Sonochemical formation of iodohydrin and epoxide from cyclohexene

Article abstract of DOI:10.1080/00397910701226467

Ultrasonic irradiation substantially improves the reaction of cyclohexene with I2 in aqueous dioxane in the presence of Cu(OAc)2 · H2O to generate the expected iodohydrin in high yield. The product undergoes cyclization to the epoxide by biphasic treatment with either Na2CO3 or KOH in a sonication-sensitive step. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910701226467

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Sonochemical Formation of Iodohydrin and
Epoxide from Cyclohexene
a
a
a
Vanessa S. Fernandes , Jayne C. S. Barboza, & Antônio Aarão Serra
a
Department of Chemical Engineering, Fine Chemistry Laboratory,
Faculdade de Engenharia Química de Lorena, Faenquil, Lorena, Brazil
Available online: 11 May 2007
To cite this article: Vanessa S. Fernandes, Jayne C. S. Barboza, & Antônio Aarão Serra (2007): Sonochemical
Formation of Iodohydrin and Epoxide from Cyclohexene, Synthetic Communications: An International Journal
for Rapid Communication of Synthetic Organic Chemistry, 37:9, 1433-1436
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Synthetic Communications , 37: 1433–1436, 2007
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910701226467
Sonochemical Formation of Iodohydrin and
Epoxide from Cyclohexene
Vanessa S. Fernandes, Jayne C. S. Barboza, and
Ant oˆ nio Aar a˜ o Serra
Department of Chemical Engineering, Fine Chemistry Laboratory,
Faculdade de Engenharia Qu ´ı mica de Lorena, Faenquil, Lorena, Brazil
Abstract: Ultrasonic irradiation substantially improves the reaction of cyclohexene
.
with I
expected iodohydrin in high yield. The product undergoes cyclization to the epoxide
by biphasic treatment with either Na CO or KOH in a sonication-sensitive step.
2
in aqueous dioxane in the presence of Cu(OAc) H O to generate the
2
2
2
3
Keywords: Epoxidation, iodohydrin, ultrasonic irradiation
INTRODUCTION
Halohydrins and epoxides are important intermediates in organic synthesis,
and many methods are available for their preparations.
[1–3]
The two
families of compounds are closely interconnected (i.e., one can be obtained
from the other by ring closure or opening). Thus the oxidation of an olefin
to the halohydrin followed by cyclization with base yields the epoxide; on
the other hand, halohydrins can be prepared, inter alia, from cyclohexene by
[4]
using a tin(II) halide–catalyzed process under sonochemical activation.
Thus, studies aimed at an improved access to one of the functionalities can
have double effects. We have chosen to study the effect of ultrasounic
[
5]
irradiation on the copper-mediated reaction of iodine with cyclohexene as
a typical model (Scheme 1). Significant results are reported in this note.
Received in the USA October 2, 2006
Address correspondence to Jayne C. S. Barboza, Department of Chemical Engineer-
ing, Fine Chemistry Laboratory, Faculdade de Engenharia Qu ´ı mica de Lorena,
Faenquil, 12600-970 Lorena, SP, Brazil. E-mail: jayne@dequi.faenquil.br
1
433

1
434
V. S. Fernandes, J. C. S. Barboza, and A. A. Serra
Scheme 1.
METHODS AND RESULTS
The purity of homemade cyclohexene (from cyclohexanol) was checked
1
13
by usual methods (gas chromatography, H and C NMR, IR spectra).
Cyclohexene preparation: cyclohexanol was added to phosphoric acid
(
85 wt.%), and cyclohexene was distilled off at 60–808C. The product
[1]
was redistilled at 748C. Literature conditions were applied to prepare
standard samples of 1-iodo-2-hexanol 2. Cyclohexene oxide and n-octane
(
Aldrich) were used as the standard and internal standard respectively.
Temperature was kept in the range of 23–258C. GC analyses were
performed on a CP3380 Varian gas chromatograph with FID using a CP-
Sil 8 CD (silica capillary column, 30 m long, 0.32 mm ID, and 0.25 mm
phase thickness, CP 8752) with N2 as carrier gas. Oven temperature,
2
1
.
initially at 508C (5 min), rose to 1108C at a rate of 208C min and was
kept constant at the final value for 8 min. The injector and detector temp-
1
13
eratures were 2308C and 2608C, respectively. H NMR and C NMR
were obtained on a Mercury 300-MHz and Varian spectrometers in
CDCl3 solutions with tetramethylsilane as internal standard. IR spectra
were recorded on a Perkin-Elmer FT-IR Spectrum One.
A 50-mL Erlenmeyer flask was loaded with cyclohexene 1 (0.21 g,
.
2
.60 mmol), Cu (OAc)2 2H O (0.259 g, 1.30 mmol), n-octane 99 þ %
2
(
water (0.8 mL) (dioxane–H O ratio 7:1) . The flask was closed with a
0.31 g, 2.71 mmol), iodine (0.493 g, 1.95 mmol), dioxane (5.6 mL), and
[1]
2
rubber septum, and the heterogeneous mixture was sonicated in a laboratory
cleaner (Kerry Pulsatron 60, 38 kHz) thermostated by running cold water in
a steel coil placed inside the bath. Reaction temperature was 23–258C.
Samples (0.2 mL) were collected at the specified time, and solid materials
w
were filtered off through Celite . CH Cl (3 mL) was added, and the
2
2
resulting solution was treated with 2 mL of NaBH in ethanolic suspension
4
(1% w/v). The solutions were washed three times with water, and all the
organic fractions were dried over anhydrous Na SO followed by filtration
through a cotton plug before GC analysis (0.1 mL). A purified sample 2
2
4
1
gave the following data: H NMR: d 4.12–3.95 (m, 1 H), 3.72–3.58 (m, 1
H), 2.55–2.40 (m, 1 H), 2.16–1.94 (m, 2 H), 1.92–1.78 (m, 1 H), 1.58–
1
.45 (m, 1 H), 1.44–1.15 (m, 4 H) ppm. C NMR: d 76.1, 43.0, 38.5, 33.5,
3
1
2
6
8.0, 24.2 ppm. IR: n 3384, 2933, 2856, 1447, 1161, 1033, 952, 858,
2
1
57 cm
.

