Chlorination of various substrates in subcritical carbon tetrachloride

Article abstract of DOI:10.1016/j.tet.2010.02.021

Various aliphatic hydrocarbons and the side chains of aromatic hydrocarbons were chlorinated in subcritical carbon tetrachloride. Chlorination of aromatic compounds including 1,4-disubstituted benzenes was investigated. Ketones and sulfones were stable under the employed conditions. Sulfoxides were converted into sulfides in a low to modest yields. The coupling adducts between olefins and carbon tetrachloride were obtained from the reactions of olefins.

Full text of DOI:10.1016/j.tet.2010.02.021

Tetrahedron 66 (2010) 2881–2888
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Chlorination of various substrates in subcritical carbon tetrachloride
,
a
a
b
Kiyoshi Tanemura a , Tsuneo Suzuki , Yoko Nishida , Takaaki Horaguchi
*
a School of Life Dentistry at Niigata, Nippon Dental University, Hamaura-cho, Niigata 951-8580, Japan
b Department of Chemistry, Faculty of Science, Niigata University, Ikarashi, Niigata 950-2181, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Various aliphatic hydrocarbons and the side chains of aromatic hydrocarbons were chlorinated in sub-
critical carbon tetrachloride. Chlorination of aromatic compounds including 1,4-disubstituted benzenes
was investigated. Ketones and sulfones were stable under the employed conditions. Sulfoxides were
converted into sulfides in a low to modest yields. The coupling adducts between olefins and carbon
tetrachloride were obtained from the reactions of olefins.
Received 17 December 2009
Received in revised form 2 February 2010
Accepted 2 February 2010
Available online 10 February 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Subcritical conditions
Carbon tetrachloride
Chlorination
Radical reactions
1. Introduction
2. Results and discussions
Much attention has been paid to supercritical and subcritical
water as a medium for chemical reactions, since it has quite unique
properties such as low polarity and the change of the pKw value
(pKw¼11.2 at 250 ꢀC).1 Supercritical alcohols are also attractive
solvents because of unique reactivities such as direct addition of
alcohols to alkenes.2
Direct introduction of halogen substituents into various classes
of organic molecules can be achieved by free-radical reactions.
Especially, halogenation of aliphatic hydrocarbons and side chains
of aromatic hydrocarbons has been reported by many re-
searchers.3–5
In our continuing studies concerning the halogenation of or-
ganic compounds,6 we were interested in the chlorination of or-
ganic compounds under high temperature conditions. We planned
to chlorinate organic substrates by the reactions of chloro radical
generated from the C–Cl bond cleavage of carbon tetrachloride
under high temperature conditions. We have reported the chlori-
nation of some typical compounds in high temperature carbon
tetrachloride as the preliminary communication.7 As an extension
of the work, this paper describes full details of the reactions of
a variety of compounds, including the reactions of 1,4-disubstituted
benzenes.
First, adamantane (1) was chosen as the model compound of al-
iphatic hydrocarbons. The critical temperature of carbon tetrachlo-
ride is 283 ꢀC.8 The reactionwas conducted at 250 ꢀC on 7 MPa for4 h
to give 1-chloroadamantane (2), 1,3-dichloroadamantane (3), and 2-
chloroadamantane (4) in 52, 9, and 3% yields, respectively (Caution!,
seeExperimental section)(Table 1, entry1). Prolongedheatingfor9 h
gave the dichloro compound 3 in 73% yield together with small
amounts of 2 (4%) and 4 (2%) (entry 2). When the reaction was
performed at 300 ꢀC, the Teflon crucible equipped in the stainless
autoclave melted in spite of the good yield (60%) of 2 (entry 3). We
carried out all the reactions at 250 ꢀC because of the above reason.
When chloroform and dichloromethane were employed as solvents,
monochloride 2 was obtained in low yields (31 and 6% yields,
respectively) (entries 4 and 5). Chlorocyclododecane (6) and
dichlorocyclododecane (7) were produced in 35 and 12% yields from
the reaction of 5 at 250 ꢀC for 7 h in subcritical carbon tetrachloride,
respectively (entry 6). Dichloride 7 was obtained as an inseparable
mixture. The positions of the second chlorine atom in 7 are not clear.
