Epoxidation of strained alkenes catalysed by (1,2-dimethyl-4(1H)pyridinone-3-olate)2MnIIICl

• (1,2-Dimethyl-3-hydroxy-4(1H)pyridinone)2MnCl + co-catalyst + oxidant as epoxidation catalyst.
• Strained alkenes epoxidised with H2O2 or monoperoxysulfate.
• Co-catalyst include imidazole or sodium acetate.
• Mn(V) = O is proposed to be the active species (based on mass spectrometry study).

The mild epoxidation of strained alkenes using (DMPO)2MnCl catalyst (DMPO = 1,2-dimethyl-4(1H)-pyridinone-3-olate) in the presence of various oxidants was studied. Hydrogen peroxide and monopersulfate were found to be the best oxidants when used with imidazole in acetonitrile at 4 °C, with up to 94% conversion. Dismutation of hydrogen peroxide was also observed when used as an oxidant. The epoxidation using hydrogen peroxide or monoperoxysulfate appears to be mild and very selective for strained alkenes. A mechanism is proposed where imidazole is required for activation of the oxidant and where a detected MnV = O species is proposed as the active species. Competitive reaction between H2O2 and the substrate for the active species is proposed and homolytic vs heterolytic scissions of the OO bond of the oxidant are discussed.

Figure optionsDownload high-quality image (107 K)Download as PowerPoint slide