Bipyridine copper functionalized polymer resins as support materials for the aerobic oxidation of alcohols

Abstract

Here, we report the first polymer resin supported Cu(I)/bipyridine/N-oxyl catalyst systems for the aerobic oxidation of alcohols at room temperature with ambient air. We chose polystyrene-poly(ethylene glycol) copolymer (TentaGel ® ) and Merrifield resin as support materials because of their different swelling properties in polar and nonpolar solvents. The bromo functionalized TentaGel resin TG1 or Merrifield resin MR1 were functionalized with 4,4 ′ -dimethoxy-2,2 ′ -bipyridine ( MeO bpy) to give the ligand modified polymer resin TG2/MR2 that was loaded with Cu I (Br) to give the final Cu I (Br)/bipyridine support TG3/MR3. These resins were characterized by Fourier transform infrared, SEM, SEM energy dispersive X-ray spectroscopy and elemental analysis. Catalytic activity and recyclability of TG3 was investigated in acetonitrile and cyclohexane and displayed high activities in acetonitrile but also high metal leaching. In cyclohexane as solvent leaching was reduced to 1% − 2%, and catalytic activity was still at 75% after the fifth run. MR3 was consequently tested in cyclohexane and toluene. In both solvents low metal leaching was observed with higher activity in toluene as solvent, showing still over 90% conversion after the seventh run with 9-azabicyclo[3.3.1]nonane N-oxyl (ABNO) and 80% with 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO).

A Resin‐Bound Peptoid as a Recyclable Heterogeneous Catalyst for Oxidation Reactions

“…In our previous work, BT and DI were synthesized on a Rink‐amide resin. However, literature reports both on solid‐supported CuBipy catalysts and on resin‐bound peptide catalysts, suggest that the use of TentaGel (polyethylene glycol–polystyrene) resin leads to the best catalytic results , . We therefore decided to prepare the two peptoids on TentaGel resin.…”

“…The functionalization of copper‐bipyridine (CuBipy) with polymer resins was already reported, showing that solid‐supported CuBipy can catalyze the aerobic oxidation of primary benzylic alcohols in a heterogeneous system . In this system, however, only Bipy was supported, while the nitroxyl catalyst operated in solution.…”

Functionalized Polyethylene Glycol as a Catalyst for Esterification of Salicylic Acid

“…Polymer-supported catalysts have the benefit of being able to manipulate their textural characteristics by changing the synthesis conditions. Furthermore, this type of material is less toxic in comparison with metal catalysts, as it is not susceptible to leaching [8][9][10]. Larger surface areas in porous polymer particles result in a greater number of catalytic sites, therefore controlling this characteristic as a function of polymerization factors is of significant importance [11].…”

Electrochemical Performance of ABNO for Oxidation of Secondary Alcohols in Acetonitrile Solution

“…Recently, a stable nitroxyl radical 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) has been successfully applied to synthesize aldehydes, nitriles, and imines because of its cleaness and inexpensiveness [14,15,16]. Several combinations of TEMPO and transition metals, especially Fe and Cu, have been widely used for the synthesis of aldehydes from alcohols [17,18,19,20,21,22,23,24,25,26,27,28,29]. Despite of using molecular oxygen as the terminal oxidant, the transition-metal catalyst still exists in these processes.…”