The reaction of 2,2,3,3-tetramethylbutane (8) gave 1-chloro-2,2,3,3-
tetramethylbutane (9) in a low yield (3%) (entry 7). The relative ease
of substitution of hydrogen was tertiary>secondary>primary. The
methyl group of tert-butylbenzene (10) is so unreactive toward or-
dinary photochemical methods.9 However, it can be chlorinated with
ease by the use of sulfuryl chloride-benzoyl peroxide (BPO) to give 1-
chloro-2-methyl-2-phenylpropane (11).9 In contrast, the rearranged
product, 2-chloro-2-methyl-1-phenylpropane was yielded by gas-
phase photochlorination.4 Compound 10 was almost unreactive in
* Corresponding author. Fax: þ81 25 267 1134.
E-mail address: tanemura@ngt.ndu.ac.jp (K. Tanemura).
0040-4020/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.02.021

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K. Tanemura et al. / Tetrahedron 66 (2010) 2881–2888
subcritical carbon tetrachloride (entry 8). Prolonged heating of 10 for
21 h gave chloride 11 in 19% yield accompanying large amounts of
polymeric materials (entry 9).
Table 1
The reactions of various hydrocarbons in high temperature solventsa
The reactions of the side chains of aromatic hydrocarbons were
examined. Toluene (12) was chlorinated at the benzylic position in
subcritical carbon tetrachloride (entry 10). Reactions of diphenyl-
methane (14) and triphenylmethane (16) gave chlorides 15 and 17
in 53 and 99% yields, respectively (entries 11 and 12). The yields of
the products were increased with the introduction of the phenyl
group, since the resulting radical became more stable. Chlorination
of 1-methylnaphthalene (18) led to the formation of chloride 19
and dichloride 20 in 36 and 37% yields, respectively (entry 13). We
conducted the chlorination of compound 21, which possesses both
of the methine group and the benzylic position. Indeed, chlorina-
tion of 21 occurred predominantly at the benzylic position under
subcritical conditions (entry 14).
Entry
Substrate
Time
(h)
Products
Recovery
(%)b
(Yield (%)b)
Cl
Cl
Cl
1
4
(15)
C
1
4 (3)
(52)
(9)
3
2
2
1
1
1
1
9
2
4
4
2 (4)
2 (60)
2 (31)
2 (6)
3 (73)
3 (21)
3 (0)
4 (2) (0)
4 (4) (0)
4 (0) (49)
4 (0) (76)
3c
4d
5e
3 (0)
Cl
Cl
Next, we attempted the reactions of a variety of aromatic com-
pounds at 250 ꢀC for 7 h. The results are summarized in Table 2.
Nitrobenzene (24) was easily converted into chlorobenzene (25)
(entry 1). Several reports including photo-initiated chlorination3
and gas-phase reactions10 for the transformation of 24 to 25 have
been reported. Halogen exchange reactions were investigated. Flu-
orobenzene (26) was recovered without any changes after 7 h (entry
2). Chlorobenzene (25) was stable under the employed conditions
and further nuclear substitution did not proceed (entry 3). Trans-
formation of bromobenzene (27) to chlorobenzene (25) proceeded
smoothly (entry 4). Many reports have been known for chlorode-
bromination of bromobenzene (27) by photo-induced chlorina-
tion,11–13 the use of sulfuryl chloride-BPO13 and gas-phase
6
7
7
7
(34)
Cl
5
8
7
6 (35)
(12)
CH Cl
2
(95)f
(3)f
9
CH2Cl
8
7
(96)f
(45)f
(74)f
11 (3)f
10
9
10
21
7
11 (19)f
Table 2
CH3
CH2Cl
a
The reactions of nitro and halogen derivatives ArX in high temperature CCl4
10
Entry
Substrate
Products (Yield (%)b)
Recovery (%)b
12
13 (24)f
NO2
Cl
1
(0)
Cl
CH2
CH
(90)
24
25
11
12
13
7
7
7
(42)
(0)
14
(53)
F
15
2
3
4
5
N.R.f
(97)
(99)
(0)
26
25
CH
C
Cl
Cl
Br
I
N.R.f
(99)
17
16
CH3
CH2Cl
CHCl2
Cl
Cl
(5)
(36)
(37)
20
19
18
27
28
25 (94)
CH3
CH3
CH2Cl
(0)
14
4
(32)
25 (50)g
Cl
6c
7d
8e
28
28
28
25 (90)
25 (31)
25 (13)
(0)
(65)
(84)
23 (4)
21
22 (47)
a
Reagents and conditions: Substrates 4.0 mmol, solvent 15 mL, temp 250 ꢀC, N2.
a
Reagents and conditions: Substrates 4.0 mmol, CCl4 15 mL, temp 250 ꢀC, time
b
c
d
e
f
Isolated yields.
