2,2'-BITHIOPHENE can be obtained by first preparing a Grignard reagent from 2-bromothiophene, and then coupling it with 2-bromothiophene.
At room temperature, Mg (3.5 g, 0.147 mol) was added to a three-necked flask, a condenser was added, and the reaction apparatus was sealed. The gas was evacuated (Ar gas) 3-5 times. 60 mL of anhydrous diethyl ether was injected into the three-necked flask with a syringe and stirred. Then, compound 4 (20 g, 0.123 mol) and 0.5 mL of 1,2-dibromoethane were added to an empty single-necked flask and dissolved with 30 mL of anhydrous diethyl ether. The reaction flask was then heated with a hair dryer. The dissolved mixture was added dropwise to the reaction flask with a syringe. After the addition was complete, the reaction apparatus was placed at 50 °C for 3 h. Another clean three-necked flask was taken, and compound 4 (16.7 g, 0.1 mol) and Ni(dppp)Cl2 were added to it. A condenser was added, and the reaction apparatus was sealed. The above reaction solution was then transferred to this three-necked flask with a syringe and heated to 50 °C overnight. The reaction solution was extracted with ethyl acetate, and the combined ethyl acetate phases were washed with distilled water and then dried with anhydrous sodium sulfate.
Ethyl acetate was removed by vacuum distillation, and the crude product was purified by silica gel column chromatography (eluent: petroleum ether) to give a white solid, 2,2'-BITHIOPHENE.
