Dimethyl 4-aminophthalate

This acid is isolated in the form of its dimethyl ester by the arsenation of dimethyl-4-aminophthalate according to Bart s method. The ester on hydrolysis gives the sodium salt, which is converted to the silver salt and the latter treated with concentrated hydre chloric acid to obtain the free acid. Fhc free acid separates in clusters of pale yellow crystals... 

The [4 + 2] cycloaddition reaction of 2- or 2,5-substituted iV-methoxycarbonylpyrroles with dimethyl acetylenedicarboxylate is accelerated tremendously by aluminum chloride (70CJC1472). The Diels-Alder cycloaddition is in fact complete in some cases within 30 min at 0 °C if five molar equivalents of A1C13 are utilized. On warming the reaction mixture to 40 °C, the 7-azabicyclo adduct (199) formed initially undergoes rearrangement to an Af-methoxycarbonyl-3-aminophthalate (200 Scheme 42). The overall scheme constitutes a valuable method for the construction of polysubstituted anilines. 

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