Compound OP4Br

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InChIKey KQCNLZNWCHZYTD-UHFFFAOYSA-N

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

A hexane solution (17.5 mL) of n-BuLi (1.57 M, 28 mmol) was added at –78 °C under Ar to a THF solution (400 mL) of 2,2'-dibromo-4,4',5,5'-tetramethoxybiphenyl (OP2Br) (10.0 g, 23 mmol), and the mixture was stirred at the same temperature for 30 min. After addition of CuCN powder (1.04 g, 12 mmol), the reaction mixture was allowed to warm to 25 °C and stirred continuously for 2 hours. Then, duroquinone powder (5.70 g, 35 mmol) was added to the resultant solution, and the mixture was stirred at 25 °C for 1.5 hours, poured into an aqueous solution of NH₃, and extracted with AcOEt. The combined organic extract was washed successively with a saturated aqueous NH₄Cl solution and water, dried over anhydrous MgSO₄, and filtered off from an insoluble fraction. The filtrate was evaporated to dryness under a reduced pressure, and the residue was subjected to column chromatography (SiO₂, CH₂Cl₂/AcOEt 95/1 v/v), to allow isolation of OP4Br as white solid (5.70 g) in 70% yield. IR (KBr): ν_max (cm^–1) 2995, 2939, 2907, 2835, 1603, 1496, 1246, 1026, 857, 774. ¹H NMR (500 MHz, CDCl₃): δ (ppm) 6.99 (br., 2H), 6.75 (m, br., 4H), 6.40 (br., 2H), 3.84–3.83 (m, 12H), 3.70 (br., 6H), 3.56 (br., 6H). MALDI-TOF mass: calcd. for C₃₂H₃₂Br₂O₈ [M]⁺: m/z = 704.04; found: 704.00. Anal. calcd. for C₃₂H₃₂Br₂O₈: C, 54.56; H, 4.58. Found: C, 54.91; H, 4.58.