2,5-Dichlorobenzophenones can be used as starting materials for general, pharmaceutical and polymer synthesis. For example, using such compounds to prepare substituted para-polyphenylenes should proceed readily by metal-catalyzed aryl coupling of the 2,5-dichlorophenyl group of these compounds. Polyphenylenes formed from these compounds will have pendant side groups comprising the carbonyl, and the aryl or pyridyl group bonded thereto.
To a 22 L, three-necked flask fitted with a thermometer, mechanical stirrer and a Vigreux column connected to an aqueous NaOH scrubbing tower, was added 1,4-dichlorobenzene (3 Kg, 26.4 mol) and benzoyl chloride (2.6 Kg, 18.55 mol). The mixture was heated to 80° C. to give a homogeneous solution. Aluminum chloride (5.5 Kg, 41.25 mol) was added over 12 min. with stirring. (The molar ratio of reactants was 2.2:1.4:1.0 (AlCl3 : Dichlorobenzene: Benzoyl Chloride)). The resulting mixture was heated to 140° C. over 60 min, followed by heating to 175° C. over 30 min. The heating was stopped at 175° C. The mixture was allowed to cool to 80° C. over two hours and poured into a well-stirred mixture of ice and water (ca. 25 L water and 15 Kg of ice) over 30 min. The organic solid was collected by filtration and dissolved in 7 L of toluene. The solution was washed with aqueous sodium bicarbonate and dried. Toluene was removed by distillation. Pure 2,5-dichlorobenzophenone was isolated in 80% yield after recrystallization from hexane and toluene.
[1] Patent: US5210313, 1993, A
[2] Recueil des Travaux Chimiques des Pays-Bas, 1931, vol. 50, p. 753,779
[3] Journal fuer Praktische Chemie (Leipzig), 1933, vol. <2> 138, p. 311
