Regioselective 1,2-alkoxy, hydroxy, and acetoxy iodination of alkenes with I2 catalyzed by Ce(SO3CF3)4

Article abstract of DOI:10.1016/S0040-4020(00)00358-6

The reaction of alkenes and iodine in water, alcohols and acetic acid is catalyzed with ceric triflate under mild conditions. The corresponding 1,2-alkoxy, acetoxy, and hydroxy iodides are obtained in good yields with easy procedure. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00358-6

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 5209±5211
Regioselective 1,2-Alkoxy, Hydroxy, and Acetoxy Iodination of
Alkenes with I2 Catalyzed by Ce(SO3CF3)4
*
Nasser Iranpoor and Marzieh Shekarriz
Chemistry Department, College of Sciences, Shiraz University, Shiraz 71454, Iran
Received 5 October 1999; revised 3 April 2000; accepted 20 April 2000
AbstractÐThe reaction of alkenes and iodine in water, alcohols and acetic acid is catalyzed with ceric tri¯ate under mild conditions. The
corresponding 1,2-alkoxy, acetoxy, and hydroxy iodides are obtained in good yields with easy procedure. q 2000 Elsevier Science Ltd. All
rights reserved.
The functionalization of alkenes is an important process in
organic synthesis.1 Recently, 1,2-chloro- and 1,2-bromo-
acetoxylation of alkenes with HCl gas in N,N-dimethyl-
acetamide/m-chloroperbenzoic acid or oxone1c and
PhI(OAc)2/Et4NBr1d, respectively were reported. The
reaction of halogen with alkenes in aqueous media is
considered a general method for synthesis of halohydrins.2,3
The reaction of alkenes with I2±H2O is carried out effec-
tively in the presence of AgNO3,4 HgO,5 CuO.HBF4,6
Cu(OAc)2,3 and oxidizing agents.7 Other routes for iodo-
functionalization of alkenes is the use of alkyl hypoiodites8
or iodine and a silver salt as reaction promoter followed by
addition of a nucleophile.9 However this latter method is
limited only to strong nucleophiles which can make stable
I±Nu compounds. This drawback was overcome by using
I(Py)2BF4 in MeOH, AcOH and water together with HBF4
or BF3, but still the method suffers from complexity of the
reagent and the acidic reaction conditions.9 In the course of
transformation, the reaction was performed in the presence
of 0.25 molar equivalents of various metal salts. The results
are summarized in Table 1.
The results in Table 1 show the ef®ciency of Ce(OTf)4
among the studied Lewis acids for this transformation.
This reaction was then studied for iodoalcoholysis of
some other alkenes.
The results obtained for alkoxy iodination of some other
alkenes are summarized in Table 2.
our studies10 on the applicability of Ce(SO3CF3)4 in
11
Scheme 1. Alkenes: RˆPh±, n-C6H11±, n-C16H33±, cyclohexene,
1-methylcyclohexene, indene R0ˆMe, Et, i-Pr, Ac, H.
synthesis, we observed its ability to act as catalyst for the
reaction of ole®ns with iodine in nucleophilic solvents. In
this work we report a very simple and ef®cient method for
alkoxy, acetoxy and hydroxy iodination of alkenes.
Table 1. Reactions of indene (1 mmol) with I2 (0.75 mmol) in MeOH/
dioxane (1:1) in the presence of various Lewis acids (0.25 mmol) at
room temperature
We studied the reaction of indene (1 mmol) and iodine
(0.75 mmol) in methanol/dioxane (1:1) in the presence of
0.25 molar equivalents of Ce(OTf)4 at room temperature
(Scheme 1). The reaction was found to be highly regio-
selective and only trans-1-methoxy-2 iodoindane was
obtained in 80% yield after 1 h together with 10±15%
unreacted indene. The same reaction in the absence of
Ce(OTf)4 produces only 10% of the product after 5 days.
In order to study the effect of Lewis acids on this
Lewis acid
Time (h)
trans-1-Methoxy-2-iodoindane (%)
NiCl2´6H2Oa
CuSO4
3
4
2
3
4
3
2
1
35
50
50
55
50
35
60
80
10
CeCl3´7H2Oa
Ce(NO3)6(NH4)2
b
Zn(NO3)2´6H2Ob
MgCl2´6H2Oa
Co(OAc)2´4H2O
Ce(OTf)4
Without catalyst
5 days
a Unreacted starting material (25±30%) together with 20±25% of 1-
chloro-2-iodoindane were obtained.
Keywords: alkoxy iodination; hydroxy iodination; acetoxy iodination;
alkene; ceric tri¯ate.
* Corresponding author. Fax: 198-71-20027;
e-mail: iranpoor@chem.susc.ac.ir
b In addition to the starting material (25±30%), a side product (10±15%)
was also obtained.
0040±4020/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00358-6

