3-Ethylphenol → 4-Ethyl-2-hydroxybenzaldehyde

Titanium(IV) chloride (100 mL, 100 mmol, 1M in CH2Cl2) followed by dichloromethyl methyl ether (7.47 mL, 82.5 mmol) was added to a cooled 0° C. solution of 3-ethylphenol (6.11 g, 50 mmol). The reaction mixture was stirred for 45 mins. The mixture was poured into ice and extracted with EtOAc. The organic layers were washed with brine, dried over Na2SO4 and concentrated to a bright pink oil. Purification by flash column chromatography (0% to 10% EtOAc in hexanes) gave 4-ethyl-2-hydroxy-benzaldehyde (4.9 g, 65%) followed by 2-ethyl-4-hydroxy-benzaldehyde (1.32 g, 18%). A: 1H NMR (400 MHz, CDCl3): δ 1.25 (t, J=7.6 Hz, 3H), 2.67 (d, J=7.6 Hz, 2H), 6.82 (s, 1H), 6.85 (d, J=8.0 Hz, 1H), 7.46 (t, J=8.0 Hz, 1H), 9.83 (s, 1H), 11.05 (s, 1H). B: 1H NMR (400 MHz, CDCl3): δ 1.27 (t, J=7.6 Hz, 3H), 3.03 (d, J=7.6 Hz, 2H), 6.68 (s, 1H), 6.78 (s, 1H), 6.82 (d, J=8.3 Hz, 1H), 7.77 (t, J=8.3 Hz, 1H), 10.10 (s, 1H).