Temp 300 ꢀC.
Solvent CHCl3.
Solvent CH2C12.
7 h, N2.
b
The yields were calculated on the basis of the peak of 1,4-dioxane using 1H NMR
spectroscopy.
c
Temp 240 ꢀC.
The yields were calculated on the basis of the peak of 1,4-dioxane using 1H NMR
d
e
f
Temp 220 ꢀC.
spectroscopy.
Temp 200 ꢀC.
No reaction.
Complex mixture was obtained.
g

K. Tanemura et al. / Tetrahedron 66 (2010) 2881–2888
2883
chlorination.10 Although the yield of chlorobenzene (25) was low
Table 4
a
Chlorination of 35 in high temperature CCl4
(50%) at 250 ꢀC because of the production of large amounts of
decomposed materials, chlorobenzene (25) was obtained at 240 ꢀC
in the quantitative yield (90%) from the reaction of iodobenzene (28)
(entries 5 and 6). It was reported that chlorodeiodination occurred
by use of sulfuryl chloride-BPO, while iodobenzene dichloride was
produced by photo-induced chlorination of iodobenzene.11,14,15
Iodobenzene dichloride is the somewhat unstable compound,
which decomposes on heating above the melting point (ca. 101–
103 ꢀC), affording chiefly p-chloroiodobenzene.14b These materials
were not detected by 1H NMR spectroscopy and T.L.C. in our ex-
periments achieved at 200–250 ꢀC, indicating that iodobenzene (28)
was transformed to chlorobenzene (25), exclusively (entries 5–8).
Chlorionation of 1,4-disubstituted benzenes was examined. The
results were summarized inTable 3. p-Chloronitrobenzene (29) and p-
bromochlorobenzene (31) were transformed to p-dichlorobenzene
(30) in 90 and 13% yields, respectively (entries 1 and 2). The nitro and
Entry
Time (h)
Recovery (%)b
35
Products (Yield (%)b)
29
31
30
1
2
3
4
5
6
7
1.0
2.0
2.5
3.0
4.0
5.0
7.0
98
74
49
0
0
0
0
5
6
8
0
0
0
0
0
0
0
0
0
0
0
14
36
83
92
92
93
0
a
Reagents and conditions: 35 4.0 mmol, CCl4 15 mL, temp 250 ꢀC, N2.
b
The yields were calculated on the basis of the peak of 1,4-dioxane using 1H NMR
spectroscopy.
Table 3
a
The reactions of p-substituted benzenes in high temperature CCl4
Entry Substrate
Products (Yield (%)b)
Recovery (%)b
NO2
Cl
1
(0)
Cl
Cl
29
30 (90)
Br
Cl
2c
(75)
(0)
Cl
Figure 1. The time course of the reaction of p-bromonitrobenzene (35).
Cl
F
30 (13)
33 (94)
33 (91)
31
32
34
bromo groups were converted into the chloro group without the
changesofthefluorogroup,indicatingthatthefluorogroupwasstable
under the employed conditions (entries 3 and 4).
