Iodobenzene dichloride as a stoichiometric oxidant for the conversion of alcohols into carbonyl compounds; two facile methods for its preparation

Article abstract of DOI:10.1055/s-2007-965889

A highly efficient and mild procedure is described for the oxidation of different types of alcohols using 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO) as the catalyst, iodobenzene dichloride (PhICl₂) as a stoichiometric oxidant, and pyridine as the base. This procedure also smoothly oxidizes 1,2-diols to α-hydroxy ketones or α-diketones depending upon the amount of iodobenzene dichloride used. A competitive study shows that using the 2,2,6,6-tetramethylpiperidin-1-yloxy/iodobenzene dichloride/pyridine system aliphatic secondary alcohols are preferentially oxidized over aliphatic primary alcohols. In addition, two very convenient and high yielding procedures for the preparation of iodoarene dichlorides from iodoarenes have been developed. One employs solid sodium chlorite as a chlorinating agent in dilute hydrochloric acid solution; the other uses sodium hypochlorite as a chlorinating agent still in hydrochloric acid solution, which is more robust than the sodium chlorite system. Typically, the preparation of iodobenzene dichloride from iodobenzene was performed in five minutes using the sodium hypochlorite/hydrochloric acid system. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2007-965889

PAPER
551
Iodobenzene Dichloride as a Stoichiometric Oxidant for the Conversion of
Alcohols into Carbonyl Compounds; Two Facile Methods for Its Preparation
S
ynthesis andUse
u
of Iodobenzene Dichlor
-
ide Fei Zhao, Chi Zhang*
The State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, P. R. of China
Fax +86(22)23499247; E-mail: zhangchi@nankai.edu.cn
Received 15 September 2006; revised 8 November 2006
ported that iodobenzene dichloride oxidized secondary al-
Abstract: A highly efficient and mild procedure is described for the
oxidation of different types of alcohols using 2,2,6,6-tetramethylpi-
peridin-1-yloxy (TEMPO) as the catalyst, iodobenzene dichloride
(PhICl2) as a stoichiometric oxidant, and pyridine as the base. This
cohols to the corresponding ketones in moderate yields in
the presence of pyridine.11 The main drawback to this sim-
ple system was its inability to oxidize primary alcohols to
procedure also smoothly oxidizes 1,2-diols to a-hydroxy ketones or the corresponding aldehydes. Herein, we report the use of
a-diketones depending upon the amount of iodobenzene dichloride
used. A competitive study shows that using the 2,2,6,6-tetrameth-
ylpiperidin-1-yloxy/iodobenzene dichloride/pyridine system ali-
phatic secondary alcohols are preferentially oxidized over aliphatic
primary alcohols. In addition, two very convenient and high yield-
ing procedures for the preparation of iodoarene dichlorides from io-
doarenes have been developed. One employs solid sodium chlorite
as a chlorinating agent in dilute hydrochloric acid solution; the other
uses sodium hypochlorite as a chlorinating agent still in hydrochlo-
ric acid solution, which is more robust than the sodium chlorite sys-
tem. Typically, the preparation of iodobenzene dichloride from
iodobenzene was performed in five minutes using the sodium hy-
pochlorite/hydrochloric acid system.
a 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO) cata-
lyzed oxidation system with iodobenzene dichloride as
the stoichiometric oxidant and pyridine as the base for the
oxidization of primary and secondary alcohols to the cor-
responding aldehydes and ketones in excellent yields. We
also report two efficient, easily handled, and environmen-
tally benign procedures for the preparation of iodoarene
dichlorides from iodoarenes.
In the course of investigating the oxidative properties of
iodobenzene dichloride, we found that decan-1-ol was ox-
idized to decanal in quantitative yield with TEMPO (8
mol%), iodobenzene dichloride (1.5 equiv), and pyridine
(3 equiv) in chloroform (10 mL) at 50 °C (oil bath) for six
hours. Reducing the loading of catalyst TEMPO from 8
mol% to 5 mol% resulted in a decreased yield of decanal
(82%). When the reaction was carried out at room temper-
ature, the yield of decanal was 80% even after 18 hours.
