10.1002/chem.201605661
Chemistry - A European Journal
FULL PAPER
was added to a solution of [P4,4,4,4]Br (0.589g,2 mmol) in dry ethanol (10
mL), and the mixture was stirred vigorously at 0 oC for 12 h. The
precipitated KCl and the excess of KOH were filtered off, This step could
be repeated until no chloride ions in the filtrate were detectable by a
silver nitrate test. Then the filtrate was evaporated and concentrated to 5
mL before use at 40 oC. The filtrate was stirred with an aqueous solution
of ammonium tetraperoxotantalate ((NH4)3[Ta(O2)4], 0.7 mmol) at 40 °C
for a few hours. When the reaction was finished, dichloromethane (20 ml)
was added to the solution. The product was extracted for three times.
The extract was dried with anhydrous magnesium sulfate and then
evaporated at 40 oC for 3 h to obtain a bright yellow liquid (Figure S1).
[P4,4,4,4]3[Ta(O)3(-O2)]: Yield 0.62 g, 90%; 1H NMR (400 MHz, [D6]DMSO,
25 oC, TMS) : δ 2.16 (m, 8H,CH2), 1.40 (m, 16H,CH2), 0.94 ppm (q,
3J(H,H) = 8.0 Hz, 12H,CH3); 31P NMR (300MHZ, CDCl3 ): δ 32.91ppm
(Figure S2); elemental analysis calcd (%) for (C16H36P)3TaO5: C 55.49, H
10.40, P 8. 95, Ta 17.44; Found: C 51.22, H 9.92, P 8.19, Ta 16.10;
HRMS (70 ev): m/z(%): 244.93 (50) [TaO2(O2)]−, 246.95 (40)
Acknowledgements
The authors are grateful for support from the National
NaturalScience Foundation of China (21373082) and innovation
Program of Shanghai Municipal Education Commission
(15ZZ031), and theFundamental Research Funds for the Central
Universities.
Keywords: peroxotantalate anion • ionic liquid • epoxidation •
allylic alcohols • hydrogen bond
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[TaO3(H2O)]-,
280.95
(40)
[TaO2(O2)(H2O)2]-,
505.19
(100)
[H(P4,4,4,4)TaO4]-, 521.18 (30) [H(P4,4,4,4)TaO3(O2)]-. Number of peroxide
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[P4,4,4,8]3[Ta(O)3(-O2)] was prepared by using [P4,4,4,8]Br as
a
starting material in a similar method. The resulting material was a yellow
viscous liquid (Figure S1). [P4,4,4,8]3[Ta(O)3(-O2)]: yield 0.77 g, 96.1%; 1H
NMR (400 MHz, [D6]DMSO, 25 oC, TMS): δ 2.17 (m, 8H, CH2), 1.27−1.43
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ppm (Figure S2); elemental analysis calcd (%) for (C20H44P)3TaO5: C
59.71, H 10.95, P 7.71, Ta 15.09; Found: C 55.25, H 10.14, P 7.15, Ta
13.98; HRMS (70 ev): m/z (%): 595.26 (20) [H(P4,4,4,8)TaO5(H2O)]-,
875.57 (100) [(P4,4,4,8)2TaO4]-. Number of peroxide bonds: 0.95.
[P4,4,4,14]3[Ta(O)3(-O2)] was prepared by using [P4,4,4,14]Cl as
a
starting material in a similar method. The resulting material was a yellow
viscous liquid (Figure S1). [P4,4,4,14]3[Ta(O)3(-O2)]: yield 0.94 g, 96.5%;
1HNMR (400 MHz, [D6]DMSO, 25 oC, TMS): δ 2.20 (m, 8H, CH2),
1.29−1.43 (m, 36H, CH2), 0.86 ppm (m, 12H, CH3); 31P NMR (300MHZ,
CDCl3, ): δ 32.84 ppm (Figure S2); elemental analysis calcd (%) for
(C26H56P)3TaO5: C 64.16, H 11.5, P 6.38, Ta 12.39; Found: C 61.24, H
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11.19,
P 6.21, Ta 12.01; HRMS (70 ev): m/z (%): 661.33 (100)
[H(P4,4,4,14)TaO3(O2)]-, 1043.75 (80) [(P4,4,4,14)2TaO4]-, 1059.74 (30)
[(P4,4,4,14)2TaO3(O2)]-. Number of peroxide bonds: 0.94.
Typical reaction procedure for the catalytic epoxidation of allylic
alcohol
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A typical method for the epoxidation of allylic alcohols was as follows. A
mixture of allylic alcohol (2 mmol), 30% aqueous H2O2 (2 mmol), and the
ILs catalysts (0.05 mmol) were placed in a 25 mL schlenk flask equipped
with a magnetic stirrer and then stirred at 0 °C for some time. When the
reaction was finished, the mixtures were extracted for three times with
diethyl ether. The resulting organic layer was dried with Na2SO4 and then
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vacuum and could be recycled by addition of fresh substrate.
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Reaction Kinetics
The reaction was periodically monitored by the GC. In a typical
kinetics experiment, the concentration of IL catalyst was constant (0.05
M). In order to examine the effect of substrate concentration on the rate
of epoxidation, the concentration of 3-methyl-2-buten-1-ol was varied
from 1.0 to 2.5 M, while the concentration of hydrogen peroxide was 2 M.
Similarly, the effect of hydrogen peroxide concentration on the rate of
epoxidation was investigated through adjusting the concentration of
hydrogen peroxide from 1.5 to 3.0 M, while the concentration of 3-methyl-
2-buten-1-ol was 2 M. The other reaction conditions have been given in
the Figure captions (Figure S5). Reaction rates (R0) for the kinetic studies
were determined from the slopes of reaction profiles ([substrate]0-
[substrate]t vs time) at low conversions (<15%) (initial rate method).
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8
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