Green alkoxyiodination of cyclohexene mediated by natural clay

Article abstract of DOI:10.1081/SCC-200061577

The reaction of cyclohexene with iodine and alcohols (ethanol, isopropanol, and t-butanol) at room temperature is effectively mediated by clays to produce the corresponding trans-β-alkoxy-iodocyclohexane. Copyright Taylor & Francis, Inc.

Full text of DOI:10.1081/SCC-200061577

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Green Alkoxyiodination of
Cyclohexene Mediated by
Natural Clay
Raul A.S. Villegas a , José Luiz do Espírito Santo Jr. b
, Antonio M. Sanseverino a , Marcio C.S. de Mattos a
, Mônica R.M.P. de Aguiar b & Alcides W.S. Guarino c
a Departamento de Química Orgânica , Instituto de
Química, Universidade Federal do Rio de Janeiro ,
Rio de Janeiro, Brazil
b Departamento de Química Orgânica , Instituto de
Química, Universidade do Estado do Rio de Janeiro ,
Rio de Janeiro, Brazil
c Departamento de Ciências Naturais, Escola de
Ciências Biológicas , Universidade Federal do Estado
do Rio de Janeiro , Rio de Janeiro, Brazil
Published online: 16 Aug 2006.
To cite this article: Raul A.S. Villegas , José Luiz do Espírito Santo Jr. , Antonio M.
Sanseverino , Marcio C.S. de Mattos , Mônica R.M.P. de Aguiar & Alcides W.S. Guarino
(2005) Green Alkoxyiodination of Cyclohexene Mediated by Natural Clay, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 35:12, 1627-1631, DOI: 10.1081/SCC-200061577
To link to this article: http://dx.doi.org/10.1081/SCC-200061577
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Synthetic Communicationsw, 35: 1627–1631, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200061577
Green Alkoxyiodination of Cyclohexene
Mediated by Natural Clay
Raul A. S. Villegas
´ ˆ
Departamento de Quımica Organica, Instituto de Quımica, Universidade
´
Federal do Rio de Janeiro, Rio de Janeiro, Brazil
´
´
Jose Luiz do Espırito Santo, Jr.
´ ˆ ´
Departamento de Quımica Organica, Instituto de Quımica, Universidade
do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
Antonio M. Sanseverino and Marcio C. S. de Mattos
´
´ ˆ
Departamento de Quımica Organica, Instituto de Quımica, Universidade
Federal do Rio de Janeiro, Rio de Janeiro, Brazil
ˆ
Monica R. M. P. de Aguiar
´ ˆ ´
Departamento de Quımica Organica, Instituto de Quımica, Universidade
do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
Alcides W. S. Guarino
ˆ ˆ
Departamento de Ciencias Naturais, Escola de Ciencias Biologicas,
´
Universidade Federal do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
Abstract: The reaction of cyclohexene with iodine and alcohols (ethanol, isopropanol,
and t-butanol) at room temperature is effectively mediated by clays to produce the
corresponding trans-b-alkoxy-iodocyclohexane.
Keywords: Clay, coiodination, green chemistry
Received in the USA February 6, 2005
Address correspondence to Marcio C. S. de Mattos, Departamento de Quımica
ˆ ´
Organica, Instituto de Quımica, Universidade Federal do Rio de Janeiro, Caixa
´
ˆ
Postal 68545, CEP 21945-970, Rio de Janeiro, Brazil and Monica R. M. P. de
´
ˆ
´
Aguiar, Departamento de Quımica Organica, Instituto de Quımica, Universidade do
Estado do Rio de Janeiro, CEP 20550-013, Rio de Janeiro, Brazil. E-mail:
mmattos@iq.ufrj.br and mmarques@uerj.br
1627

1628
R. A. S. Villegas et al.
INTRODUCTION
The successful application of heterogeneous catalysis in organic reactions has
been one of the most fruitful areas of green chemistry. Clay minerals are
silicate of aluminium with layered structures that present a wide use in
organic synthesis and exhibit specific features such as high versatility, gain
in yield and/or selectivity, low cost, and so forth.[1–3]
b-Iodoethers are useful intermediates in synthetic organic chemistry[4,5]
and are used in radiodiagnosis.[6] Several methodologies are known for their
preparation and, among them, the coiodination (iodination in the presence
of a nucleophilic solvent) of alkenes with alcohols mediated by metal salts
is well documented in the literature.[7]
Recently we published the hydroxyiodination (coiodination with water)
of several alkenes mediated by clay minerals as an efficient route for the prep-
aration of iodohydrins.[8] Continuing our interest in the cohalogenation of
alkenes,[9–12] we communicate here the results of the reaction of cyclohexene
with I2/alcohols in the presence of clays and compare the results with
traditional metal salt-mediated reactions.
RESULTS
The results of the reactions of cyclohexene with I2 and alcohols (ethanol, iso-
propanol, and t-butanol) in the presence of diverse catalysts at room tempera-
ture for 24 h are summarized in Table 1. The catalysts studied were clays
(a natural smectite Brazilian F-101 and the commercial montmorillonite
K-10) and metal salts (Cu2þ and Fe3þ). In all the reactions, the corresponding
trans-b-alkoxy-iodocyclohexane was formed as the unique organic product,
which was characterized by comparison of its spectral data with those
previously reported.[7,13,14] No diiodo compounds were detected in the
crude products by the analytical techniques employed (high-resolution gas
Table 1. Yields of trans-b-alkoxy-iodocyclohexanes
Catalyst
R
None
F-101
K-10
Cu(OAc)2
Fe2(SO4)3
Et
27%
23%
17%
90%
90%
72%
70%
71%
50%
92%
58%
50%
89%
63%
55%
i-Pr
t-Bu