The concentration effect was apparent in this reaction
since the reaction time was shortened from six to three
hours when the volume of chloroform was reduced from
10 mL to 5 mL. In addition, in the absence of pyridine, the
conversion of decan-1-ol was only 54% and decanal was
obtained in 48% yield after 18 hours. The solvent effect
on the oxidation of decan-1-ol was also examined, the re-
sults are summarized in Table 1.
Key words: iodobenzene dichloride, alcohols, catalysis, TEMPO,
oxidation
Iodobenzene dichloride, the first reported hypervalent io-
dine reagent, was synthesized by C. Willgerodt in 1886.1
Historically, it has been principally used as a chlorinating
reagent in organic synthesis replacing gaseous chlorine.2
Typically, Garvey, Halley, and Allen first observed that
the reaction of iodobenzene dichloride with unsaturated
hydrocarbons in refluxing 1,2-dichloroethane gave the
same products as when chlorine gas was used.3 Breslow et
al. have shown a number of beautiful examples of tem-
plate-directed chlorination of the C–H bond in steroids us-
ing iodobenzene dichloride as the chlorinating agent.4
Moreover, numerous applications of iodobenzene dichlo-
ride for the introduction of element chlorine into various
As shown in Table 1, chloroform appears to be the best
solvent among those tested, affording decanal in 94%
metal complexes have also been described.5 Another im- Table 1 Screened Solvents for the Oxidation of Decan-1-ola
pressive use of iodobenzene dichloride is its combination
Entry
Solvent
CHCl3
CH2Cl2
THF
Time (h)
Yield (%)
with lead(II) thiocyanate to effect the thiocyanation of
various organic substrates including silyl enol ethers,6 b-
dicarbonyl compounds,6 alkynes,7 phenols and naph-
thols.8 However, it appeared that the synthetic utility of
iodobenzene dichloride as an oxidizing agent was fairly
limited; the oxidation of aldoximes to nitrile oxides9 and
oxidative deoximation of ketoximes to the corresponding
ketones10 are two examples. In addition, Wicha et al. re-
1
2
3
4
5
6
3
3
3
3
3
3
94
50
69
62
56
57
PhMe
EtOAc
MeCN
SYNTHESIS 2007, No. 4, pp 0551–0557
Advanced online publication: 12.01.2007
DOI: 10.1055/s-2007-965889; Art ID: F15306SS
x
x
.
x
x
.2
0
0
7
a Reactions were performed with decan-1-ol (1 mmol), TEMPO (8
mol%), PhICl2 (1.5 equiv), pyridine (3 equiv), solvent (5 mL), 50 °C.
© Georg Thieme Verlag Stuttgart · New York

552
X.-F. Zhao, C. Zhang
PAPER
TEMPO (8 mol%)
CH3-(CH2)8-CH2OH
+
PhICl2 (1.5 equiv)
CH3-(CH2)8-CHO
94%
pyridine (3 equiv)
CHCl3 (5 mL), 50 °C, 3 h
Scheme 1 Optimal reaction conditions for the oxidation of decan-1-ol
yield (Table 1, entry 1). The yield of decanal was only It was observed that longer reaction times were required
50% when reaction was performed in dichloromethane; a for the oxidation of primary aliphatic alcohols compared
major factor in this case was the poor solubility of iodo- with that for a secondary alcohol (Table 2, entries 1, 2,
benzene dichloride in dichloromethane (Table 1, entry 2). and 3 vs entry 4). A competitive study was conducted in
Consequently, the optimal reaction parameters were fixed which a mixture of decan-1-ol (1 mmol) and octan-2-ol (1
and are given in Scheme 1.
