What are the reaction pathways of arylamines with selenium dioxide (SeO₂) in acetonitrile?

The study investigates the detailed analysis of the reaction between arylamines (such as aniline, o-anisidine, and methyl anthranilate) with selenium dioxide (SeO₂) in acetonitrile. The reaction progress follows three major pathways: electrophilic selenation, oxidative polymerization, and solvent oxidation. The specific pathways depend on the substituents on the arylamine.

From: "Competing electrophilic substitution and oxidative polymerization of arylamines with selenium dioxide", Beilstein J. Org. Chem. 2024, 20, 1221–1235.

The reaction of arylamines with SeO₂ in acetonitrile leads to three major pathways:
Electrophilic Selenation: This pathway involves the formation of diaryl selenides. For methyl anthranilate, the selenation pathway was prominent due to the delocalization of the amine lone pair electrons over the adjacent carboxylate function.
Oxidative Polymerization: This pathway leads to the formation of polyaniline polymers. Aniline and o-anisidine predominantly underwent oxidative polymerization, forming polyaniline polymers as major products.
Solvent Oxidation: This pathway results in the formation of oxamides due to the oxidation of the solvent (acetonitrile).
Conclusion: The reaction pathways of arylamines with SeO₂ are influenced by the substituents on the arylamine. Electron-donating groups promote oxidative polymerization, while electron-withdrawing groups favor electrophilic selenation.