Imidazole als Induktoren der Cyclo‐Oligomerisation von N‐Alkyl‐maleinimiden und der cis‐trans, Umlagerung von Maleinsäure‐dimethylester

N-Methylimidazole (N–M), in boiling acetonitrile, catalyzes the oligomerization of N-alkyl maleimides (2) to tri-, tetra-, penta- and hexamers. In the presence of small amounts of hydroquinone the trimers of 2 are formed, which have the structure of N,N′,N″-trialkyl-cyclohexane-1,2,3,4,5,6-hexacarboxy-1,2:3,4:5,6-tri-midies (6). A possible mechanism of this catalytic cyclo-oligometization is discussed. Dependant from the chemical nature of the N-alkyl substituent of the maleimides, imidazole or benzimidazole and some of its C-substituted products also can function as oligomerization catalysts. However in this case the normal 1:1 addition is the main reaction, as observed also with pyrazoles plus 2. Maleic dimethylester was isomerized to fumaric dimethylester in the presence of N-methylimidazol. These observations reveal additional catalytic functions to the well known hydrolysis catalyzing properties of imidazoles.