mmol) was oxidized using 1.05 mmol of iodobenzene
dichloride and decanal and octan-2-one were obtained in
a 1:4.4 ratio. This finding confirmed that the TEMPO/
iodobenzene dichloride/pyridine oxidation system prefer-
entially oxidizes secondary alcohols over primary alco-
hols (Scheme 2). It should be noted that iodobenzene
diacetate/TEMPO preferentially oxidizes primary alco-
hols over secondary alcohols.12
A variety of alcohols, such as aliphatic primary and sec-
ondary alcohols, benzylic and allylic alcohols, were oxi-
dized to the corresponding carbonyl compounds in good
to excellent yields. Like decan-1-ol, two other aliphatic
primary alcohols with shorter or longer carbon chains, oc-
tan-1-ol and hexadecan-1-ol were smoothly oxidized to
their corresponding aldehydes in excellent yields
(Table 2, entries 2 and 3). As for secondary alcohols, oc- The mechanism of this alcohol oxidation reaction is worth
tan-2-ol and menthol were oxidized to the corresponding discussing. Firstly, the fact that the efficiency of this reac-
ketones in 98% and 93% yields, respectively (Table 2, en- tion decreased dramatically in the absence of pyridine
tries 4 and 5). 1-Phenylethanol and benzyl alcohol were suggested that this reaction is not an acid-catalyzed
excellent substrates under the standard oxidation condi- TEMPO dismutation process to give an oxoammonium
tions since their corresponding products were obtained in salt, which operated in a fairly similar oxidation system,
94% and quantitative yield, respectively (Table 2, entries iodobenzene diacetate/TEMPO.12 Accordingly, it is pro-
6 and 7). Notably, (2Z)-4-(tetrahydropyran-2-yloxy)but- posed that TEMPO is oxidized to its oxoammonium salt,
2-en-1-ol was oxidized to the corresponding aldehyde in which, as previously reported, is capable of oxidizing al-
77% yield without isomerization of the double bond
(Table 2, entry 8).
Table 2 Oxidation of Various Alcohols with Iodobenzene Dichlo-
ridea
The iodobenzene diacetate/TEMPO system developed by
Piancatelli et al. performs very well for the oxidization of
various primary and secondary alcohols and 1,3-diols to
their corresponding carbonyl compounds; 1,2-diols are,
however, cleaved to give the corresponding aldehydes.12
In our system, 1,2-diols could be successfully oxidized to
their corresponding a-hydroxy ketones or a-diketones de-
pending upon the number of equivalents of iodobenzene
dichloride used. For example, cyclooctane-1,2-diol was
oxidized using 1.1 equivalents of iodobenzene dichloride
to give 2-hydroxycyclooctan-1-one in 85% yield together
with cyclooctane-1,2-dione in 10% yield (Table 3, entry
1). Increasing the amount of iodobenzene dichloride to
three equivalents gave cyclooctane-1,2-dione in quantita-
tively yield as the sole product (Table 3, entry 2). In the
case of 1,2-diphenylethane-1,2-diol, as benzil is more sta-
ble than benzoin due to the conjugate effect, the ratio of a-
hydroxy ketone (benzoin) to a-diketone (benzil) is only
1.9:1 with 1.1 equivalents of iodobenzene dichloride,
which is much lower than in the case of cyclooctane-1,2-
diol (1.9:1 vs 8.5:1; Table 3, entry 3 vs entry 1).
Entry Alcohol
Time
Product
Yieldb
(%)
1
2
3
4
5
6
7
decan-1-ol
3 h
3 h
decanal
octanal
94
octan-1-ol
89
hexadecan-1-ol
octan-2-ol
4.5 h hexadecanal
1 h octan-2-one
92
98
menthol
45 min menthone
93
1-phenylethanol
benzyl alcohol
40 min acetophenone
40 min benzaldehyde
94
>99c
8
1.5 h
77
THPO
CH2OH
THPO
CHO
a Reaction conditions: alcohol (1 mmol), TEMPO (8 mol%), PhICl2
(1.5 equiv), pyridine (3 equiv), CHCl3 (5 mL), 50 °C
b Isolated yield.
c GC yield.
