3,4-Dithia-7H-cyclopenta[a]pentalene

25796-77-4

389-58-2

General procedure for the synthesis of cyclopentylbithiophene from 4H-cyclopenta[2,1-B:3,4-B']dithiophen-4-one: Compound 77 (96 mg, 0.499 mmol), hydrazine monohydrate (268 mg, 5.35 mmol), potassium hydroxide (294 mg, 5.249 mmol), and ethylene glycol (5 mL) were added to a pre-dried and corked test tube in a pre-dried and corked test tube. The mixture was slowly heated from room temperature to 190 °C and refluxed at this temperature for 13 hours. Upon completion of the reaction, the mixture was cooled to room temperature, water was added and the organic phase was extracted with ether. The organic phase was washed sequentially with water and brine, dried with anhydrous magnesium sulfate and subsequently concentrated under reduced pressure. Purification by silica gel column chromatography (eluent: hexane/ethyl acetate = 10:1, v/v) afforded cyclopentylthiophene K (59 mg, 66% yield) as a white solid. Compound K was characterized as follows: oxidation potential of 0.68 V and reduction potential of -2.88 V measured by cyclic voltammetry (CV); maximum absorption wavelength of 310 nm in the UV-visible absorption spectrum; thin-layer chromatography (TLC) Rf=0.7 (unfolding agent: hexane/ dichloromethane=2:1, v/v); 1H NMR (270 MHz, CDCl3) δ: 7.17 (d, 2H, J=4.8 Hz), 7.09 (d, 2H, J=4.8 Hz), 3.54 (s, 2H); gas chromatography-mass spectrometry (GC-MS, EI) m/z: 178 (M+).