3,4,5-Trimethoxybenzaldehyde → 5-Ethynyl-1,2,3-trimethoxybenzene

Participants

Reaction Conditions

Reaction Steps

To a flame-dried 50 mL round-bottom flask was added CBr4 (2.54 g, 7.65 mmol). DCM (20 mL) was added and the solution cooled to 0° C. Ph3P (4.01 g, 15.30 mmol) was added and the solution stirred at 0° C. for 15 min. 3,4,5-Trimethoxybenzaldehyde (1.0 g, 5.10 mmol) in DCM (6.0 mL) was added dropwise. The solution was stirred at 0° C. for 5 min. The solvent was removed under reduced pressure, and the resulting oil was filtered through a plug of silica and washed with Hex:EtOAc (9:1, 500 mL; 4:1, 500 mL). The combined organics were concentrated to give the crude dibromo-olefin (2.31 g, 128%), which was dissolved in THF (60 mL) and cooled to −78° C. n-BuLi (13.1 mL, 19.68 mmol, 1.5 M) was added dropwise and the solution stirred at −78° C. for 30 min. Saturated NH4Cl (10 mL) was added and the solution warmed to room temperature. The layers were separated, and the organics were washed with brine (10 mL), dried over anhydrous Na2SO4, and concentrated. The residue was purified by flash chromatography (SiO2, 80 g) using 10% EtOAc in hexanes as the eluent to afford 5-Ethynyl-1,2,3-trimethoxybenzene as a colorless oil (0.770 g, 79%): Rf=0.30 (4:1, Hex:EtOAc); 1H NMR (CDCl3) δ 6.71 (s, 2H), 3.84 (s, 3H), 3.83 (s, 6H), 3.03 (s, 1H); 13C NMR (CDCl3) δ 153.1, 117.1, 109.4, 103.3, 83.8, 76.4, 61.0, 56.2, 56.1; HRFAB [M+Li] 199.0952 (calculated C11H12O3Li: 199.0946).

Provenance & Evidence