Pd(II)催化亚胺的分子内磺酰胺化/氧化反应:便捷的合成1,2-双取代苯并咪唑化合物

1, 2-Disubstituted multifunctional benzimidazoles are an important class of heterocyclic building blocks which are found in various biologically active compounds. Up to now, many novel benzimidazole synthetic methods which involved transition metal-catalyzed intramolecular aryl guanidinylation or intermolecular cascade aryl amination/condensation, were reported successively, but the drawback of the above-mentioned approaches is the limited diversity of the substituent group at the 2-position of benzimidazole. In this paper the effects of imine substrate, transition metal salts, solvents, oxidants and reaction temperature etc. on the sulfonamidation/oxidation of imines were systematically investigated. Pd(II) chloride /(diacetoxyiodo) benzene-catalyzed reaction system could efficently realized intramolecular sulfonamidation/oxidation of O-sulfonamidophenyl imine to produce 1, 2-disubstituted benzimidazole in good to excellent yields under mild conditions. The substituent scope at the 2-position of benzimidazole can be extended to the alkyl, aryl, alkenyl, acyl, and esteryl functional group under mild conditions.