[CH2:1]([O:3][C:4](=[O:15])[CH2:5][CH:6](Br)[C:7](=O)[C:8]1[S:9][CH:10]=[CH:11][N:12]=1)[CH3:2].[CH:16]([NH2:18])=[S:17].C(N)=O.P12(SP3(SP(SP(S3)(S1)=S)(=S)S2)=S)=S>O1CCOCC1>[CH2:1]([O:3][C:4](=[O:15])[CH2:5][C:6]1[S:17][CH:16]=[N:18][C:7]=1[C:8]1[S:9][CH:10]=[CH:11][N:12]=1)[CH3:2]To a solution of 3-bromo-4-oxo-4-thiazol-2-yl-butyric acid ethyl ester (2.2 g, 7.53 mmol) in 1,4-dioxane (40 mL) is added thioformamide (freshly made from formamide and P2S5 in 1,4-dioxane) (22.59 mmol). The mixture is refluxed overnight. The solvent is removed and NaHCO3 (aq.) (40 mL) and DCM (100 mL) are added to the residue. The organic layer is separated and the aqueous layer is extracted with DCM (2×40 mL). The combined organic layers are dried and solvent removed. The crude is purified by column (1% methanol n DCM) to give [2,4′]bithiazolyl-5′-yl-acetic acid ethyl ester.
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