The general procedure for the synthesis of 3-bromomethylbenzaldehyde from 3-cyanobenzyl bromide was as follows: first, intermediates 60 and 61 were synthesized via α-bromomethyl-toluenesulfonic acid.The specific operation consisted of slowly adding DIBAL-H (1.4 eq., 1.0 M in THF) to a solution of α-bromomethyl-toluenesulfonic acid (15.3 mmol) in toluene (30 mL) at 0 °C over a period of 30 min. The reaction mixture was continued to be stirred at 0 °C for 2 h and then poured into a mixture of 40 mL of dichloromethane and 100 mL of 10% HCl. After stirring for 1 h, the organic layer was separated and washed sequentially with water and brine. The aqueous layer was extracted twice with dichloromethane. The organic layers were combined, dried with Na2SO4, filtered and concentrated to give a semi-oil product, which was stored in a refrigerator to give the final 3-bromomethylbenzaldehyde as a white crystalline solid in quantitative yield. Subsequently, the resulting 3-bromomethylbenzaldehyde was reacted with acetone in ethanol according to the method described in Scheme 4 to give compound 61 as a light yellow crystalline solid. The product was analyzed by ESI MS, m/z: 420.9 [M + H]+; 1H NMR (400 MHz, CDCl3) δ: 7.71 (d, 2H, J = 16.0 Hz, H-1,5), 7.63-7.60 (m, 2H, aryl ring H), 7.54-7.50 (m, 2H, aryl ring H), 7.44-7.37 (m, 4H aryl ring H), 7.08 (d, 2H, J = 16.0 Hz, H-2,4), 4.50 (s, 4H, -CH2Br).
