Oxidation of 1,2,4-trimethylbenzene (TMB), 2,3,6-trimethylphenol (TMP) and 2-methylnaphthalene to 2,3,5-trimethylbenzoquinone (TMBQ) and menadione (vitamin K3)

Recent advances in transition-metal-catalyzed selective oxidation of substituted phenols and methoxyarenes with environmentally benign oxidants

“…The group of Beller have synthesized a range of Ru(II) complexes with tridentate nitrogen ligands and investigated their catalytic performances in the selective oxidation of various arenes [32,126,127]. Ruthenium(2,2',6':2''-terpyridine)(2,6-pyridinedicarboxylate) ([Ru(tpy)(pydic)], see Figure 4 for the structure) was identified as one of the most effective catalysts [127].…”

“…Hexacyanoferrate-catalyzed oxidation of trimethoxybenzenes delivered dimethoxy-p-benzoquinones[123]. For example, 1,3,5-trimethoxybenzene was oxidized to 2,6-dimethoxy-p-benzoquinone (Scheme 16).Beller and co-workers evaluated different iron complexes in the oxidation of a range of methylated phenols and naphthols using 30% H 2 O 2[32,124]. The best results were obtained with a three component system consisting of FeCl 3 ·6H 2 O, pyridine-2,6-dicarboxylic acid (H 2 Pydic) and n-butylbenzylamine (Scheme 17).…”

Aerobic Water–based Oxidation of 2,3,6‐Trimethylphenol to Trimethyl‐1,4‐benzoquinone over Copper(II) Nitrate Catalyst

“…As an alternative solution to these problems, various studies carry out the reactions in organic solvents, and the toxic metal oxides are replaced with some environmentally friendly oxidants, such as hydrogen peroxide or peroxyacids. Several catalysts like copper complex, iron complex, titaniumsilicates, cobalt complex, and heteropolyoxometalates indicate promising activities in these processes. However, the relative high cost of peroxides is a problem in application.…”

Oxidation

“…If a catalyst is easily recyclable, having to use high concentrations is not a real drawback. Unfortunately, this fact has not yet been widely recognized in academia, not even in very recent reviews [158].…”