F
3
p-Bromonitrobenzene (35) was transformed to 30 in 93% yield
after 7 h (entry 5). Detailed studies were conducted for the chlori-
nation of compound 35. The product distributions through the
progress of the reaction are summarized in Table 4 and Figure 1. The
reaction pathway for the reaction of 35 is shown in Scheme 1. As
shown in Scheme 1, chlorodebromination (to give 29) and chloro-
denitration (to give 31) are competitive. Conversion of 31 into 30 is
slower than that of 29 into 30 under the employed conditions (Table
3, entries 1 and 2). The starting material 35 decreased rapidly during
1–3 h, and the reactions completed after 4 h to give the final product
30 in good yield (Fig. 1). No decreasing of the substrate occurred in
the initial 1 h. It may be the inductive period to generate the active
species for the chlorination. During the reactions, a small amount of
29 was detected by 1H NMR spectroscopy and T.L.C., indicating that
transformation of 35 to 29 is faster than that of 29 to 30. On the
NO2
Cl
F
F
4d
(0)
Cl
Cl
Br
Br
5
(0)
NO2
Cl
30
(93)
35
36
CH3
CH2Cl
CH3
+
6e
(70)
route A Cl
NO2
NO2
Cl
37 (21)
38 (3)
CH2Cl
Br
CHCl2
CH3
CH3
Br
Cl
Cl
NO2
Br
+
+
29
7
(14)
Br
Cl
Br
40 (27)
41 (23)
39
38 (24)
NO 2
a
Reagents and conditions: Substrates 4.0 mmol, CC14 15 mL, temp 250 ꢀC, time
7 h, N2.
30
35
The yields were calculated on the basis of the peak of 1,4-dioxane using 1H NMR
b
Cl
spectroscopy.
c
31
Time 21 h.
Time 14 h.
route B
d
e
Temp 240 ꢀC.
Scheme 1. Reaction pathway of the chlorination of 35.

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K. Tanemura et al. / Tetrahedron 66 (2010) 2881–2888
other hand, compound 31 was not detected, indicating that trans-
formation of 35 to 31 is slower than that of 31 to 30. (Table 4). These
results suggest that route A is the main process of the trans-
formation of 35 to 30. It was reported that small amounts of the
rearrangement products, 1,2,4-trichlorobenzene and 1-chloro-2-
bromo-4-nitrobenzene were produced by the photo-induced chlo-
rination of 35 via ipso intermediates, and 1,2,4-trichlorobenzene was
yielded by the photochemical chlorination of 29.16,17
benzoate (45) (28%) (entry 3). Chlorination occurred at the methyl
groups for the reactions of anisole and thioanisole (entries 4 and 5).
Benzotrifuluoride (51) and benzotrichloride (52) were inert under
the employed conditions (entries 6 and 7).
The results for the chlorination of ketones were shown in Table 6.
Chlorination was not observed at the methyl groups or proceeded
Table 6
a
The displacement of the nitro and bromo groups of compounds
36 and 39 was accompanied by the chlorination at the methyl
groups (Table 3, entries 6 and 7).
The reactions of ketones and 1,3-dicarbonyl compounds in high temperature CCl4
Entry
1
Substrate
Products (Yield (%)b)
Recovery (%)b
O
The transformation of other substituents on the benzene ring was
investigated. The results were shown in Table 5. The reaction of
benzaldehyde (42) gave not only benzoyl chloride (43) (64%) but also
a small amount of chlorobenzene (25) (15%) (entry 1). It was reported
that photochemical chlorination18 and the use of sulfuryl chloride-
BPO19 extensively afforded benzoyl chloride 43, while gas-phase
chlorination of benzaldehyde (42) at 375 ꢀC gave chlorobenzene
(25) in a low yield (<10%) together with a large amount of carbon,
probably through intermediate benzoyl and phenyl radicals.10 Re-
actions under subcritical conditions are milder than gas-phase re-
actions,1 so that decomposition to carbon was suppressed. Benzoyl
chloride (43) was stable under the employed conditions, indicating
that intermediacy of 43 for the conversion of benzaldehyde (42) into
chlorobenzene (25) was ruled out (entry 2). The reaction of methyl
benzoate (44) gave benzoyl chloride (43) (26%) and chloromethyl
N.R.e
(76)
H3C
Ph
CH3
CH3
53
O
2
3
N.R.e
(89)
(56)
54
O
O
H3C
CHCl CH3
H3C
CH2CH3
56
55
(21)
O
O
4
(51)
(H3C)2HC
CH3
(H3C)2ClC
CH3
Table 5
a
58 (30)
57
The reactions of various aromatic hydrocarbons in high temperature CCl4
Entry
Substrate
Products (Yield (%)b)
Recovery (%)b
O
O
CHO
COCl Cl
5
6
7
8
N.R.e
N.R.e
N.R.e
(78)
(77)
(82)
(25)
1
(19)
59
42
43 (64)c
25 (15)c
O
O
COCl
OEt
2
3
4
5
6
N.R.d
(95)
(30)
(27)
(26)
(94)
(92)
60
43
COOEt
COOEt
H2C
COCl
COOCH2Cl
COOMe
61
44
45 (28)
43 (26)
O
O
f
OCH2Cl
OMe
–
62
46
47 (71)
9c
–
(77)
(87)
f
10d
N.R.e
SMe
SCH2Cl
SCHCl2
O
O
48
49 (54)
50 (18)
11
N.R.e
(86)
(83)
OEt
CF3
63
N.R.d
51
COOEt
12
N.R.e
CCl3
COOEt
7
N.R.d
64
a
Reagents and conditions: Substrates 4.0 mmol, CCl4 15 mL, temp 250 ꢀC, time
52
7 h, N2.
