Dimethyl 4-aminoisophthalate → Dimethyl-4-(2'-isopropoxybenzoylamino)-isophthalate

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Reaction Steps

Dimethyl-4-amino-isophthalate (10 g) in 10 ml of dioxane and 20 ml of anhydrous pyridine are treated with 20 g of 2-isopropoxy-benzoyl chloride at room temperature, overnight. After dilution with water, the precipitate is collected, dissolved in ethyl acetate, and washed with 5% NaHCO3 and then with water. After evaporation to dryness under vacuum, the material is crystallized from isopropyl ether, yielding dimethyl-4-(2'-isopropoxybenzoylamino)-isophthalate (12.3 g; m.p. 107°-110° C.), which is dissolved in 80 ml of dioxane and treated with 80 ml of 1 N NaOH at room temperature for one night. After acidification with dilute HCl, the precipitate is collected under vacuum and washed with water until neutral. The yield is 10.9 g of 4-(2'-isopropoxybenzoylamino)-isophthalic acid, which are treated with 60 ml of acetic anhydride at 90°-100° C. for 15'. After cooling, dilute with 60 ml of isopropyl ether and filter. The yield is 9 g of 6-carboxy-2-(2'-isopropoxyphenyl)-4H-3,1-benzoxazin-4-one (m.p. 246°-250° C.), which are reacted at room temperature first with 90 ml of 32% ammonium hydroxide and then with 45 ml of 2 N NaOH for 120'. After acidification with 4 N HCl, the precipitate is filtered off and crystallized from ethanol-chloroform to give 6-carboxy-2-(2'-isopropoxyphenyl)-3,4-dihydro-4-oxo-quinazoline (6.6 g; m.p. 316°-318° C.).

Provenance & Evidence