Preparation of an aliphatic-substituted hypervalent iodine compound, tetracoordinate 1,2-iodoxetane 1-oxide, and its application to oxidation

Article abstract of DOI:10.1016/j.tetlet.2004.09.022

A tetracoordinate 1,2-iodoxetane oxide was prepared, and it oxidized alcohols to the corresponding aldehydes and ketones in good to moderate yields under mild conditions. A tetracoordinate 1,2-iodoxetane was prepared by the fluorination of a tricoordinate 1,2-iodoxetane with xenon difluoride followed by hydrolysis. The tetracoordinate 1,2-iodoxetane oxidized alcohols and a sulfide to the corresponding aldehydes and ketones, and a sulfoxide, respectively, in good to moderate yields under mild conditions.

Full text of DOI:10.1016/j.tetlet.2004.09.022

Tetrahedron
Letters
Tetrahedron Letters 45 (2004) 8173–8175
Preparation of an aliphatic-substituted hypervalent
iodine compound, tetracoordinate 1,2-iodoxetane 1-oxide,
and its application to oxidation
Naokazu Kano, Masaki Ohashi, Kazuhisa Hoshiba and Takayuki Kawashima*
Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
Received 18 August 2004; revised 3 September 2004; accepted 3 September 2004
Available online 21 September 2004
Dedicated to Professor Iwao Ojima, on the occasion of his 60th birthday
Abstract—A tetracoordinate 1,2-iodoxetane was prepared by the fluorination of a tricoordinate 1,2-iodoxetane with xenon difluo-
ride followed by hydrolysis. The tetracoordinate 1,2-iodoxetane oxidized alcohols and a sulfide to the corresponding aldehydes and
ketones, and a sulfoxide, respectively, in good to moderate yields under mild conditions.
Ó 2004 Elsevier Ltd. All rights reserved.
Hypervalent iodine compounds have found wide practi-
cal application as useful reagents for oxidation of a vari-
ety of primary and secondary alcohols to carbonyl
compounds.1–4 Both the Dess–Martin periodinane
(DMP) 1 and benziodoxole oxide (IBX) 2 have been
widely used as hypervalent iodine oxidants. These re-
agents have been applied to the organic synthesis of nat-
ural products despite their potentially explosive nature
1,2-Iodoxetane 3 (30mg, 0.062mmol) was heated with
and insolubility in certain common solvents. A majority
xenon difluoride (32mg, 0.19mmol) in CD3CN
(0.60mL) at 70°C for 14h and was monitored by 19F
of previous hypervalent iodine oxidants such as 1 and 2
are aryl-substituted iodine compounds. There are no
NMR spectroscopy (Scheme 1). A set of signals
examples of aliphatic-substituted iodinane oxides, to
our knowledge, because there are limited examples of
[dF À75.32 (t, 6F, JFF = 4.9Hz), À74.32 (t, 6F,
JFF = 8.5Hz), À25.45 to À25.75 (m, 2F)] increased with
alkyliodinanes that are expected to be precursors of
the alkyliodinane oxides.5–8 On the other hand, we pre-
a decrease of the signals of 3. The increased signals were
assigned to 1,2-iodoxetane 1,1-difluoride 4. Although an
viously reported the synthesis and thermolysis of 1,2-
iodinane difluoride was previously synthesized by treat-
iodoxetane 3 with a novel tridentate ligand.9 On one
ment of an iodinane with F2 gas,10 xenon difluoride is
hand oxidation of benzyl alcohol with 1,2-iodoxetane
much easier to handle than fluorine gas.11–14 The 1,2-
3 resulted in an unsatisfactory benzaldehyde yield;
iodoxetane 1,1-difluoride intermediate 4 was moisture
whereas on the other hand, an iodine compound with
sensitive and could not be isolated. The exposure of
an iodine atom in a higher oxidation state is expected
the reaction solution to aerial humidity resulted in the
to be a better oxidant. We report here the synthesis of
formation of the corresponding 1,2-iodoxetane 1-oxide
a tetracoordinate 1,2-iodoxetane 1-oxide and its applica-
tion as an oxidizing reagent. This is the first example of
an iodinane oxide with an aliphatic substituent.
Keywords: Iodine; Iodinane; 1,2-Iodoxetane; Oxidation.
*
Corresponding author. Tel./fax: +81 3 5800 6899; e-mail: takayuki@
chem.s.u-tokyo.ac.jp
Scheme 1. Preparation of 1,2-iodoxetane 1-oxide.
0040-4039/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2004.09.022

