Unexpected chlorine substitution by hydrogen in the reaction of 2-chloro-3-p-toluidino-N-p-tolylmaleimide with DBU: Synthesis and molecular structure of 2-p-toluidino-N-p-tolylmaleimide
作者:William H. Watson、Guanmin Wu、Michael G. Richmond
DOI:10.1023/b:jocc.0000044091.78129.37
日期:2004.9
The reaction of p-toluidine with 2,3-dichloromaleic anhydride in the presence of added 1,8-diazabicyclo[5.4.0] undec-7-ene (DBU) does not give the known compound 2-chloro-3- p-toluidino-N-p-tolylmaleimide (1), but rather 2-p-toluidino-N-p-tolylmaleimide (2) in low yields. Repeating this same reaction with Et3N, pyridine, tmeda, and 4-Me(2)Npyridine in place of DBU furnishes the expected product 2-chloro-3-p-toluidino-N-p-tolylmaleimide, without the presence of 2-p-toluidino-N-p-tolylmaleimide. The participation of DBU in the chlorine for hydrogen exchange reaction in compound 1 has been demonstrated from the independent thermolysis reaction of 1 with DBU in toluene, where 2 was obtained as the sole isolable product. Compound 2 was isolated and fully characterized in solution, and the molecular structure was established by X-ray diffraction analysis. 2-p-Toluidino-N-p-tolylmaleimide crystallizes in the monoclinic space C2/c, a = 33.630( 5), b = 12.508( 2), c = 7.381( 1), beta = 90.668( 3), V = 3104.3( 8)(3), Z = 8, and D-calc = 1.251 Mg/m(3); R = 0.0357, R-w = 0.0896 for 2011 reflections with I > 2sigma(I).