[Cl:1][C:2]1[CH:7]=[CH:6][N:5]=[C:4]2[CH:8]=[C:9]([C:11]([O-:13])=O)[S:10][C:3]=12.[Li+].C(Cl)(=O)C(Cl)=O.O/[N:22]=[C:23](\[NH2:25])/[CH3:24]>CN(C=O)C.C(Cl)Cl.C1(C)C(C)=CC=CC=1.N1C=CC=CC=1>[Cl:1][C:2]1[CH:7]=[CH:6][N:5]=[C:4]2[CH:8]=[C:9]([C:11]3[O:13][N:25]=[C:23]([CH3:24])[N:22]=3)[S:10][C:3]=12To a mixture of lithium 7-chlorothieno[3,2-b]pyridine-2-carboxylate (2.125 g, 9.7 mmol) and DMF (20 drops) in CH2Cl2 (35 mL), oxalyl dichloride (1.3 ml, 15 mmol) was added dropwise. The mixture was stirred at RT for 2.5 h and then was concentrated to give a yellow solid. The resultant crude acid chloride and (Z)—N′-hydroxyacetamidine (1.4 g, 19 mmol) were heated at 140° C. in xylene/pyridine (6/1, 35 mL) for 1 h. The mixture was diluted with CH2Cl2, and then washed with water, then sat. NaHCO3 and brine. The crude product was purified via column chromatography on silica gel (RediSep 120 g column, gradient elution with 0-50% EtOAc in Hexane) to afford 7-chloro-2-(3-methyl-1,2,4-oxadiazol-5-yl)thieno[3,2-b]pyridine as a white solid.
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