55737-77-4

18643-84-0

151900-28-6

55737-77-4

Example 72 Preparation of 3-chloro-4-(methoxycarbonyl)benzoic acid: In a 2L round-bottomed flask equipped with a mechanical stirrer, 2-chloro-1,4-benzenedicarboxylic acid dimethyl ester (25.15 g, 0.11 mol), methanol (300 mL) and tetrahydrofuran (300 mL) were added. A solution of lithium hydroxide monohydrate (4.62 g, 0.11 mol) in water (200 mL) was added slowly over 10 min. After the reaction mixture was stirred overnight at room temperature, the solution was concentrated to about 150 mL by rotary evaporator and subsequently diluted with water (200 mL). The precipitated solid was collected by filtration and washed with cold water (2 x 20 mL) to recover the unreacted starting material, dimethyl 2-chloro-1,4-benzenedicarboxylate (1.8 g), the product being shiny flaky crystals. The combined filtrates were acidified by slowly adding 1N hydrochloric acid (112 mL, 0.112 mol) with stirring. The precipitated solid was collected by filtration, washed with cold water (2 x 50 mL) and air dried. The dried solid was dissolved in methanol (300 mL) and heated to about 45 °C to dissolve completely, followed by the slow addition of water under stirring until the solution approached the cloud point. The solution was allowed to stand at room temperature overnight, and the precipitated colorless solid was filtered and washed sequentially with a cold methanol-water (1:2, 30 mL) mixture and cold water (30 mL). The solid was recrystallized from the methanol-water system as described above and dried to finally obtain 3-chloro-4-(methoxycarbonyl)benzoic acid (13.1 g, 55.5% yield) as colorless needle-like crystals.