General procedure for the synthesis of 3-ethylbenzaldehyde from m-bromobenzaldehyde and triethylboron: To a suspension containing m-bromobenzaldehyde (0.370 g, 2.00 mmol), Pd(dppf)Cl2 (14.6 mg, 20.0 μmol), and CsOAc (0.384 g, 2.00 mmol), protected by argon, triethylborane (1.00 M in THF, 2.00 mL, 2.00 mmol) and THF (3.0 mL). The mixture was heated to reflux and held for 6 hours. After completion of the reaction, it was cooled to room temperature, diluted with ether, washed sequentially with saturated aqueous NaHCO3 and brine, dried over anhydrous Na2SO4, filtered and concentrated in vacuum. The residue was purified by silica gel fast column chromatography to afford 3-ethylbenzaldehyde (0.123 g, 0.920 mmol, 46% yield) as a colorless oil.1H-NMR (CDCl3, 400 MHz) δ: 1.28 (t, J = 7.2 Hz, 3H, -CH3), 2.74 (q, J = 7.2 Hz, 2H, -CH2-), 7.42 -7.48 (m, 2H, Ar-H), 7.69-7.72 (m, 2H, Ar-H), 10.0 (s, 1H, -CHO); the data are consistent with those reported in the literature (Wang et al., 2009).
