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Keywords:

  • alcohols;
  • N-alkylation;
  • hydrogen autotransfer;
  • iridium;
  • sulfonamides;
  • water-soluble catalyst

Abstract

Thumbnail image of graphical abstract

The water-soluble iridium complex {Cp*Ir[6,6′-(OH)2bpy](H2O)}[OTf]2 (Cp*=η5-pentamethylcyclopentadienyl, bpy=2,2′-bipyridine) was found to be a general and highly efficient catalyst for the N-alkylation of the poor nucleophilic sulfonamides with alcohols as alkylating agents in water. The presence of OH units in the bpy ligand is crucially important for the catalytic activity of the iridium complex. Mechanistic investigations revealed that the catalytically active species is a ligand-metal bifunctional iridium complex bearing an N,N′-chelated 2,2′-bipyridinated ligand and an aqua ligand. Notably, the present catalytic system and the proposed mechanism provide a new horizon and scope for the development of “hydrogen autotransfer (or hydrogen-borrowing) processes”.