A novel Fe(III) salt-catalyzed monoterpene aerobic oxidation in methyl alcohol

• We report a novel, clean and cheap oxidative process for terpenic ether synthesis.
• Fe(III) salt catalysts show higher activity than palladium salts reported in literature.
• Catalyst efficiency was demonstrated by high TON and TOF.
• Although homolytic, monoterpene oxidation was highly selective in methyl alcohol.

The Fe(III)-catalyzed aerobic oxidation of monoterpenes in CH3OH has been developed, in which simple Fe(III) salts are used as catalysts in the absence of stabilizing ligands. Remarkably, Fe(NO3)3 catalyst efficiently promotes the oxidation of monoterpenes under air or dioxygen. The highest TON and TOF reached 476 and 162 h− 1, respectively. In general, reactions with 1.0–9.0 mol% of catalyst reached high conversions (ca. 90–99%) and high oxidation products selectivity (ca. 80%). Notably, α-pinene and β-pinene were selectively oxidized into only allylic product, myrtenol methyl ether. The significant breakthroughs of this simple oxidative process are the use of inexpensive Fe(III) salts as catalysts and environmentally-friendly oxidants (air or dioxygen).

Proposed mechanism for Fe(III)-catalyzed oxidation of β-pinene to myrtenol methyl ether by dioxygenFigure optionsDownload as PowerPoint slide