Hydrochloric Acid → 4,5-Dichloro-2-({3-chloro-2,4-dihydroxy-5-[4-(methoxycarbonyl)butyl]phenyl}carbonyl)benzoic Acid

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In a 2 L 3-neck round-bottomed flask equipped with a stir and addition funnel was added 4,5-dichlorophthalic anhydride (7.13 g, 32.9 mmol) followed by dry 1,2-dichloroethane (120 ml). After stirring for 30 minutes AlCl3 (11.4 g, 85.54 mmol) was added and the mixture was stirred for another 30 minutes. To this mixture was added via the addition funnel a solution of 5b (8.5 g, 32.9 mmol) with stirring. The solution in the flask became slightly warm and turned dark. Hydrogen chloride gas evolved for about 10 to 20 minutes. Stirring was continued overnight (15-18 hours) at room temperature. During this time, a tarry precipitate formed. To this mixture was added ice (160 g) and concentrated HCl (80 ml) followed by ethyl acetate (900 ml). The content of the flask was stirred until all the solids have completely dissolved. The mixture was transferred to a 2-liter separatory funnel. The organic layer was washed with about 300 ml of 1 N HCl, 2×200 ml of saturated NaCl and dried over sodium sulfate. The solution was filtered and evaporated to a solid, which was then triturated in 200 ml of dichloromethane for 30 minutes, and then cooled to −20° C. for at about 2 h. The crystalline precipitate was filtered off and washed with 2:1 hexanes/dichloromethane, followed by 4:1 hexanes/dichloromethane, and dried to afford 10.8 g (69%) of the desired benzophenone 14b. 1H NMR (DMSO-d6) δ: 12.44 (s, 1H), 10.3 (br s, 1H), 8.14 (s, 1H), 7.87 (s, 1H), 6.88 (s, 1H), 3.55 (s, 3H), 2.44 (t, J=6.8 Hz, 2H), 2.25 (t, J=6.9 Hz, 2H), 1.40 (m, 4H).

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