Synthesis of Pharmacologically Relevant New Derivatives of Maleimides via Ligand-Free Pd-Catalyzed Suzuki–Miyaura Cross-Coupling Reactions

The Suzuki–Miyaura coupling reactions were applied for synthesis of pharmacological relevant derivatives of known 3,4-dibromo-1-methyl-1H-pyrrole-2,5-dione compound. Suzuki–Miyaura reactions of 3,4-dibromo-1-methyl-1H-pyrrole-2,5-dione with two equivalents of arylboronic acids gave vicinal diphenyl-substituted maleimide products. The reaction with one equivalent of arylboronic acid resulted in site-selective synthesis of N-methyl-2-aryl-3-bromomaleimide. The one-pot reaction of 3,4-dibromo-1-methyl-1H-pyrrole-2,5-dione with two different arylboronic acids afforded N-methyl-2-3-diaryl-maleimides containing two different aryl groups. Maleimide-resulting compounds have added a general interest in the fields of Pharmaceuticals, diagnostics, materials and catalysis. The synthesis of maleimide-substituted compounds via Suzuki–Miyaura cross-coupling protocols has increased extensive interest in the synthesis of heterocyclic compounds.