Dimethyl Sulfate → m3OMG

To a stirred mixture of sodium borate decahydrate (borax, 80 g) in H2O (1 L) was added methyl gallate (3, 15.0 g, 82 mmol) at rt. After stirring for 1 h, dimethyl sulfate (30 ml, 317 mmol) and NaOH (50 ml, 6.5 M) were added dropwise simultaneously via separate addition funnels over the course of 1 h. After stirring an additional 12 h, the methylation was terminated with H2SO4, (65 ml, conc.) and stirring continued an additional h. The product was removed by extraction with DCM (5×500 ml, each time stirring the solution for 20 min). The combined DCM extracts were washed with brine (300 ml), dried, concentrated in vacuo, and the residue crystallized from methanol-benzene to afford methyl ether 4 (13.7 g, 85%) as a light tan solid, mp 110–111° C., (lit. mp 110–111° C., Pettit and Singh, 1987); 1H-NMR (300 MHz): 3.89 (3H, s, —OCH3), 3.94 (3H, s, —OCH3), 5.40 (2H, bs, —OH), 5.80 (2H, bs, —OH), 7.22 (1H, d, J=1.8 Hz, ArH), 7.35 (1H, d, J=1.8 Hz, ArH).