Solvent-free conversion of alcohols into iodides with NaI supported on KSF clay

Article abstract of DOI:10.1080/00397910500297347

A variety of allylic, benzylic, primary, and secondary saturated alcohols have been converted into the corresponding iodides using NaI supported on KSF clay. Selective conversion of allylic and benzylic alcohols in the presence of primary and secondary saturated alcohols has also been demonstrated. Copyright Taylor & Francis, Inc.

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Solvent‐Free Conversion of
Alcohols into Iodides with NaI
Supported on KSF Clay
Mahmood Tajbakhsh a , Rahman Hosseinzadeh a ,
Zahra Lasemi a & Ali Rostami b
a Department of Chemistry, Mazandaran University,
Babolsar, Iran
b Department of Chemistry, University of Alberta,
Edmonton, Canada
Version of record first published: 22 Aug 2006.
To cite this article: Mahmood Tajbakhsh , Rahman Hosseinzadeh , Zahra Lasemi
& Ali Rostami (2005): Solvent‐Free Conversion of Alcohols into Iodides with NaI
Supported on KSF Clay, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 35:22, 2905-2911
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Synthetic Communicationsw, 35: 2905–2911, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910500297347
Solvent-Free Conversion of Alcohols into
Iodides with NaI Supported on KSF Clay
Mahmood Tajbakhsh, Rahman Hosseinzadeh, and
Zahra Lasemi
Department of Chemistry, Mazandaran University, Babolsar, Iran
Ali Rostami
Department of Chemistry, University of Alberta, Edmonton, Canada
Abstract: A variety of allylic, benzylic, primary, and secondary saturated alcohols
have been converted into the corresponding iodides using NaI supported on KSF
clay. Selective conversion of allylic and benzylic alcohols in the presence of
primary and secondary saturated alcohols has also been demonstrated.
Keywords: Iodination, KSF clay, solvent-free processes
INTRODUCTION
Halogen-containing compounds are very useful intermediates in organic
synthesis.[1] They react with nucleophiles such as amines or alkoxides to
give the corresponding substituted products and can be lithiated to
introduce electrophiles via a halogen–lithium exchange reaction.[2] The
prominent role of alkyl iodides in the formation of carbon–carbon bonds by
organometallic and free-radical reactions as well as by nucleophilic substi-
tutions has been well established.[3] The most common precursors to alkyl
halides are alcohols.[4] Therefore, the conversion of alcohols as readily
available starting materials into alkyl iodides is a frequently used functional
group-transformation.[5]
Received in the UK January 27, 2005
Address correspondence to Mahmood Tajbakhsh, Department of Chemistry,
Mazandaran University, Babolsar, Iran. Tel.: (þ98) 11252 34338; Fax: (þ98) 11252
42002; E-mail: tajbaksh@umz.ac.ir
2905

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M. Tajbakhsh et al.
Various methods have been devised in literature to achieve
this goal.[6] Some methods involve mild conditions and the use of
iodo,[7a] bromotrimethylsilanes,[7b] chlorotrimethylsilane-sodium iodide,[7c,d]
hexamethyldisilazane-iodine,[7e] P2I4 in CS2,[7f] chlorodiphenylphosphine,
iodine and imidazole,[7g] N,N-diethylaniline-borane-I2,[7h] CeCl3 7H2O/NaI
.
system,[7i] sodium iodide over KSF clay under microwave irradiation,[7j] KI/
H2SO4 supported on natural kaolinitic clay under microwave irradiation,[7k]
and NaI/Amberlyst 15[7l] as reagents. However, some of these methods
require toxic or hazardous materials, expensive reagents, long reaction time,
low yields, and tedious workup procedures. As such, mild and efficient
methods that can be used to promote the transformation of hydroxyl groups
into iodides are of increasing importance.
Solvent-free chemical synthesis has received much attention recently.[8]
Solvent-free processes are not only environmentally benign but are also econo-
mical.[9] Because a solvent is not required, toxic wastes can be minimized or
eliminated, and so the cost of solvent and waste treatment is reduced. Further-
more, operational simplicity is an attractive feature. Recent advances in this
area include, for example, aldol[10a,b] and related reactions,[10c] asymmetric-
catalyzed addition,[10d] and catalyzed cross-coupling reactions.[10e–j]
We now report a simple and efficient method for the conversion of
alcohols into iodides under mild conditions via treatment of the alcohols
with NaI supported on KSF clay at 608C (Scheme 1). In this method, a
substrate was added to sodium iodide and KSF clay, and the mixture was
ground in a mortar. The residue was then washed with a minimum amount
of diethyl ether. Evaporation of the solvent gave a product that is of acceptable
purity for most purposes.
RESULTS AND DISCUSSION
Several examples illustrating this procedure for the conversion of alcohols
into alkyl iodides are presented in Table 1. Evidently, a variety of allylic or
benzylic and saturated primary or secondary alcohols have been successfully
transformed into the corresponding iodides using NaI supported on KSF clay
at 608C in good yields. The iodination of benzyl alcohol was selected for
optimization of the reaction conditions. No transformation took place when
NaI without KSF clay were heated in water bath at 608C. This result
implies that KSF clay plays an important role in this reaction. This was
further confirmed when other solid supports such as SiO2, Al2O3, zeolite
HY, and montmorillonite K10 were employed. Treatment of benzyl alcohol
Scheme 1.

