Communication
ChemComm
phase (Fig. S7, ESI†). The recycling of E after filtration showed The application of the molecular imprinting of a supported
similar epoxidation performances without significant loss of the metal complex would be promising to achieve ultimate selec-
activity (Table 1, entries 5 and 6; Table S5, ESI†). These results tivity for catalytic conversions of natural compounds with many
suggested the considerable stability of E under the oxidation functional groups to suppress unfavorable reactions of other
conditions.
The stacking manner of the SiO2-matrix overlayers seemed
oxidizable functional intramolecular groups.
This work was financially supported by the JSPS Funding
to be affected by the shape-selective manner on E, and we Program for Next-Generation World-Leading Researchers (GR090),
investigated the modification of the molecular imprinting condi- MEXT/JSPS KAKENHI Grants No. 23750068, 26620043, and
tions, e.g. the temperatures of the hydrolysis–polymerization and JP16H06512 (Coordination Asymmetry) in Japan, the MEXT project
the addition of basic silane-coupling reagents to promote the of Integrated Research on Chemical Synthesis, the Kao Foundation
polymerization of TMOS.15 However, decreasing the temperatures for Arts and Sciences, and the Noguchi Institute. XAFS measure-
of the hydrolysis–polymerization significantly decreased the ments were performed with the approval of PF-PAC (No.
C5QC6 chemoselectivity without the improvement of the 2014G059 and 2014G060). XPS measurements were conducted
b-epoxide stereoselectivity, and the addition of basic promoters at Nagoya University Nanofabrication Platform, supported by the
(3–7, ESI†) decreased the oxidation activity and did not improve ‘‘Nanotechnology Platform Program’’ of MEXT, Japan.
the b stereoselectivity (Table S4, ESI†).
We also investigated the potential chemoselectivity of the
C5QC6 epoxidation of other cholesterol derivatives on E. The
Conflicts of interest
oxidation of pregnenolone and dehydroepiandrosterone, which
are smaller than cholesterol, was smoothly completed on E,
and the C5QC6 epoxide yields were 81 and 73%, respectively
(Table 1, entries 8 and 10), which were much higher than those
on B without the molecular imprinting. Comparable C5QC6
epoxide yield (76%, Table 1, entry 12) was also observed for the
oxidation of methylandrostenediol with two OH groups at the
3- and 17-positions. Decomposition of the epoxide products of
pregnenolone, dehydroepiandrosterone, methylandrostenediol,
and 16-dehydropregnenolone was found during chromatography
separation to correct isolated products.
There are no conflicts to declare.
Notes and references
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Chem. Commun.
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