OH
O
TEMPO (8 mol%)
1 mmol
+
PhICl2 (1.05 mmol)
O
OH
pyridine (2.2 equiv)
CHCl3 (5 mL), 50 °C, 1 h
91%
GC ratio: 1:4.4
1 mmol
Scheme 2 Competitive reaction between decan-1-ol and octan-2-ol
Synthesis 2007, No. 4, 551–557 © Thieme Stuttgart · New York

PAPER
Synthesis and Use of Iodobenzene Dichloride
553
Table 3 Oxidation of 1,2-Diols
chlorine atom that is generated by the homolytic breaking
of the I–Cl bond in iodobenzene dichloride. Actually, the
fact that the oxoammonium salt is generated by the oxida-
tion of TEMPO by chlorine inspired us to propose that a
chlorine atom oxidizes TEMPO to its oxoammonium
salt.15 Then, the oxoammonium salt oxidizes the alcohol
to the corresponding carbonyl compound and is itself re-
duced to a hydroxylamine.13 The second chlorine atom is
thought to oxidize the hydroxylamine to TEMPO and the
catalytic cycle is complete (Scheme 3).
Using the iodobenzene diacetate/TEMPO system,12 1,2-
diols generate a five-membered ring intermediate after
ligand exchange twice between iodobenzene diacetate and
the 1,2-diol, which then collapses to give the cleavage
products, aldehydes.2a However, in our oxidation system,
the oxoammonium salt is thought to be the real oxidizing
agent and it can oxidize 1,2-diols to a-hydroxy ketones or
a-diketones smoothly without the formation of cleavage
products.16 This observation gives support to the proposed
mechanism.
Entry Diol
Time Product
Yielda
(%)
(h)
O
85
10
98
OH
OH
OH
O
1b
1
O
O
OH
OH
2c
5
3
O
O
O
52
28
99
OH
OH
3b
OH
We also investigated methods for the preparation of io-
doarene dichlorides. In 1886, Willgerodt developed the
most commonly used method for the preparation of iodo-
benzene dichloride by passing a stream of chlorine gas
into a solution of iodobenzene in chloroform at 0 °C.1 The
hazardous and inconvenient use of chlorine gas made the
development of an efficient, safe, and convenient protocol
for the preparation of iodobenzene dichloride from iodo-
benzene suitable for use in a synthetic laboratory desir-
able.
O
O
OH
O
4c
3
OH
a Isolated yield.
b PhICl2 (1.1 equiv), pyridine (2.2 equiv).
c PhICl2 (3 equiv), pyridine (6 equiv).
Mckillop et al. firstly described the preparation of iodo-
benzene dichloride by the oxidation of iodobenzene with
sodium perborate in either acetonitrile or carbon tetra-
chloride in the presence of hydrochloric acid, but it was
obtained in moderate yield only.17 Thereafter, Skulski et
cohols to the corresponding carbonyl compounds.13 Since
iodobenzene dichloride can decompose to release a chlo-
rine atom upon light irradiation or heating,14 we believed
that TEMPO is oxidized to the oxoammonium salt by a
.
I
.
I
Cl
Cl
Cl
Cl
I
I
.
Cl
.
Cl
+
+
hν or heat
hν or heat
.
Cl
+
Cl
N
N
O
O
.
R1
R2
CH OH
R1
HCl
C
O
+ HCl
.
R2
Cl
N
N
N
N
OH
⋅HCl
⋅HCl
N
Scheme 3 Proposed mechanism
Synthesis 2007, No. 4, 551–557 © Thieme Stuttgart · New York

554
X.-F. Zhao, C. Zhang
PAPER
Cl
Cl
al. reported a number of new procedures for the prepara-
tion of iodoarene dichlorides in which chlorine was gen-
erated in situ by the reaction of aqueous hydrochloric acid
with an appropriate oxidant such as potassium permanga-
nate, activated manganese dioxide, potassium chlorate,
sodium iodate trihydrate, concentrated nitric acid, sodium
carbonate–hydrogen peroxide, sodium persulfate, chro-
mium trioxide, and urea–hydrogen peroxide complex.18a–i
These procedures have different shortcomings, such as
complicated workup, use of toxic oxidants, high tempera-
tures, and low yields for some substrates. We have devel-
oped two complementary procedures for the preparation
of iodoarene dichlorides.
