[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 (0.502 g, 2.0 mmol) in 1,2-dichloroethane (6.0 mL) was added sequentially 2-methoxypropene (0.38 mL, 4.0 mmol), AcOH (0.114 mL, 2.0 mmol) and NaBH(OAc)3 (0.84 g, 4.0 mmol) and stirred for 2 hrs. 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 10% EtOAc-hexane furnished 5-(4-fluoro-phenyl)-3-isopropylamino thiophene-2-carboxylic acid methyl ester (0.538 g, 92% yield).
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