Substituent effects on the regioselectivity of maleamic acid formation and hydrogen chloride addition to N-aryl maleimides


Abstract: Itaconic anhydride reacts with aryl amines to give a substituent controlled equilibrium mixture of regioisomeric (Z)-2-methyl- and (Z)-3-methyl-4-oxo-4-(arylamino)but-2-enoic acids. Electron-donating groups favor nucleophilic attack on C-5 carbonyl, while the presence of electron-withdrawing groups enhances the bias for attack on C-2 carbonyl. The treatment of (Z)-2-methyl- and (Z)-3-methyl-4-oxo-4-(arylamino)but-2-enoic acids with SOCl_2-Et_3N in THF provided the corresponding maleimides in high yields while under the same conditions the maleic anhydride aryl amine addition products gave predominately the corresponding 3-chloro-1-arylpyrrolidine-2,5-diones and maleimides in substituent dependent ratio.

Keywords: Cyclic anhydrides, maleimides, chlorosuccinimides, LFERs, substituent effect

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