SYNTHESIS OF N-(2,4,6-TRIBROMOPHENYL)MALE IMIDE

Synthesis of N-(2,4,6-tribromophenyl) maleimide (TBPMI) from maleic an hydride (MAN) and 2,4,6-tribromoaniline (TEA) was investigated. Althou gh N-phenylmaleamic acid (PMA) is really prepared by the reaction of a niline (ANL) and MAN, N- (2,4, 6-tribromophenyl) maleamic acid (TBPMA) was not obtained by attempted reaction of TEA with MAN even at higher temperature. N-Phenylmaleimide (PMI) is produced with a high yield us ing orthophosphoric acid as catalyst. Unlikely TBPMI was synthesized w ith only a low yield under similar conditions. However, it was found t hat TBPMI can be prepared with a high yield in mesitylene under reflux conditions at 168 degrees 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 firs t step by which N-substituted maleamic acid is produced. Formation of TBPMA is difficult because Delta Delta G of TBPMA is about 2.6 times l arger than that of PMA. These results seem to consistent with the abov e 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 degrees C was obtained by extraction of impurities with water and methanol, and its structur e was confirmed by H-1-NMR and IR spectroscopies.