C:11]1[CH:12]=[C:13]2[C:8](=[CH:9][C:10]=1[O:16][CH3:17])[NH:7][CH:6]=[C:5]([C:18]#[N:19])[C:4]2=[O:20]A mixture of 2-cyano-3-(3,4-dimethoxyphenylamino)acrylic acid ethyl ester (from Step A, 40 g, 145 mmol) and Dowtherm A (1.2 L) was heated to reflux and allowed to stir under nitrogen atmosphere for 10 hours. The resultant reaction mixture was then allowed to cool to 50° C. and diluted with hexane. The resultant suspension was filtered and the collected solid was sequentially washed with hexane and methylene chloride, then dried in vacuo to provide 6,7-dimethoxy-4-oxo-1,4-dihydroquinoline-3-carbonitrile as a brown solid (21.1 g, 63%). mp 330-350° C. dec; 1H NMR (DMSO-d6)δ 12.57 (s,1H), 8.59 (s, 1H), 7.44 (s, 1H), 7.03 (s, 1H), 3.89 (s, 3H), 3.87 (s, 3H); MS (ES+) m/z 231.0 [M+H].
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