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a
Table 3 Catalytic properties of different substrates with H
2
O
2
on TS-1
In summary, we conclude that a new intermediate (II) with
double hydrogen bonds is formed in a catalytic oxidation
system over titanosilicates by introducing a hydrogen bond
acceptor. The catalytic activity of titanosilicates is enhanced
significantly as a resulting of the new intermediate with sui-
table stability due to the new hydrogen bond formed. This
study demonstrates that utilization of hydrogen bond inter-
actions provides a method for achieving high catalytic effi-
ciency in catalytic oxidation reactions over titanosilicates. We
expect that the insight obtained in this study can be further
extended to make clear the solvent effects in titanosilicate
catalytic oxidation systems which have not been understood
Convention/% Selecitivity/% Utilization/%
MAT Alkene Oxide
No. Substrate
H
2
O
2
2 2
H O
1
2
3
4
5
6
7
8
Allyl chloride
0
1
0
1
0
1
93.0
93.8
24.3
31.0
31.7
44.0
65.0
86.4
99.0 92.7
99.8 95.4
30.2 71.4
39.5 94.6
32.2 84.6
45.5 95.7
93.9
94.0
80.5
78.5
98.4
96.7
—
1-Octene
1-Heptene
Cyclopentene 0
1
—
—
8.74
90.3
—
a
Reaction conditions: substrate 10 mmol, for others see Fig. 1.
1
0,13,24
completely to date.
TS-1 are studied in Table 3. The desired results showed that not
only the selectivity of the epoxide product increased but also
the obvious enhancement in conversion of alkene was obtained
in favor of the hydrogen-bond interactions.
Based on the specific effect of hydrogen bond acceptors
on catalytic oxidation over TS-1, they can also be applied on
We gratefully acknowledge the National Natural Science
Foundation of China (20973064), the Science and Technology
Commission of Shanghai Municipality (12JC1403600), and the
Shanghai Leading Academic Discipline Project (B409).
Ti-MWW. Table S1 (ESI†) displays the effect of appropriate Notes and references
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3
1
2
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2
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1
3,24
zeolite,
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1
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À1
1
9.9 kJ mol , much lower than that without NH
3
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À1
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2
a
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the acceptor (e.g. NH ) when the hydrogen bond acceptor (e.g.
3
2
2
3
NH ) was introduced into the titanosilicate catalytic oxidation
system. That is the intrinsic reason for obvious catalytic epox-
idation enhancement of titanosilicates.
7
506 Chem. Commun., 2013, 49, 7504--7506
This journal is c The Royal Society of Chemistry 2013