Fluorocarbon Soluble Copper(II) Carboxylate Complexes with Nonfluoroponytailed Nitrogen Ligands as Precatalysts for the Oxidation of Alkenols and Alcohols under Fluorous Biphasic or Thermomorphic Modes:Structural and Mechanistic Aspects

摘要

This fluorous biphasic catalysis (FBC) contribution was focused on the synthesis and characterization of new fluorous soluble Rf-Cu(II) carboxylate complexes containing nonfluoroponytailed ligands and defines their role as precatalysts for the FBC oxidation of alkenols and alcohols in the presence of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO)/O_2.In this FBC approach,we have utilized the phase-switching technique of Vincent et al.(J.Am.Chem.Soc.2002,124,12942) to solubilize the nonfluoroponytailed ligands,N-1,4,7-Me_3TACN,2,and N-1,4,7-pentamethyldiethylene-triamine (PMDETA),3,by reaction with a fluorous solvent-soluble copper (II) dimeric complex,[Cu({C_8F_(17)(CH_2)_2}_2-CHCO_2)_2]_2,1.Moreover,the reaction of nonfluoroponytailed ligands 2 and 3 with 1 afforded new perfluoroheptane-soluble Cu(II) complexes,[Cu({C_8F_(17)(CH_2)_2}_2CHCO_2)_2(2)],4,and [Cu({C_8F_(17)(CH_2)_2}_2CHCO_2)_2 (3)],5,respectively.The known Cu(II) complex,1,was further characterized by electron paramagnetic resonance (EPR) spectroscopy confirming its dimeric structure,while 4 and 5 were characterized by elemental analysis,IR,diffuse reflectance UV-vis,and EPR spectroscopy.Furthermore,1,4,and 5 were evaluated as precatalysts for alkenol and alcohol oxidation.The oxidation reactions of alkenols and alcohols in the presence of TEMPO/O_2 proceeded under FBC conditions for 1,4,and 5,but 1-octanol was unreactive under single-phase FBC conditions at 90 deg C with TEMPO/ O_2.The thermomorphic property of 5,soluble in chlorobenzene/toluene at 90 deg C but insoluble at room temperature,was also evaluated in the selective oxidation of p-nitrobenzyl alcohol to p-nitrobenzaldehyde.Plausible mechanisms concerning these FBC/thermomorphic oxidation reactions will be discussed.