Aluminum chloride (160 g, 1.2 mol) was added to a stirred solution of the 4-n-pentylbiphenyl (224 g, 1 mol) in methylene chloride (1000 mL) at approximately -20°C. Then Oxalyl chloride (96 mL) was added to the solution at a temperature below -10°C. After addition, the reaction temperature was allowed to rise to approximately 0°C. Stirring continued at approximately 0°C untill the evolution of hydrogen chloride was ceased. The resulting reaction mixture was poured into ice water forming two nonmiscible fluid layers. The organic layer was seperated from the aqueous layer, washed with water, and dried over anhydrous sodium sulfate. The solvent was removed by distillation to yield a crude 4-n-pentylbiphenyl-4’-carboxy chloride (213 g, 75%) which was used directly in the nextstep.
The 4-n-pentylbiphenyl-4’-carboxy chloride (142 g, 0.5 mol) was reacted with a hot, stirred solution of sodium hydroxide (60 g, 0.75 mol) in water (50 mL) and acetone (500 mL) for about three hours. The cold reaction mixture was then acidified with concentrated hydrochloric acid solution. The acid was filtered and washed with water untill the filtrate was neutralized. The product of the reaction was purified from ethanol to yield 4-n-pentylbiphenyl-4’-carboxylic acid (102.4 g, 80%).
To citraconic anhydride (22.4 g, 0.2 mol) was added from a pipet exactly 4 mL (0.22 mole) of distilled water. The mixture was stirred on a hot plate until a homogeneous solution was formed, then covered with a watch glass and allowed to stand for forty-eight hours. At the end of this time the mixture would solidified completely. For further purification it was finely ground in a mortar, washed with 50 mL of cold benzene, dried in the air, and then dried for twenty-four hours in a vacuum desiccator over phosphorus pentoxide to give citraconic acid (24.4 g, 94%) which melts at 92~93°C.
Reference: Organic Syntheses. Coll. Vol. 2, 140