General procedure for the synthesis of 2,3,6,7-tetrahydrobenzo[1,2-b:4,5-b']difuran from 1,4-dibromo-2,5-bis(2-chloroethoxy)benzene: 10.50 g (26.6 mmol) of 1,4-dibromo-2,5-bis(2-chloroethoxy)benzene was dissolved in 250 mL of anhydrous tetrahydrofuran under the protection of nitrogen and the solution was cooled to 0°C. Using a syringe equipped with a large gauge needle, a 2.5 M hexane solution of n-butyllithium (23.52 mL, 2.2 eq.) was quickly (within 7 seconds) added to the rapidly stirred solution. The reaction mixture was continued to be stirred for 10 minutes before the solvent was removed under vacuum. The residue was partitioned between ethyl acetate and water and the organic phase was dried over anhydrous sodium sulfate and concentrated to give the crude product. The crude product was purified by silica gel column chromatography (eluent was petroleum ether 60-90 °C: ethyl acetate = 20:1) to afford the target product 2,3,6,7-tetrahydrobenzo[1,2-b:4,5-b']difuran (3.47 g, 80% yield) as white crystals. The product was confirmed by NMR hydrogen spectrum (300 MHz, CDCl3): δ 6.63 (2H, s), 4.52 (4H, t, J=8.6 Hz), 3.13 (4H, t, J=8.5 Hz); NMR carbon spectrum (75 MHz, CDCl3): δ 154.12 (C), 125.93 (C), 105.88 (CH). 71.51 (CH2), 30.31 (CH2).
![2,3,6,7-Tetrahydro-benzo[1,2-b:4,5-b']difuran](/CAS/GIF/81926-24-1.gif)