I
I
concd HCl (2 mL)
NaClO2 (5 equiv)
+
H2O (5 mL), r.t., 3 h
1 mmol
99%
Scheme 4 Optimal reaction conditions for the preparation of iodo-
benzene dichloride by sodium chlorite
ing group like 4-iodoanisole was oxidized to the
corresponding dichloride in 92% yield (Table 4, entry 3).
For 1-iodo-3-nitrobenzene and 1-iodo-4-nitrobenzene, the
reaction rates were slow because of their poor solubility in
water. This problem was overcome by the addition of
acetonitrile (2 mL) as a co-solvent (Table 4, entry 9 vs 10
and entry 11 vs 12).
Sodium chlorite (NaClO2) is a mild oxidant that has vari-
ous applications in industry and synthetic organic chemis-
try. Our laboratory has recently developed a convenient
method for the synthesis of epoxides from alkenes using
sodium chlorite as the terminal oxidant without the use of
a catalyst.19 Starting from this work, we were interesting
in exploring new reactivity of sodium chlorite. What we
found was an efficient method for the preparation of io-
doarene dichlorides from iodoarenes in dilute hydrochlo-
ric acid solution using sodium chlorite as an oxidant and
acetonitrile as a co-solvent if necessary. The optimal reac-
tion conditions are described in Scheme 4 with which io-
dobenzene could be oxidized to iodobenzene dichloride in
99% yield.
It has been reported that sodium chlorite reacts with hy-
drochloric acid to generate chlorine dioxide (ClO2).20 The
reaction shown in Scheme 4 was monitored by UV spec-
troscopy and the characteristic peak of chlorine dioxide
was observed. Moreover, chlorine dioxide was prepared
according to a reported method; i.e., mixing of oxalic acid
and potassium chlorate in water;21 then it was passed into
a suspension of iodobenzene in hydrochloric acid solu-
tion. After three hours, iodobenzene dichloride was ob-
tained in 44% yield. Therefore, chlorine dioxide is
believed to be the key agent in the chlorination of iodo-
benzene.
A wide range of iodoarenes were oxidized to their corre-
sponding dichlorides in excellent yields (Table 4, entries
1–8). Both electron-withdrawing and electron-donating
functional groups were tolerated under the reaction condi-
tions. Notably, an iodoarene with a strong electron-donat-
Sodium hypochlorite is a frequently used chlorine-based
oxidant and it can react rapidly with hydrochloric acid to
generate chlorine,22 which could be used to chlorinate io-
dobenzene to give iodobenzene dichloride. As expected,
Table 4 Preparation of Iodoarene Dichlorides with Sodium Chloritea
Entry
1
Substrate
Time (h)
Product
Yield (%)
99
Mp (°C)
111–113
97–98
72–74
75–77
98–99
94–96
121–123
113–114
87
Lit. mp (°C)
111–11218i
97–9818f
75–7618i
79–8018i
–
PhI
3
11
2
PhICl2
2
4-MeC6H4I
4-MeOC6H4I
2-FC6H4I
4-MeC6H4ICl2
4-MeOC6H4ICl2
2-FC6H4ICl2
2-BrC6H4ICl2
3-BrC6H4ICl2
4-BrC6H4ICl2
4-ClC6H4ICl2
3-O2NC6H4ICl2
3-O2NC6H4ICl2
4-O2NC6H4ICl2
4-O2NC6H4ICl2
99
3b
4
92
8.5
11.5
7
99
5
2-BrC6H4I
3-BrC6H4I
4-BrC6H4I
4-ClC6H4I
3-O2NC6H4I
3-O2NC6H4I
4-O2NC6H4I
4-O2NC6H4I
93
6
96
–
7
11.5
4
94
123–12418b
113–11518i
89–9018b
–
8
95
9
24
6
74
10b
11
12b
94
–
24
6
63
172–174
–
175–17618i
–
95
a Conditions: iodoarene (1 mmol), NaClO2 (5 equiv), concd HCl (2 mL), H2O (5 mL), r.t.
b MeCN (2 mL) was added as a co-solvent.
