[CH3:1][O:2][C:3]([C:5]1[S:6][C:7]([C:11]2[CH:16]=[CH:15][C:14]([F:17])=[CH:13][CH:12]=2)=[CH:8][C:9]=1[NH2:10])=[O:4].CO[C:20]([CH3:22])=[CH2:21].CC(O)=O.[BH-](OC(C)=O)(OC(C)=O)OC(C)=O.[Na+].C([O-])(O)=O.[Na+]>ClCCCl.CCOC(C)=O.O>[CH3:1][O:2][C:3]([C:5]1[S:6][C:7]([C:11]2[CH:16]=[CH:15][C:14]([F:17])=[CH:13][CH:12]=2)=[CH:8][C:9]=1[NH:10][CH:20]([CH3:22])[CH3:21])=[O:4]To a stirred solution of 3-Amino-5-(4-fluoro-phenyl)-thiophene-2-carboxylic acid methyl ester (500 mg, 2.0 mmol) in 1,2-dichloroethane (10 mL) was added sequentially 2-methoxypropene (0.76 mL, 8.0 mmol), AcOH (0.12 mL, 4.0 mmol) and NaBH(OAc)3 (0.848 mg, 8.0 mmol) and stirred for 16 h. It was then diluted with EtOAc and H2O. The aqueous solution was adjusted to pH=7 by adding NaHCO3. The aqueous phase was extracted with EtOAc, the combined extract was washed with brine and dried on MgSO4 and filtered. Purification on bond elute with hexane to 5% EtOAc-hexane furnished 5-(4-Fluoro-phenyl)-3-isopropylamino-thiophene-2-carboxylic acid methyl ester (0.530 mg, 91% yield). 1H NMR (CDCl3, 400 MHz): δ 7.62 (d, 2H), 7.09 (m, 2H), 6.81 (s, 1H), 3.84 (s, 3H), 3.71 (m, 1H), 1.35 (d, 6H).
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