b
The yields were calculated on the basis of the peak of 1,4-dioxane using 1H NMR
a
Reagents and conditions: Substrates 4.0 mmol, CCI4 15 mL, temp 250 ꢀC, time
spectroscopy.
7 h.
c
Temp 240 ꢀC.
b
Isolated yields.
d
e
f
Temp 230 ꢀC.
No reaction.
Polymeric materials were obtained.
c
The yields were calculated on the basis of the peak of 1,4-dioxane using 1H NMR
spectroscopy.
d
No reaction.

K. Tanemura et al. / Tetrahedron 66 (2010) 2881–2888
2885
quite slowly at the methylene and methine groups (entries 1–4).
Surprisingly, even in the cases of the 1,3-dicarbonyl compounds,
which are more active than simple ketones, reactions did not occur
at the activated methylene groups (entries 5–7). It has been reported
that these ketones involving 1,3-dicarbonyl compounds were easily
chlorinated by the traditional methods such as photo-induced
chlorination20 and the use of sulfuryl chloride4 via the ionic mech-
anism. Even in the cases of more active 2-methyl-substituted-1,3-
dicarbonyl compounds 62–64, chlorination did not observed, al-
though the reaction of 62 gave polymeric materials above 240 ꢀC
(entries 8–12).
Sulfones were stable under the employed conditions and most
of the starting materials were recovered (entries 1–4 in Table 7). A
small amount of chlorobenzene (25) was obtained by aromatic
substitution from the reactions of sulfones 68 and 69 in 5 and 8%
yields, respectively (entries 3 and 4). Benzenesulfonyl chloride and
methanesulfonyl chloride were not detected from the reactions of
compounds 68 and 69, respectively. On the other hand, benzene-
sulfonyl chloride (70) reacted smoothly to yield chlorobenzene (25)
in 84% yield (entry 5). It was reported that chlorobenzene (25) was
easily produced by photochemical chlorination of diphenyl sulfone
(68) and benzenesulfonyl chloride (70) in quantitative yields.11,13
In contrast to the less reactivities of sulfones, sulfoxides were
reduced to sulfides in a low to modest yields together with large
amounts of unidentified complex (entries 6–9). Dibutyl sulfoxide
(71), tetramethylene sulfoxide (73), and diphenyl sulfoxide (75)
were converted into the corresponding sulfides 72, 74, and 76 in 61,
24, and 59% yields, respectively (entries 6–8). Chloromethyl phenyl
sulfide (49) and dichloromethyl phenyl sulfide (50) were isolated
from the reaction of sulfoxide 77 in 15 and 11% yields, respectively
(entry 9). Reduction of sulfoxides to sulfides with Br2–HBr system
has been reported by Oae, although diphenyl sulfoxide 75 was re-
covered quantitatively.21
As for the chlorination of alkyl groups adjacent to the functional
groups listed in Tables 5–7, the reactions proceeded more easily for
anisole and thioanisole, which possess electron-donative oxygen
and sulfur atoms, respectively (Table 5, entries 4 and 5). On the
other hand, the reactions were quite slow for ketones and sulfones,
which have electron-withdrawing carbonyl and sulfonyl groups
(Table 6, entries 1–7,11, and 12, and Table 7, entries 1,2, and 4).
