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A. Aghmiz et al.
4-cyclohexenone or 1,2-diphenylethanone and the low stereoselectivity in the epoxidation
of (Z)-stilbene suggest that a radical mechanism is operating in these processes, as
proposed for Mn-salen catalytic systems [34, 35]. The presence of a radical scavenger
produced a decrease in the conversion. As for the epoxidation of cyclohexene derivatives,
the system containing the amine functionality 2a presents slightly higher conversions than
1a, containing imine. The dimeric catalysts 1b provided the best results, although the
increase in conversion using this catalyst was only 10%. In this case, there is a two-fold
concentration of Mn in solution compared to 1a or 2a, which would be the reason for the
increased activity if the active species was a monomer. Otherwise, the coordinative
saturation of 1a and 1b may account for these differences. The epoxidation of styrene and
stilbenes with these catalysts proceed at low conversions and selectivities.
Supplementary material
Supplementary Data containing IR spectra, examples of NMR spectra of catalytic experi-
ments and UV-visible spectra of 1a and PhIO are available.
Acknowledgments
We gratefully acknowledge the Generalitat de Catalunya (SGR116), the Ministerio de
Ciencia e Innovación (CTQ2010-16676 and Consolider Ingenio CSD2006-0003) and the
Ministerio de Asuntos Exteriores (Programa de Cooperación Internacional C030686-10)
for the financial support. Dr J. Castilla is acknowledged for providing some experimental
data.
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