25796-77-4

51751-44-1

79-44-7

25796-77-4

The general procedure for the synthesis of 4H-cyclopenta[2,1-B:3,4-B']dithiophen-4-one from 3,3'-dibromo-2,2'-bithiophene and dimethylcarbamoyl chloride was carried out as follows: 30 g of diethyl ether was added to a 250 mL three-necked flask under nitrogen protection and cooled to -70 °C by a cryogenic bath with stirring. Subsequently, 20 mL (0.05 mol, 2.5 mol/L) of hexane solution was slowly added, followed by the dropwise addition of 6.28 g (0.02 mol) of diethyl ether solution of Intermediate 1. After addition, the reaction was continued with stirring for 1 hour. Then, 2.58 g (0.024 mol) of N,N-dimethylcarbonyl chloride was added slowly and the reaction was continued with stirring for 3 hours. Upon completion of the reaction, the temperature of the reaction system was raised to 0°C and 20 g of water was added to terminate the reaction. The reaction mixture was partitioned and the organic phase was extracted with ethyl acetate. The organic phases were combined and concentrated under reduced pressure to remove the solvent to give a yellow oil. Finally, 2.88 g of light yellow liquid product was obtained in 75.1% yield by column chromatography separation and purification using petroleum ether: ethyl acetate = 20:1 (v/v) as eluent.