Iodohydrin and Epoxide from Cyclohexene
1435
Cyclization to cyclohexene oxide 3 was effected in a similar manner. A
0-mL Erlenmeyer flask was loaded with iodohydrin (0.34 g, 1.50 mmol),
Na CO (0.22 g, 2.10 mmol), water (5.6 mL), and C H OH (1.4 mL), with
5
2
3
2 5
decane (0.079 g) as an internal standard. The flask was closed with a rubber
septum and sonicated for 60 min at 23–258C. Samples (0.1 mL) were
collected at 15-min intervals and diluted with CH Cl (2 mL); the organic
2
2
phase was washed with water (3x), dried (anhydrous Na SO ), filtered
2
4
through a cotton plug, and analyzed by GC (0.1 mL).
Alternatively, using potassium hydroxide (0.062 g, 1.10 mmol), the
mixture of iodohydrin (0.20 g, 0.90 mmol), water (1.6 mL), pentane (2.6 mL),
and Et O (2.6 mL) in a 50-mL Erlenmeyer flask, with decane (0.062 g) as an
2
internal standard, was sonicated for 40 min at 23–258C. Samples (0.1 mL)
were collected at intervals of 10 min and worked up as before, prior to GC
analysis. Spectra of purified samples agree with published data.
From the results summarized in Tables 1 and 2, the sonication-induced
acceleration of both process appears clearly. Higher yields were obtained
.
using equimolar amounts of Cu(OAc)2 2H O, in contrast with the twofold
2
excess required in published procedures (Table 1). Amounts lower than stoi-
chiometrc give poor results, as normally expected because the copper salt acts
as a source of acetate ions. The effect of the water percentage was considered
in a second step, as shown in Table 2. Even when the amount of the organic
phase decreased (different ratios of dioxane and water), good results were still
achieved (Table 2).
Alkaline treatment of 2 produced cyclohexene oxide 3 with 70% yield
within 60 min in a sonication step (59%, 24 h, different systems, under
[
2]
agitation ) when Na CO was used and 100% (40 min) with KOH (83%,
2
3
[1]
0 min ).
5
Table 1. Reaction yields for the sonochemical and conventional sys-
tems to generate iodohydrin
Yield (%) sonication
Yield (%)
a
b
c
.
.
2H
Time (h)
agitation
Cu(OAc)
2
2H
2
O
Cu(OAc)
2
2
O
0
1
1
2
2
3
1
.5
.0
.5
.0
.5
.0
8
7.8
24.0
29.5
34.8
45.0
48.0
36.3
66.5
76.2
79.2
83.5
86.7
89.0
a
[1]
Conditions reported in literature
.
:
Ratio of alkene to
Cu(OAc)
b
2
2H
Sonochemical reaction with. ratio alkene to Cu(OAc)2 2H O: 2 to 1.
2
O: 2 to 1.
.
2
c
.
2 2
2H O: 1 to 1.
Ratio of alkene to Cu(OAc)

1
436
V. S. Fernandes, J. C. S. Barboza, and A. A. Serra
Table 2. Influence of solvent composition on the sonochemical
reaction yields (%) of the iodohydrin
Dioxane–
a,b
water (7:1)
Dioxane–
b
water (1:1)
Dioxane–
b
water (1:3)
Time (h)
0
1
1
2
2
.5
.0
.5
.0
.5
36.3
66.5
76.2
79.2
83.5
42.9
62.0
64.4
68.5
60.0
10.3
20.2
21.0
26.0
39.4
a
Sonochemical formation of iodohydrin with solvent conditions
reported in literature
[1].
b
.
2 2
2H O: 1 to 1.
Ratio alkene to Cu(OAc)
This procedure proves to be convenient for the synthesis of iodohydrin
and epoxide from cyclohexene under ultrasound irradiation. Extension to
various classes of olefins, now under study, will determine the application
of the procedure.
ACKNOWLEDGMENTS
Financial support by the Funda c¸ a˜ o de Amparo a` Pesquisa do Estado de S a˜ o
Paulo (FAPESP) and Conselho Nacional de Desenvolvimento Cient ´ı ficoe
Tecnol o´ gico (CNPq) is greatly acknowledged. Thanks are also due to H. F.
de Castro (Department of Chemical Engineering/Faculdade de Engenhoria
Qu ´ı mica de Lorena (DEQUI/FAENQUIL)) and J.-L. Luche (France) for
fruitful discussions.
REFERENCES
1
2
3
. Sanseverino, A. M.; Mattos, M. C. S. Synthetic Commun. 1998, 28, 559, and refer-
ences cited.
. Sanseverino, A. M.; Silva, F. M.; Jones, J., Jr.; Mattos, M. C. S. J. Braz. Chem. Soc.
2
000, 11, 381, and references cited.
. Marco-Contelles, J.; Molina, M. T.; Anjum, S. Chem. Rev. 2004, 104, 2857, and
references cited.
4
5
. Luche, J.-L.; Einhorn, C. J. Chem. Soc., Chem. Commun. 1986 1368.
. Luche, J.-L. Synthetic Organic Sonochemistry; Plenum Press: New York, 1998.