Sodium Carbonate → 2-(2-Thienyl)thiazole

Participants

Reaction Steps

2-Bromothiazole (15.0 g) and 2-thiopheneboronic acid (14.0 g) were dissolved in dimethoxyethane (150 ml). To the mixture was added bis(triphenyl)phosphine palladium(II) dichloride (3.2 g) and 2M sodium carbonate (137 ml), and the mixture was refluxed under argon atmosphere for 2 hours. The mixture was cooled to room temperature, and the reaction solution was diluted with ethyl acetate, and washed with water. The organic layer was collected, dried over sodium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (hexane:ethyl acetate=96:4) to give 2-(2-thienyl)thiazole (9.87 g) as oil. APCI-Mass m/z 168 (M+H) (2) The above compound (3.17 g) was treated in a manner similar to Reference Example 121 to give 5-fluoro-2-(2-thienyl)thiazole (1.58 g) as oil. APCI-Mass m/z 186 (M+H) (3) The above compound (1.58 g) was dissolved in chloroform (16 ml), cooled to 0° C., and thereto was added dropwise a solution of bromine (1.43 g) in chloroform (15 ml). The mixture was stirred at the same temperature for one hour, warmed, and further stirred at room temperature for one hour. The reaction mixture was poured into saturated aqueous sodium hydrogen carbonate solution, and the mixture was extracted with chloroform. The extract was washed with 10% aqueous sodium thiosulfate solution, brine, and dried over sodium sulfate. The solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (hexane:ethyl acetate=97:3) to give 2-(5-bromo-2-thienyl)-5-fluorothiazole (1.81 g) as a pale yellow solid. (4) The above compound (300 mg) and 5-bromo-2-chlorobenzaldehyde obtained in Reference Example 16-(1) were used and treated in a manner similar to Reference Example 7 to give the desired 5-bromo-2-chloro-1-(5-(5-fluorothiazol-2-yl)-2-thienylmethyl)benzene (199 mg) as a pale yellow powder.

Provenance & Evidence