An industrial applicable method for the synthesis of N‐alkylated maleimides based on fatty amines

A simple and economic two step synthesis of N‐alkylated maleimides with repeatable recycling of recovered starting materials from the second step is developed. In the first step, maleic anhydride is reacted with different natural mixtures of bio‐based fatty amines to give the corresponding maleic acid alkyl amides. The formation of the 5‐membered maleimide‐rings is achieved via acid‐catalyzed intramolecular condensation. However, in this step only 50–64% of the used alkyl amides are converted toward the required N‐alkylated maleimides. The novelty of our approach is the continuous recycling of recovered non‐converted amides for additional cyclization steps. These steps are repeated several times, whereby the yields of maleimides for each step leveled off at 46–50%. Practical Applications: Click reactions have become more and more prominent in the field of material science. A relevant used example is the [4 + 2]‐cycloaddition of maleimides and furans, whereby both moieties can be attached to the polymer backbone. This is a promising approach for the introduction of new functionalities to a polymer by a simple addition reaction. For this purpose a polymer, which contains furan groups and a functionalized maleimide are needed. For example, the use of fatty acid based maleimides allows the introduction of hydrophobic properties to a furan‐functionalized polymer, due to their long alkyl chain. However, the functional group of the maleimide can be varied to introduce other properties, like antimicrobial, hydrophilic or combinations thereof. This technique is interesting for coatings and allows the adaption of surface properties in a wide range. Moreover, maleimides can be used as polymerizable monomers to synthesize high performance macromolecular systems like polymers with high thermal stability