Tetrachlorophthalic anhydride → 2,3,4,5-Tetrachloro-6-[4-(diethylamino)-2-methylbenzoyl]benzoic acid

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Reaction Steps

A mixture of tetrachlorophthalic anhydride (21.4 g.), N,N-diethyl-m-toluidine (41 g.), aluminum chloride (30 g.) and o-dichlorobenzene (90 ml.) was heated (75°-95° C.) during one to two hours, then diluted with ice-water. The o-dichlorobenzene layer was separated and steam distilled. The residue was heated with dilute sulfuric acid. The mixture was poured onto ice and made alkaline. The resulting oil was heated in concentrated sulfuric acid. Dilution with water and purification of the product with toluene and hexane afforded 2-(2-methyl-4-(diethylamino)benzoyl)-3,4,5,6-tetrachlorobenzoic acid (IV: Y2 = CH3, Y'4 = (CH3CH2)2N, Z4 = Z"5 = Z"6 = Z7 = Cl) (26 g., m.p. 117° C. with sublimation).

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