Method of preparation of maleimides by thermal cyclization of maleamic acids in the presence of a catalyst

Abstract

Method of preparation of maleimides by thermal cyclization of maleamic acids in the presence of a catalyst consists in that reaction of a substituted maleic anhydride with a primary amine is performed in an organic solvent in the presence of betaine at a temperature of 100 to 180° C., at a ratio of the primary amine to the substituted maleic anhydride of 0.6:1.6. Maleimides, obtained in this way, are further purified by extraction, and finally, they are crystallized. As a catalyst, there may be also used betaine in a mixture with inorganic and organic acids, or betaine may be deposited on a solid carrier, or possibly, betaine may be deposited on a carrier in combination with inorganic acids.

Dependencies are inferred from the claim text.