Alcohols into Iodides with NaI
2907
Table 1. Conversion of alcohols into alkyl iodides using NaI supported on KSF claya
Time Yield
(%)c
Entry
1
Substrate
Reagent
Productb
(h)
NaI, supported
on KSF clay
2
93
2
3
4
5
6
7
8
9
NaI, supported
on SiO2
5
4
20
10
10
60
95
85
90
84
NaI, supported
on Al2O3 (acidic)
NaI, supported on
montmorillonite
K10
4
NaI, supported
on zeolite HY
5
NaI, supported
on KSF clay
2
NaI, supported
on KSF clay
2.5
2.25
2
NaI, supported
on KSF clay
NaI, supported
on KSF clay
(continued)

2908
M. Tajbakhsh et al.
Table 1. Continued
Time Yield
(%)c
Entry
10
Substrate
Reagent
Productb
(h)
NaI, supported
on KSF clay
2
90
11
12
NaI, supported
on KSF clay
1.5
97
50
NaI, supported
on KSF clay
5
13
NaI, supported
on KSF clay
1
90
14
15
NaI, supported
on KSF clay
NaI, supported
on KSF clay
0.9
0.9
90
90
16
17
18
NaI, supported
on KSF clay
NaI, supported
on KSF clay
NaI, supported
on KSF clay
17
17
17
70
70
70
aAll reactions were carried out at 608C with an alcohol/NaI (1 : 1) molar ratio.
bAll products were characterized spectroscopically (IR, 1H NMR, GC) and showed
physical and spectral data in accordance with their expected structure by comparison
with authentic samples.[11,12]
cYields refer to pure isolated products.

Alcohols into Iodides with NaI
2909
with NaI/SiO2, NaI/Al2O3, and NaI/montmorillonite K10 gave the corre-
sponding iodide in low yield (Table 1, entries 2–4). Under the same con-
ditions, NaI/zeolite HY gave benzyl iodide in 60% yield (Table 1, entry 5).
Benzyl alcohol with NaI supported on KSF clay provided benzyl iodide in
excellent yield (Table 1, entry 1). We have tested various benzylic alcohols
with both electron-donating and electron-withdrawing groups on the aryl
ring (Table 1, entries 6–12). In the case of primary and secondary aliphatic
alcohols, the conversion into the corresponding iodides needs longer
reaction times (Table 1, entries 16–18). Furthermore, under the same
reaction conditions, allylic alcohols formed allylic iodides. It has been
observed that the attack of the iodide ion does not involve allylic rearrange-
ment (Table 1, entries 13 and 14). Displacement of allylic alcohols containing
a terminal double bond gave iodides accompanied by allylic rearrangement
(Table 1, entry 15) as observed by E. Marcantoni.[7i]
As mentioned, NaI supported on KSF clay under microwave irradiation
has been used for iodination only of benzylic alcohols to the corresponding
iodides.[7j] In their procedure, KSF clay was activated in vacuo to 2808C for
4 h. In our method, KSF clay was used without activating and significantly
extending the types of substrates.
Chemoselective iodination of allylic and benzylic alcohols was carried
out in the presence of saturated alcohols as well as a phenolic group. When
a mixture of equimolar amounts of benzyl alcohol and 1-heptanol were
treated with 1 equimolar NaI supported on KSF clay, only benzyl alcohol
was selectively converted to benzyl iodide, and 1-heptanol remained
unchanged. The results are shown in Scheme 2.
In conclusion, the present study provides a facile, convenient, and
efficient method for the conversion of alcohols into iodides under mild and
solvent-free conditions. The superiority of this method over the existing
Scheme 2.

2910
M. Tajbakhsh et al.
methods coupled with the ease of operation, the simplicity of workup, and the
environmental advantage makes the process very useful.
EXPERIMENTAL
General Procedure for Solvent-Free Conversion of Alcohols to
Iodides
Sodium iodide (0.150 g, 1 mmol), KSF clay (1 g), and alcohol (1 mmol) were
thoroughly mixed in a mortar and the resulting mixture was stirred in a flask at
608C. After completion of the reaction (TLC or GC), diethyl ether (10 ml) was
added and washed with aqueous saturated sodium hydrogen carbonate
solution, followed by deiodinization with sodium hydrogen sulfite. The
resultant organic layer was extracted with diethyl ether (3 ꢀ 10 ml), and
the combined extract was dried over anhydrous sodium sulfate. The solvent
was evaporated to afford the corresponding iodide in almost pure form. If
necessary, products were purified by column chromatography (eluent:
1
hexane–ethyl acetate). The products were identified by IR, H NMR, and
GC and by comparison with authentic samples.
ACKNOWLEDGMENTS
Financial support of this work from the Research Council of Mazandaran Uni-
versity is gratefully acknowledged.
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