Green Alkoxyiodination of Cyclohexane
1629
1
chromatography, H and 13C NMR) and although alcohols without further
purification were employed, no iodohydrin arising from small amounts of
water in the solvents was detected either.
All the catalysts used led to the same product and in the absence of any
catalyst the yield was very poor. The reactions mediated by Cu(OAc)2 and
Fe2(SO4)3 afforded the b-iodoethers in nearly the same yields. The best
results were obtained with the natural smectite Brazilian clay F-101. This
clay proved superior to commercial montmorillonite clay K-10 and this differ-
ence could be explained in terms of the higher Fe content of the former (10.11%
vs. 3.10%),[15] which is known to catalyze coiodination reactions.[9,16]
These results clearly show the great advantage of using a clay to perform
the reaction as the yields are higher, it is not toxic, the workup is easy (only a
filtration of the catalyst at the end of the reaction), and there is no metal iodide
residue as in the cases of metal salt–promoted reactions.
In summary, the preparation of trans-b-alkoxy-iodocyclohexanes from
the reaction of cyclohexene with I2 and alcohols is effective with promotion
by clays and metal salts. However, considering the environmental issues
that require the substitution of toxic catalysts by more friendly solid
catalysts and the advantages of heterogeneous catalysis in terms of ease of
workup, the utilization of clays is a better choice and consistent with green
chemistry philosophy.[17]
EXPERIMENTAL
General
All chemicals were used without further purification. K-10 was purchased
1
from Aldrich and F-101 was donated by Bentonit do Brasil (Brazil). H and
13C NMR were acquired on a Bruker AC-200 (200 and 50 MHz, respectively)
spectrometer in CDCl3 solutions with TMS as internal standard. Analyses by
HRGC were performed on a HP-5890-II gas chromatograph with flame ioniz-
ation detector (FID) by using a 28-m (length), 0.25-mm (ID), and 0.50-mm
(phase thickness) RTX-5 silica capillary column and He (flow rate
50 cm s21) as carrier gas (split 1 : 10). Mass spectra were obtained on a
Hewlett-Packard HP 5896-A HRGC-MS using electron impact (70 eV). IR
spectrum were recorded on a Perkin Elmer 1600 FT-IR or on a Nicolet 740
FT-IR spectrometers (NaCl film).
Typical Procedure for Coiodination of Cyclohexene with
Alcohols Mediated by Clays
To a stirred suspension of cyclohexene (5 mmol) and the clay (0.2 g) in the
appropriate alcohol (15 mL) was added iodine (10 mmol) in small portions

1630
R. A. S. Villegas et al.
at room temperature. After 24 h, the clay was filtered off, Et2O (10 mL) was
added, and the organic layer was washed with a saturated solution of
Na2S2O3 (3 ꢀ 5 mL). The organic extract was dried (anhydrous Na2SO4)
and filtered through a small column of SiO2. The solvent was evaporated on
a rotatory evaporator and then concentrated under reduced pressure (2 Torr)
and in a 508C bath to give the pure product as a colorless or light orange
oil. The purity of the trans-2-alkoxy-iodocyclohexenes (.99%) was
checked by comparison of the analytical data with that previously
reported[7,13,14] as well as by coinjection in HRGC in different conditions
that showed only one peak.
trans-1-Etoxy-2-iodocyclohexane. Bp 2358C (Lit.[13] 95–968C/8 Torr,
corrected[18] for 760 Torr: ca. 2398C). dH 1.24 (t, 3H, J 7.00 Hz), 1.30–1.61
(m, 4H), 1.7–2.2 (m, 3H), 2.37–2.48 (m, 1H), 3.32 (m, 1H), 3.60 (m, 2H),
4.04 (m, 1H, J 8.9 Hz) ppm. dC 15.8, 23.9, 27.4, 31.6, 36.2, 38.1, 65.0,
82.0 ppm. m/z 254, 127, 81 (100%), 57.
trans-1-Isopropoxy-2-iodocyclohexane. Bp 2548C (Lit.[13] 65–668C/1 Torr,
corrected[18] for 760 Torr: ca. 2508C). dH 1.16 (d, 3H, J 6.15 Hz), 1.23
(d, 3H, J 6.15 Hz), 1.28–1.57 (m, 4H), 1.79–2.14 (m, 4H), 3.38 (m, 1H),
3.78 (m, 1H), 4.02 (m, 1H, J 8.9 Hz) ppm. dC 22.8, 23.4, 24.0, 27.4, 33.2,
37.2, 38.4, 71.5, 80.7 ppm. nmax 2970, 2934, 2858, 1447, 1377, 1366, 1166,
1117, 1087, 661 cm21. m/z 268, 225, 141, 98, 81 (100%).
trans-1-t-Butoxy-2-iodocyclohexane. Bp not determined (decomposes
during determination of bp). dH 1.18 (s, 9H), 1.30–1.60 (m, 4H), 1.70–2.10
(m, 4H), 3.60 (m, 1H), 4.10 (m, 1H, J 8.0 Hz) ppm. dC 23.9, 27.4, 29.4,
31.2, 36.6, 38.7, 67.1, 82.7 ppm. m/z 282, 267 (100%), 209, 155, 81.
ACKNOWLEDGMENTS
We thank CNPq and FAPERJ for financial support and Bentonit do Brasil for
the kind donation of F-101. RASV and JLES thank CAPES and PIBIC/UERJ,
respectively, for fellowships.
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