Hydrochloric Acid → (5-Bromo-2-chlorophenyl)(4-ethoxyphenyl)methanone

Participants

Reaction Steps

To a stirred suspension of commercial 5-bromo-2-chlorobenzoic acid (250 g, 1.06 mol) in 450 mL of CH2Cl2 containing oxalyl chloride (1.1 mol) was added 1.5 mL of DMF. Once the vigorous evolution of gas ceased, the reaction was stirred overnight prior to removal of the volatiles under vacuum using a rotary evaporator. After dissolving the crude 5-bromo-2-chlorobenzoyl chloride in 200 ml of CH2Cl2, the yellow solution was transferred to a 2 L 3-neck flask equipped with an overhead stirrer and an internal thermometer. The stirred mixture was cooled to −3° prior to adding phenetole (130 g, 1.08 mol). AlCl3 (140 g, 1.07 mol) was added via a solid addition funnel over 30 min to insure that the temperature did not exceed 4°. The copious amounts of HCl gas which began to evolve after 60% of the AlCl3 had been added were trapped by passing the gas over a stirred conc. NaOH solution. HPLC revealed the reaction to be 95% complete 10 minutes after the addition was finished. After the mixture was stirred at 4° for 1 hr, the reaction was quenched by pouring over ice. Subsequently, the suspension was diluted with H2O (1 L ) and extracted 3× with CH2Cl2. The combined organic extracts were washed 2× with 1N HCl, 1× with H2O, 2× with 1M NaOH, and 2× with brine prior to drying over Na2SO4. After removal of the volatiles, HPLC revealed the residue to be a 1:7 mixture of ortho/para isomers. Recrystallization 2× from 400 mL of absolute EtOH yielded 230 g (64%) of 5-bromo-2-chloro-4′-ethoxybenzophenone.

Provenance & Evidence