Synthesis 2007, No. 4, 551–557 © Thieme Stuttgart · New York

PAPER
Synthesis and Use of Iodobenzene Dichloride
555
this was the case and sodium hypochlorite/hydrochloric dichloride are also reported. It is 120 years since the dis-
acid brought about a drastic increase in the reaction rate covery of iodobenzene dichloride in the year of 1886, the
compared with sodium chlorite/hydrochloric acid system new reactivity of iodobenzene dichloride reported here
since the preparation of iodobenzene dichloride from io- expands its synthetic application. Further studies on the
dobenzene was complete in five minutes (Scheme 4 vs synthetic utility of iodobenzene dichloride as an oxidizing
Scheme 5). The optimal reaction conditions are described reagent are underway in our laboratory.
in Scheme 5.
NaClO2 (80% purity), TEMPO, NaOCl (5.84%) were purchased
I
Cl
Cl
from commercial suppliers and used without further purification.
CHCl3 and pyridine were distilled before use. The thermal stability
of PhICl2 is good; it could be stored at ca. 5 °C for >3 months with-
I
concd HCl (2 mL)
15 °C, 5 min
+
NaClO (5.84%, 6 mL)
1
out any change in its melting point and H NMR spectrum. The
known carbonyl products were identified by comparison of their 1H
and 13C NMR spectrums with those reported in literature. The io-
doarene dichlorides were identified by comparison to their literature
melting points. The 1H NMR spectra were recorded at 300 MHz or
400 MHz. and 13C NMR spectra were measured at 75 MHz or 100
MHz, using CDCl3 as the solvent.
1 mmol
99%
Scheme 5 Optimal reaction conditions for the preparation of iodo-
benzene dichloride by sodium hypochlorite
A number of iodoarenes were successfully chlorinated to
their corresponding dichlorides in excellent yields and
generally, these reactions proceeded at much faster reac-
tion rate than that of the sodium chlorite/hydrochloric acid
system (Table 5). It was worth indicating that 4-iodoani-
sole could not be oxidized to its dichloride using this pro-
tocol. Moreover, this method could be scaled up to 200
mmol of iodobenzene, producing 53 grams of iodoben-
zene dichloride after each run.
Decanal; Typical Procedure
PhICl2 (412.5 mg, 1.5 mmol) was added to a soln of decan-1-ol (158
mg, 1 mmol), TEMPO (12.5 mg, 0.08 mmol), and pyridine (0.26
mL, 3 mmol) in CHCl3 (5 mL) at r.t. The reaction flask was placed
in an oil bath at 50 °C and reaction was monitored by TLC. After 3
h, the mixture was cooled to r.t. and diluted with CH2Cl2 (50 mL).
The resulting mixture was washed sequentially with sat. aq Na2S2O3
(1 × 10 mL), 1 M HCl (1 × 10 mL), and brine (1 × 20 mL). The or-
ganic layer was dried (anhyd Na2SO4) and concentrated in vacuo to
afford the crude product, which was purified to remove PhI and
TEMPO by flash column chromatography (petroleum ether–
EtOAc, 49:1) to give decanal as colorless oil; yield: 147 mg (94%).
