Reaction Steps
To a stirred solution of thieno(3,2-b)thiophene (5.0 g, 35.7 mmol) in anhydrous THF (120 ml) was added n-butyllithium (2.5 M in hexanes, 12.0 ml, 30.0 mmol) dropwise at −78° C. under nitrogen. After complete addition, the mixture was allowed to warm to room temperature, with stirring, over 2 h, followed by the addition of 3-(6-bromohexyloxymethyl)-3-ethyloxetane (8.38 g, 30.0 mmol). The resultant mixture was stirred overnight at room temperature. The reaction was quenched with sat. aq. NH4Cl, and the reaction mixture was extracted with ethyl acetate (3×70 ml). The combined organic extracts were washed with water, brine, and dried over magnesium sulphate. The solvent was removed under reduced pressure and the residue was purified by column chromatography on silica, eluting with petroleum ether/ethyl acetate (9:1), to give a yellow oil (7.82 g, 77%). 1H NMR (300 MHz, CDCl3): δ (ppm) 7.22 (d, J=5.3 Hz, 1H, Ar—H), 7.14 (d, J=5.3 Hz, 1H, Ar—H), 6.91 (s, 1H, Ar—H), 4.43 (d, J=5.8 Hz, 2H, OCH2), 4.35 (d, J=5.8 Hz, 2H, OCH2), 3.48 (s, 2H, OCH2), 3.41 (t, J=6.4 Hz, 2H, OCH2), 2.84 (t, J=7.4 Hz 2H, ArCH2), 1.35-1.75 (m, 10H, CH2), 0.86 (t, J=7.6 Hz, 3H, CH3); 13C NMR (75 MHz, CDCl3): δ (ppm) 148.3 (quat.), 138.8 (quat.), 137.4 (quat.), 125.4 (CH), 119.5 (CH), 116.3 (CH), 78.6 (OCH2), 73.4 (OCH2), 71.5 (OCH2), 43.4 (quat.), 31.6 (CH2), 31.2 (CH2), 29.5 (CH2), 28.9 (CH2) 26.8 (CH2), 26.0 (CH2), 8.3 (CH3); MS (m/e): 490 (M+, 16%) □305 (79), 223 (25), 205 (100).
