3,5-Dimethoxybenzyl alcohol → 3,5-Dimethoxybenzaldehyde

Alcohol 4 (17.5 g, 0.11 mol) in CH2Cl2 (50 mL) was added slowly to a dry stirred suspension of freshly prepared pyridinium chlorochromate (33.64 g 0.16 mol) in CH2Cl2 (100 mL) at 0.degree. C. The reaction mixture was stirred for 2 h at rt after which the solvent was removed under reduced pressure on a rotatory evaporator. The residue from the reaction mixture was washed with diethyl ether (3×150 mL) and then filtered. The organic filtrate was diluted with a saturated aq solution of NaHCO33 (250 mL) and extracted with EtOAc (3×250 mL). The combined organic extracts were dried (Na2SO4) and concentrated in vacuo. The crude oil was purified by FCC (10% ethyl acetate in hexane) to afford a yellow solid aldehyde 5 (16.4 g, 95%): 1H NMR (300 MHz, CDCl3) δ 9.92 (1H, s, HCO), 7.03 (2H, d, J=2.4 Hz HAr), 6.72 (1H, t, J=2.4 Hz, HAr), 3.87 (6H, s, H3 CO). The spectral data for 5 were in excellent accord with data previously reported on it (Seidel et al., 1990).1 This material was employed directly in the later step.