An efficient and mild alcohol oxidation method using io-
dobenzene dichloride as the stoichiometric oxidant cata-
lyzed by TEMPO has been developed. 1,2-Diols could be
oxidized to a-hydroxy ketones or a-diketones without the
formation of the product of oxidative cleavage. Compared
with other hypervalent iodine reagent based alcohol oxi-
dation systems,23 the oxidant, iodobenzene dichloride,
used in our protocol is efficient and readily available since
two convenient preparative procedures of iodobenzene
Iodobenzene Dichloride Using Sodium Chlorite; Typical Proce-
dure
NaClO2 (566 mg, 5 mmol) was added portionwise over 10 min to a
stirred soln of PhI (204 mg, 1 mmol) in dil HCl [made by mixing
concd HCl (2 mL) and H2O (5 mL)] at r.t. The mixture was stirred
for 3 h. The resulting yellow precipitate was collected by filtration,
washed with H2O and light petroleum ether, and dried at r.t. in the
dark overnight. The yellow solid was identified to be PhICl2 by
Table 5 Preparation of Iodoarene Dichlorides with Sodium Hypochloritea
Entry
1
Substrate
PhI
Time (min)
Product
Yield (%)
99
Mp (°C)
112–113
96–97
Lit. mp (°C)
111–11218i
97-9818f
79–8018i
–
5
60
45
40
40
60
45
40
40
80
PhICl2
2
4-MeC6H4I
2-FC6H4I
2-BrC6H4I
3-BrC6H4I
4-BrC6H4I
4-ClC6H4I
3-O2NC6H4I
4-O2NC6H4I
4-PhC6H4I
4-MeC6H4ICl2
2-FC6H4ICl2
2-BrC6H4ICl2
3-BrC6H4ICl2
4-BrC6H4ICl2
4-ClC6H4ICl2
3-O2NC6H4ICl2
4-O2NC6H4ICl2
4-PhC6H4ICl2
100
98
3
76–77
4
98
97–98
5
99
95–96
–
6b
7b
8b
9b
10b
96
121–122
112–113
90
123–12418b
113–11518i
89–9018b
172–17318i
85–8718j
98
98
99
172–173
85–87
94
a Conditions: iodoarene (1 mmol), 5.84% NaOCl (6 mL), concd HCl (2 mL), 15 °C.
b MeCN (2 mL) was used as a co-solvent.
Synthesis 2007, No. 4, 551–557 © Thieme Stuttgart · New York

556
X.-F. Zhao, C. Zhang
PAPER
comparison of its mp with that reported in the literature and its pu-
rity was 98.5% as determined by iodometric titration; yield: 272 mg
(99%).
(2Z)-4-(Tetrahydropyran-2-yloxy)but-2-enal (Table 2, Entry
8)29
1H NMR (400 MHz, CDCl3): d = 9.52 (d, J = 8 Hz, 1 H), 6.79–6.85
(m, 1 H), 6.30–6.36 (m, 1 H), 4.62 (t, 1 H), 4.43–4.49 (m, 1 H),
4.17–4.22 (m, 1 H), 3.76 (t, J = 7.2 Hz, 1 H), 3.45–3.48 (m, 1 H),
1.48–1.77 (m, 6 H).
Iodobenzene Dichloride Using Sodium Hypochlorite; Typical
Procedure
Concd HCl (2 mL) was added dropwise over 2 min to a stirring soln
of iodobenzene (204 mg, 1 mmol) in aq 5.84% NaOCl soln (6 mL)
at r.t. A yellow solid precipitated immediately and the reaction was
complete after 5 min (TLC analysis). The resulting yellow solid was
collected by filtration, washed with H2O and light petroleum ether,
and dried at r.t. in the dark overnight. The yellow solid was identi-
fied to be PhICl2 by comparison of its mp with that reported in the
literature. Its purity was 99% as determined by iodometric titration;
yield: 271 mg (99%).
13C NMR (100 MHz, CDCl3): d = 193.36, 153.39, 131.42, 98.25,
65.44, 62.04, 30.24, 25.22, 19.02.
