Hydrochloric Acid → 3,3''-Dioctyl-2,2':5',2''-terthiophene

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Reaction Steps

0.53 g (21.8 mmol) of magnesium turnings were introduced in a 100 ml flask and suspended in 30 ml of anhydrous diethyl ether. To the resulting suspension, maintained under an argon (Ar) atmosphere, was slowly added a solution of 3.0 g (3.9 mmol) of 2-bromo-3-octylthiophene having formula (1) and 0.93 ml (10.9 mmol) of dibromoethane in 20 ml of anhydrous diethyl ether. The obtained reaction mixture was sonicated for 30 minutes and subsequently heated at the boiling point of the solvent, for 1.5 hours. After the elimination of the excess of magnesium turnings by filtration, the solution containing 2-(3-octylthienyl)magnesium bromide having formula (2), was slowly added, at 0° C., to a mixture of 0.4 ml (3.6 mmol) of 2,5-dibromothiophene and 0.18 g (0.3 mmol) of [1,3-bis(diphenylphosphino)propane]dichloronickel(II) [Ni(DPPP)Cl2] in 30 ml of anhydrous diethyl ether. The resulting reaction mixture was heated at the boiling point of the solvent, for 18 hours, and poured into a mixture of crushed ice and hydrochloric acid (HCl) (2 M) obtaining an organic phase and an aqueous phase which were separated. The aqueous phase was then extracted with diethyl ether (3×20 ml). The overall organic phase (obtained by joining the organic phases obtained as described above) was dried over anhydrous magnesium sulfate (MgSO4), at room temperature (25° C.), for 3 hours. The solvent was subsequently evaporated at reduced pressure and the obtained residue was purified by chromatography on silica gel using petroleum ether as eluent obtaining 1.24 g (67% yield) of 3,3″-dioctyl-2,2′:5′,2″-terthiophene having formula (3), as yellow liquid, which was characterized by 1H NMR (300 MHz, CDCl3) obtaining the following spectrum: 7.18 (d, 2H), 7.05 (s, 2H), 6.94 (d, 2H), 2.77 (t, 4H), 1.65-1.59 (m, 4H), 1.39-1.26 (m, 20H), 0.87 (t, 6H).

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