250
M. C. A. van Vliet et al.
LETTER
1H NMR (300 MHz; CDCl3) 1.26 (s, 3H); 1.31 (s, 3H); 1.5 (m, 4H);
2.12 (q, 2H, J = 7 Hz); 2.72 (t, 1H, J = 6 Hz); 5.0 (m, 2H); 5.8 (m,
1H).
Table 4 Uncatalysed epoxidations with 60% H2O2 in hexafluoro-
2-propanol
13C NMR (75 MHz; CDCl3) 18.4; 24.9; 25.8; 28.3; 33.5; 58.2; 64.3;
114.8; 138.4.
Acknowledgement
This research was sponsored by the Dutch Innovation Oriented Re-
search Program on Catalysis (IOP Catalysis, IKA 96018).
References and Notes
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Conditions: Alkene, 1 M in hexafluoro-2-propanol with 2 eq. 60%
H2O2 and 0.05 eq. Na2HPO4. Stirring at room temperature. Analysis
by GLC. a Isolated yield on 5 mmol scale 81%. b Reflux under N2.
The less reactive terminal alkenes could be epoxidised in
moderate conversion by using boiling hexafluoro-2-pro-
panol.
A plausible explanation for the remarkable rate-enhanc-
ing effect of perfluorinated alcohols is based on their
unique property of donating hydrogen bonds (e.g. to
H2O2) without acting as a hydrogen bond acceptor. The
electron density on the O-O bond of hydrogen peroxide is
thereby decreased, as was demonstrated using NMR
techniques13, causing an increase in reactivity in electro-
philic epoxidation.
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In conclusion, the combination of fluorinated alcohol sol-
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synthetic methodology for relatively reactive alkenes,
such as various terpenes.
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General Procedure
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(14) Selectivity is, in this paper, defined as moles of epoxide
produced per mol of converted alkene. Amounts of epoxide
and remaining alkene were determined by calibrated GLC,
using an internal standard technique with predetermined
response factors.
2,3-Epoxy-2-methyl-7-octene by epoxidation in refluxing triflu-
oroethanol
2-Methyl-2,7-octadiene (1.24 g; 10 mmol), disodium hydrogen-
phosphate (71 mg; 0.5 mmol), trifluoroethanol (10 ml) and hydro-
gen peroxide (1 ml; 60%; 20 mmol) were heated under reflux under
a nitrogen atmosphere for 4 h. After cooling, the mixture was dilut-
ed with diethyl ether (50 ml). The organic phase was washed with
water (25 ml), aqueous sodium bisulphite (1 M; 25 ml) and concd
NaCl-solution (25 ml). The aqueous layers were extracted with an
additional amount of diethyl ether. The combined organic phases
were dried over Na2SO4 and evaporated under reduced pressure.
The residue (1.3 g) was distilled on a Kugelrohr apparatus. The
epoxide was obtained as a colourless oil (0.96 g; 6.9 mmol; 69%).
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GLC: >99% purity.
GLC-MS: 140 (M+).
Article Identifier:
1437-2096,E;2001,0,02,0248,0250,ftx,en;L18600ST.pdf
Synlett 2001, No. 2, 248–250 ISSN 0936-5214 © Thieme Stuttgart · New York