4,9-dimethoxy-1H,3H-naphtho[1,8-cd][1,2,6]oxadiborinine-1,3-diol

n-Butyllithium (0.289 mL, 0.723 mmol) was added to a solution of 1,8-dibromo-2,7-dimethoxynaphthalene (0.100 g, 0.289 mmol) in dry THF (4 mL) under argon at -78 °C. The mixture was stirred for 30 minutes. Trimethyl borate (0.071 mL, 0.636 mmol) was then added quickly and the mixture slowly warmed to r.t. The mixture was stirred for 30 min, quenched with 20 % HCl (2 mL) and left to stir for 15 min. The product was extracted with EtOAc (3 x 4 mL), washed with brine (3 x 4 mL), dried (MgSO4) and the solvent removed in vacuo. The compound was recrystallised from CH2Cl2 – Et2O to give the product as a white solid (10.2 mg, 14 %): 1H NMR (600 MHz, CDCl3): 4.07 (6H, s, H1), 7.19 (2H, d, J 9.0, H2), 7.35 (2H, s, H4), 7.96 (2H, d, J 9.1, H3); 13C NMR (150 MHz, CDCl3): 56.2 (C1), 110.1 (C2), 123.7 (C), 134.4 (C3), 144.0 (C), 165.4 (C); 11B NMR (CDCl3): 29.82; m/z (ES+): 259.3 [M+H+]; HRMS: Calcd for C12H1310B2O5 257.1022, found 257.1017.