Finally, the reactions of olefins were explored. The results are
summarized in Table 8. Interestingly, the coupling adducts 79, 81,
and 83 between olefins and carbon tetrachloride were obtained
(entries 1–3), although the yield of compound 81 was low (12%)
because of the production of unidentified complex mixtures. The
observed regioselectivities show that the trichloromethyl radical
was introduced into olefins first. Compounds 8122 and 83 were
obtained as a mixture (1:1) and (2:1) of anti/syn isomers, re-
spectively (entries 2 and 3). The starting material was recovered
quantitatively in the case of stilbene (84) (entry 4). Because of the
steric hindrance between the trichloromethyl radical and the
phenyl group on stilbene, the formation of the coupling adduct
might be restricted. It was reported that photo-induced chlorina-
tion3 and the use of sulfuryl chloride-BPO4 resulted in the addition
of Cl2 to the olefinic double bond via radical mechanisms. The BPO-
Table 7
a
The reactions of sulfones and sulfoxides in high temperature CCl4
Entry
1
Substrate
CH3CH2SO2CH2CH3
65
Products (Yield (%)b)
Recovery (%)b
(87)
CH3CH2SO2CHCH3
Cl
66 (3)
2
3
N.R.e
(92)
(94)
S
O2
67
Cl
SO2Ph
25 (5)f
68
SO2Me
Cl
4
(87)
(9)
25 (8)f
69
Cl
SO2Cl
induced addition of sulfuryl chloride to 1-alkenes, which affords b-
chloro-n-alkyl sulfones has been reported by Kharasch and Zavist.23
5
25 (84)f
70
6c
(nBu)2SO
(nBu)2S
(0)
(0)
Table 8
a
71
72 (61)f.g
The reactions of various olefins in high temperature CCl4
Entry
1
Substrate
Time(h)
Products (Yield (%)b)
Recovery (%)b
(0)
d
7
S
S
Cl
74 (24)f, g
O
73
n-Octyl
n-Octyl
CCl3
8
SOPh
SPh
78
79
(81)
8
(0)
(0)
Cl
n-Bu
76 (59)g
n-Bu
n-Bu
CCl3
75
2
3
7
7
8
(21)
(5)
n-Bu
80
SCH2Cl
SCHCl2
81 (12)c
SOCH3
9
Cl
Ph
49 (15)g
50 (11)g
Ph
77
82
CCl3
83 (74)
a
Reagents and conditions: Substrates 4.0 mmol, CCl4, 15 mL, temp 250 ꢀC, time
7 h, N2.
Cl
b
c
d
e
f
Isolated yields.
Ph
Ph
Ph
Temp 220 ꢀC.
4
(98)
Ph
Temp 200 ꢀC.
No reaction.
84
Cl
85 (2)
The yields were calculated on the basis of the peak of 1,4-dioxane using 1H NMR
a
Reagents and conditions: Substrates 4.0 mmol, CC14 15 mL, temp 250 ꢀC, N2.
Isolated yields.
b
c
spectroscopy.
g
Complex mixture was obtained.
Complex mixture was obtained.

2886
K. Tanemura et al. / Tetrahedron 66 (2010) 2881–2888
Table 9
products via the free-radical chain mechanism, while the addition of
a
The reactions of various olefins in high temperature CHCl3
chloro and trichloromethyl radicals to olefins leads to the coupling
adducts. Chloroform, which was generated by the abstraction of the
hydrogen atom of the trichloromethyl radical from the substrate, was
detected by GC–MS spectroscopy in the chloronation of adamantane.
In spite of the considerable stability of carbon tetrachloride at higher
temperature (ca. 500 ꢀC),25 the cleavage of the C–Cl bond occurred
more easily under subcritical conditions. The methods to generate
the trichloromethyl radical via the cleavage of carbon tetrachloride
promoted by Fe26 and ruthenium complexes27 have been reported.
Entry
1
Substrate
Time (h)
Products (Yield (%)b)
dc
Recovery (%)b
(62)
n-Octyl
7
78
Cl
n-Bu
n-Bu
n-Bu
2
3
7
7
7
(81)
(34)
(99)
n-Bu
80
Cl
86
(6)
Ph
Ph
CCl4
+
CCl3
Cl
Cl
87 (34)
82
Cl
Ph
Ph
Ph
4
Ph
84
Cl3C CCl3
Cl
Cl2
85 (trace)
a
Reagents and conditions: Substrates 4.0 mmol, CCl4 15 mL, temp 250 ꢀC, N2.