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N. Kano et al. / Tetrahedron Letters 45 (2004) 8173–8175
Table 1. Oxidation of primary and secondary alcohols with 1,2-iodoxetane oxide
Entry
R1R2CHOH
Equiv. of 5
Temp/°C
Time/h
Conv./%
Yield/%a
1
2
3
4
5
6
PhCH2OH
PhCH2OH
PhCH2OH
1.5
1.0
1.1
1.0
1.6
1.6
60
60
r.t.
75
70
70
2
7
100
96
79
73
66
23
81
77
36
15
6
87
93
Me3CCH2OH
PhCH(Me)OH
CH2@CHCH(Me)OH
100
100
6
a The yields were determined by 1H NMR spectroscopy using 1,3,5-tri-tert-butylbenzene as an internal standard.
contrast to the oxidation of 3-buten-2-ol with tricoordi-
nate iodoxetane 3 (1.5equiv) under more vigorous
conditions (90°C, 20h) resulting in the corresponding
ketone with a low yield (53%) and in low conversion
(20%).
Scheme 2. Thermolysis of 1,2-iodoxetane 1-oxide.
Although the selective formation of sulfides to sulfox-
ides by hypervalent reagents was previously reported
in oxidation reactions with several aryliodinanes17–22
or aryliodinane oxides,23 oxidation reactions with alkyl-
or alkenyl-iodinane have never been reported. When
diphenyl sulfide was subjected to oxidation with 5
(2.4equiv) at 70°C for 11h in CD3CN, diphenyl sulfox-
ide was formed with a 59% yield in 59% conversion
without the formation of diphenyl sulfone. Tricoordi-
nate 1,2-iodoxetane 3, which is formed in the reaction
mixture, oxidizes neither the substrates nor the products
under the reaction conditions.
5 (30% from 3) from 4.15 The recrystallization of the
crude mixture gave the pale brown waxy solid of 5,
which contained a small amount of impurities that could
not be removed.
The thermolysis of 5 at 120°C in CD3CN smoothly pro-
ceeded for 35h to produce alkynediol 6 (29%), alkene-
diol 7 (61%), and hexafluoroacetone (10%) (Scheme
2).16 The thermolysis of 5 proceeded under significantly
milder conditions than that of 3, which required a high
temperature for thermal decomposition.9 Compound 5
is not explosive under the thermal conditions in compari-
son with the potential explosiveness of 1 and 2. Com-
pound 5 is soluble in acetone, acetonitrile, DMF, and
DMSO, and slightly soluble in dichloromethane, though
it is almost insoluble in hexane, benzene, toluene, ether,
and chloroform. The solubility of 5 in the former sol-
vents and its tolerance to explosion encouraged us to ex-
plore its reactivity as an oxidant.
In summary, we have synthesized a new iodinane oxide
with an aliphatic substituent. We also demonstrate that
it can be used as an oxidizing reagent because it oxidizes
primary alcohols, secondary alcohols, and a sulfide
under mild conditions, with good to moderate yields.
Acknowledgements
The oxidation of benzyl alcohol with 5 (1.5equiv) at
60°C for 2h in CD3CN had a 79% yield of benzaldehyde
(Table 1, entry 1). The formation of iodoxetane was con-
firmed by the 19F NMR spectra. The usage of an equi-
molar amount of 5 in this reaction resulted in an
almost similar result except for the longer reaction time
and recovery of a trace amount of the starting alcohol
(entry 2). The reaction proceeded very slowly at room
temperature (entry 3). Another primary alcohol,
namely, neopentyl alcohol was similarly oxidized to pro-
duce pivalaldehyde in a low yield (23%) (entry 4). The
low yield of the aldehyde is explained by the steric con-
gestion of the neopentyl group.
This work was partially supported by Grants-in-Aid for
The 21st Century COE Program for Frontiers in Funda-
mental Chemistry (T.K.) and for Scientific Research
(T.K.) from the ministry of Education, Culture, Sports,
Science and Technology of Japan. We thank Central
Glass for the gift of organofluorine compounds.
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