Synthesis of N-(2, 4, 6-Tribromophenyl)maleimide

Abstract

Synthesis of N- (2, 4, 6-tribromophenyl)maleimide (TBPMI) from maleic anhydride (MAN) and 2, 4, 6-tribromoaniline (TBA) was investigated. Although N-phenylmaleamic acid (PMA) is really p repared by the reaction of aniline (ANL) and MAN, N- (2, 4, 6-tribromophenyl)malearnic. acid (TBPMA)was not obtained by attempted reaction of TBA with MAN even at higher temperature. NPhenylmaleimide (PMI) is produced with a high yield using orthophosphoric acid as catalyst. Unlikely TBPMI was synthesized with only a low yield under similar conditions. However, it was found that TBPMI can be prepared with a high yield in mesitylene under reflux conditions at 168 °C. According to energy calculations, it was considered that the highest energy barrier of the reaction to yield N-substituted maleimide from MAN and primary amine presents in the first step by which N-substituted maleamic acid is produced. Formation of TBPMA is difficult because ΔΔG of TBPMA is about 2.6 times larger than that of PMA. These results seem to consistent with the above mentioned experimental findings, and orthophosphoric acid was found to be the effective catalyst for production of TBPMA and TBPMI. TBPMI as slight grayish white powder having mp of 142 °C was obtained by extraction of impurities with water and methanol, and its structure was confirmed by ¹H-NMR and IR spectroscopies.