Sequential reaction of p-toluidine with 2,3-dichloromaleic anhydride: Synthesis and molecular structure of 2-chloro-3-p-toluidino-N-p-tolylmaleimide

Abstract

The reaction of equimolar amounts of p-toluidine with 2,3-dichloromaleic anhydride in refluxing toluene affords 2,3-dichloro-N-p-tolylmaleimide (1) and 2-chloro-3-p-toluidino-N-p-tolylmaleimide (2), as the major and minor products, respectively. While increasing the amount of p-toluidine relative to 2,3-dichloromaleic anhydride yields the latter compound as the major product, the replacement of the chloro group in 2-chloro-3-p-toluidino-N-p-tolylmaleimide by added p-toluidine was not observed in refluxing toluene. Both 1 and 2 were isolated by column chromatography and characterized in solution by IR and NMR spectroscopies. The solid-state structure of 2-chloro-3-p-toluidino-N-p-tolylmaleimide was solved by X-ray crystallography. Further, 2-Chloro-3-p-toluidino-N-p-tolylmaleimide crystallizes in the monoclinic space group C2/c, a = 33.191(8) Å, b = 4.037(1) Å, c = 24.876(6) Å, β = 107.050(4)°, V = 3187(1) ų, Z = 8, and d _calc = 1.362 mg/m³; R = 0.0561, R _w = 0.1246 for 2087 reflections with I > 2σ (I).