Selective dehydrogenation (oxidation) of 3,4-dimethoxybenzyl alcohol by a non-heme iron lignin-peroxidase reaction mimic

Abstract

In pyridine, bis(2,2′-bipyridine)iron(II) (Fe(bpy) 2+ 2) activates hydrogen peroxide for the efficient and selective catalytic dehydrogenation (oxidation) of veratryl alcohol (model-substrate monomer for lignin; 3,4-(MeO) 2PhCH 2OH). Several other complexes (Fe II(OPPh 3) 2+ 4, Fe II(O 2bpy) 2+ 2, Fe II(MeCN) 2+ 4, Fe II(PA) 2, Fe IIICl 3) are effective catalysts for the dehydrogenation of veratryl alcohol and benzyl alcohol, but their selectivity (relative reactivity with 3,4-(MeO) 2PhCH 2OH vs. PhCH 2OH) is less than the 6.1 ratio that is observed for the optimized Fe II(bpy) 2+ 2/H 2O 2/pyridine(py) system. The reactivities have been determined for several other methoxybenzyl alcohols that are model substrates for lignin (e.g.,4-MeOPhCH 2OH and (MeO) 3PhCH 2OH).