2-Hydroxycyclooctan-1-one (Table 3, Entry 1)30
1H NMR (400 MHz, CDCl3): d = 4.18 (t, J = 7.2 Hz, 1 H), 3.73 (s,
1 H), 2.71–2.72 (m, 1 H), 2.34–2.35 (m, 2 H), 1.95–2.05 (m, 2 H),
1.59–1.81 (m, 4 H), 1.37–1.39 (m, 2 H), 0.88–0.92 (m, 1 H).
13C NMR (100 MHz, CDCl3): d = 217.38, 75.99, 37.07, 29.13,
28.38, 25.27, 24.25, 21.90.
Iodobenzene Dichloride; Typical Large-Scale Procedure with
Sodium Hypochlorite
Cyclooctane-1,2-dione (Table 3, Entry 2)31
1H NMR (400 MHz, CDCl3): 2.51–2.54 (t, J = 7.2 Hz, 4 H), 1.72–
1.73 (m, 4 H), 1.56–1.58 (m, 4 H).
13C NMR (100 MHz, CDCl3): d = 210.05, 29.93, 26.33, 21.11.
Aq 5.84% NaOCl soln (800 mL) was added dropwise over 1 h to a
vigorously stirred soln of iodobenzene (22.4 mL, 200 mmol) in con-
cd HCl (200 mL) at r.t. Stirring was continued for a further 0.5 h
when the addition of NaOCl was complete. The precipitated yellow
solid was collected by filtration, washed with H2O and light petro-
leum ether, and dried at r.t. in the dark overnight; yield: 52.9 g
(96%).
Benzoin (Table 3, Entry 3)32
1H NMR (400 MHz, CDCl3): d = 7.90–7.91 (d, J = 7.2 Hz, 2 H),
7.48–7.51 (m, 1 H), 7.24–7.39 (m, 7 H), 5.95 (d, J = 6 Hz, 1 H), 4.58
(d, J = 6 Hz, 1 H).
Decanal (Table 2, Entry 1)24
13C NMR (100 MHz, CDCl3): d = 198.85, 138.90, 133.85, 133.36,
129.07, 128.62, 128.50, 127.70, 76.14.
1H NMR (400 MHz, CDCl3): d = 9.69 (s, 1 H), 2.33–2.37 (m, 2 H),
1.52–1.57 (m, 2 H), 1.19–1.29 (m, 12 H), 0.81 (t, J = 7.2 Hz, 3 H).
13C NMR (100 MHz, CDCl3): d = 202.73, 43.83, 31.77, 29.29,
Benzil (Table 3, Entry 4)33
1H NMR (400 MHz, CDCl3): d = 7.98 (d, J = 8 Hz, 4 H), 7.66–7.68
(m, 2 H), 7.50–7.54 (m, 4 H).
29.17, 29.09, 22.57, 22.00, 13.99.
Octanal (Table 2, Entry 2)25
13C NMR (100 MHz, CDCl3): d = 194.51, 134.83, 132.82, 129.78,
128.93.
1H NMR (400 MHz, CDCl3): d = 9.69 (s, 1 H), 2.33–2.36 (m, 2 H),
1.54–1.57 (m, 2 H), 1.21–1.23 (m, 8 H), 0.80 (t, J = 7.2 Hz, 3 H).
13C NMR (100 MHz, CDCl3): d = 202.92, 43.89, 31.59, 29.09,
28.99, 22.56, 22.05, 14.02.
Acknowledgment
This work was financially supported by The National Natural
Science Foundation of China (No. 20572046 and No. 20421202),
the 111 Project (B06005), and the Ministry of Education of China.
Hexadecanal (Table 2, Entry 3)26
1H NMR (400 MHz, CDCl3): d = 9.69 (s, 1 H), 2.33–2.37 (m, 2 H),
1.53–1.57 (m, 2 H), 1.18–1.22 (m, 24 H), 0.81 (t, J = 7.2 Hz, 3 H).
13C NMR (100 MHz, CDCl3): d = 202.84, 43.88, 31.90, 29.64,
29.33, 29.14, 22.66, 22.05, 14.09.
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Synthesis 2007, No. 4, 551–557 © Thieme Stuttgart · New York