5210
N. Iranpoor, M. Shekarriz / Tetrahedron 56 (2000) 5209±5211
Table 2. 1,2-Iodofunctionalization of ole®ns (1 mmol) in the presence of I2 (0.75 mmol) and Ce(OTf)4 (0.25 mmol) at room temperature
Substrate
Solvent
Time (h)
1
Yield (%)
80
Producta
Reference to the product
8,9b
Cyclohexene
MeOH/dioxane (3:1)
Cyclohexene
EtOH/dioxane (3:1)
1.5
73
9b
Styrene
Styrene
MeOH/dioxane (2:1)
EtOH/dioxane (2:1)
1.5
2
80
82
PhCH(OMe)CH2I
PhCH(OEt)CH2I
8, 9a
8, 9a
Indene
Indene
Indene
MeOH/dioxane (1:1)
EtOH/dioxane (1:1)
i-PrOH/dioxane (1:1)
1
1.5
2
80
70
73
8
b
±
b
±
1-Octadecene
1-Octene
MeOH/dioxane (1:1)
MeOH/dioxane (1:1)
4
4
78
70
C16H31CH(OMe)CH2I1C16H31CHICH2OMe (76:24)c
C6H11CH(Ome)CH2I1C6H11CHICH2Ome (70:20)d
8
8
a Product was isolated and identi®ed by spectroscopic techniques.
b The product was compared with a known sample prepared according to the Ref. 8; 2-Iodo-1-ethoxyindane (Found: C, 45.6; H, 4.4; I, 44, C11H13IO requires
C, 45.8, H, 4.5, I, 44.1; 1H NMR d (ppm) 7.35 (2H, m), 7.15 (2H, m), 5.1 (1H, d), 4.4 (1H, m), 3.7 (3H, m), 3.25 (1H, m), 1.2 (3H, t); 13C NMR d (ppm)
141.0, 139.9, 133.0, 132.1, 128.4, 124.8, 66.2, 43.9, 42.7, 27.0, 16.2.; 2-Iodo-1-isopropoxyindane C, 47.6; H, 4.8; I, 42.1, C12H15IO requires C, 47.7, H,
4.96, I, 42.0; 1H NMR d (ppm) 7.35 (2H, m), 7.15 (2H, m), 5.1 (1H, d), 4.4 (1H, m), 4.0 (1H, m), 3.6 (1H, m), 3.2(1H, m), 1.1 (6H, d); 13C NMR d (ppm)
142.0, 141.5, 132.4, 129.1, 125.0, 124.8, 90.0, 72.6, 43.5, 28.2, 23.8, 23.0.
c Gc yield for distribution of the isomers, Rˆn-C16H31±.
d Gc yield for distribution of the isomers, Rˆn-C6H11±.
Table 3. 1,2- Iodofunctionalization of ole®ns (1 mmol) in the presence of I2 (0.75 mmol) and Ce(OTf)4 (0.25 mmol) at room temperature
Substrate
Solvent
Time (h)
Yield (%)
Producta
Reference to the product
Cyclohexene
H2O/dioxane (2:1)
3
75
3, 9b, 12
b
Cyclohexene
HOAc/dioxane (2:1)
HOAc/dioxane (2:1)
4
4
75
78
±
1-Methylcyclohexene
3, 9b
Styrene
Styrene
H2O/dioxane (2:1)
HOAc/dioxane (2:1)
3
3
88
83
PhCH(OH)CH2I
PhCH(OAc)CH2I
3, 9b
9b
Indene
Indene
H2O/dioxane (1:1)
2
1
75
60
12
c
HOAc/dioxane (1:1)
±
1-Octene
1-Octene
H2O/dioxane (1:1)
HOAc/dioxane (1:1)
5
5
72
70
RCH(OH)CH2I1RCHICH2OH (80:20)d
RCH(OAc)CH2I1RCHICH2OAc (70:30)d
13
±
a Product was isolated and identi®ed by spectroscopic techniques.
b trans-2- Iodo-1-acetoxycyclohexane (Found: C, 35.5; H, 4.6; I, 47.2, C8H13IO2 requires C, 35.8, H, 4.85, I, 47.4); 1H NMR d (ppm) 4.8 (1H, m), 4.0 (1H,
m), 2.3 (3H, s), 1.2±2.3 (8H, m); 13C NMR d (ppm) 170.3, 71.3, 67.4, 38.3, 32.0, 27.4, 23.9, 21.6.
c trans-2-Iodo-1-acetoxyindane (Found: C, 43.6; H, 3.5; I, 42.2, C11H11IO2 requires C, 43.7, H, 3.6, I, 42.0; 1H NMR d (ppm) 7.35 (1H, m), 7.15 (3H, m), 5.4
(1H, m), 4.2 (1H, m), 3.1 (2H, m), 2.2 (3H, s); 13C NMR d (ppm) 169.0, 133.9, 132.0, 127.3, 126.0, 123.5, 120.8, 62.0, 38.9, 21.1.
d Distribution of the isomers (Rˆn-C6H11±) was determined by gc and NMR analysis of the crude reaction mixture.

N. Iranpoor, M. Shekarriz / Tetrahedron 56 (2000) 5209±5211
5211
This reaction was also performed in water and acetic acid
and the corresponding 2-hydroxy- and 2-acetoxy iodides
were isolated in good yields. The results obtained are
shown in Table 3. The reaction of trans-stilbene in methanol
under similar reaction conditions was also studied, but no
reaction occurred under these conditions. This could be
due to steric effects for formation of the iodinium ion inter-
mediate. The high regioselectivity (except in the case of
1-octene and 1-octadecane) observed in these reactions is
controlled by electronic effects and attack of solvent
molecule occurs on that carbon atom which can effectively
stabilize the developing positive charge. In conclusion, 1,2-
alkoxy, hydroxy and acetoxy iodides can be easily prepared
from alkenes using ceric tri¯ate as catalyst. The availability
of the reagents and simplicity of the method, good yields
and high regioselectivity are considered as advantage of this
method.
added. The excess of iodine was removed by washing the
organic solution with 10% aqueous solution of Na2S2O3
(20 ml). The organic solution was further washed with
10% aqueous solution of NaHCO3 followed by water
(2£10 ml) and dried with anhydrous Na2SO4. The crude
product was puri®ed on a column of silica gel by using
petroleum ether: chloroform (5:1) as eluent. 2-Iodo-1-acet-
oxycyclohexane was obtained as colorless liquid in 75%
yield. Its elemental analysis and spectral data are given as
footnote in Table 2.
Acknowledgements
The authors are thankful to Shiraz University Research
Council for the partial support of this work.
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