[CH3:1][O:2][C:3]([C:5]1[S:6][C:7]([C:11]2[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=2)=[CH:8][C:9]=1[NH2:10])=[O:4].CO[C:19]([CH3:21])=[CH2:20].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][CH:14]=[CH:13][CH:12]=2)=[CH:8][C:9]=1[NH:10][CH:19]([CH3:21])[CH3:20])=[O:4]To a stirred solution of 3-Amino-5-phenyl-thiophene-2-carboxylic acid methyl ester (1.82 g, 7.8 mmol) in 1,2-dichloroethane (40 mL) was added sequentially 2-methoxypropene (3.0 mL, 31.2 mmol), AcOH (1.8 mL, 31.2 mmol) and NaBH(OAc)3 (3.31 g, 15.6 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 5% EtOAc-hexane furnished 3-Isopropylamino-5-phenyl-thiophene-2-carboxylic acid methyl ester (2.07 g, 96% yield). 1H NMR (CDCl3, 400 MHz): δ 7.62 (d, 2H), 7.40 (m, 3H), 6.91 (s, 1H), 3.84 (s, 3H), 3.71 (m, 1H), 1.35 (d, 6H).
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