Isolated yields.
Complex mixture was obtained.
Scheme 2. Mechanism of the decomposition of CCl4.
b
c
3. Conclusions
In conclusion, we carried out the chlorination of aliphatic hydro-
carbons and side chains of aromatic hydrocarbons in subcritical car-
bon tetrachloride. In addition, the reactions of a variety of aromatic
compounds including 1,4-disubstituted benzenes were examined.
The rearranged products were not detected from the reactions of 1,4-
disubstituted benzenes. Interestingly, strongly radicalic atmosphere
was formed for the chlorination of benzaldehyde, ketones, and sul-
fones. The addition of carbon tetrachloride to olefins is the charac-
teristic reaction under high temperature conditions.
The results of the reactions of olefins 78, 80, 82, and 84 in
subcritical chloroform were summarized in Table 9. The reactions in
subcritical chloroform proceeded more slowly than in carbon tet-
rachloride, and the reactions gave different results depending on
the structure of olefins. The reaction of compound 78 gave only
unidentified complex mixture (entry 1). Most of the starting ma-
terials were recovered in the cases of 80 and 84 (entries 2 and 4).
The adduct 87 between the olefin and HCl was obtained by the
chlorination of 82 (entry 3). The results for the chlorination of
olefins 78, 80, 82, and 84 in subcritical dichloromethane were
shown in Table 10. These olefins were stable under the employed
conditions except 78, which was transformed to unidentified
complex mixture.
4. Experimental
4.1. General methods
IR spectra were recorded on a Hitachi I-3000 spectrophotome-
ter. 1H and 13C NMR spectra were measured on a Varian plus-500 W
or a Hitachi R-1200 spectrometer using tetramethylsilane as an
internal standard. Column chromatography was performed on
Wakogel C-200. The Teflon-lined stainless autoclave was purchased
from OM Lab-Tech Co. Ltd., Japan. Carbon tetrachloride was
refluxed with P2O5 and distilled prior to use. Compounds 41,29 47,30
66,31 and 8623 were identified by comparison of their spectroscopic
behaviors with those of authentic samples. All products obtained in
this study otherwise mentioned were completely characterized by
comparison with commercially available samples. Hexachloroeth-
ane and chloroform in the reaction mixture were identified by
comparison of their GC–MS spectra with those of commercially
available samples. Detection of Cl2 was carried out by the ION SE-
LECTIVE PACK TEST kit, WAK-CIO/DP (Kyoritsu Chemical-Check Lab.
Corp.), which DPD (diethyl-p-phenylenediamine) was employed as
a detection agent, or the test paper, Nissan Aqua Check LC, which
syringaldazine (3,5-dimethoxy-4-hydroxybenzaldazine) was ap-
plied (perchased from AS ONE Co.).
Table 10
a
The reactions of various olefins in high temperature CH2Cl2
Entry
1
Substrate
Time (h)
Products (Yield (%)b)
Recovery (%)b
(63)
n-Octyl
7
dc
78
n-Bu
n-Bu
2
3
7
7
7
N.R.d
N.R.d
N.R.d
(83)
(93)
(93)
80
Ph
82
Ph
Ph
4
84
a
Reagents and conditions: Substrates 4.0 mmol, CC14 15 mL, temp 250 ꢀC, N2.
Isolated yields.
Complex mixture was obtained.
No reaction.
b
c
d
4.2. A typical experimental procedure
During the reactions, a large amount of Cl2 was evolved, which
was detected by DPD (diethyl-p-phenylenediamine) and syringal-
dazine (3,5-dimethoxy-4-hydroxybenzaldazine) methods. The plau-
sible mechanism for the formation of Cl2 was shown in Scheme 2.
Thermal cleavage of the C–Cl bond of carbon tetrachloride would
afford the chloro radical and the trichloromethyl radical. Coupling of
the chloro radical gives Cl2. Dimerization of the trichloromethyl
radical probably leads to hexachloroethane.24 Hexachloroethane was
detected by GC–MS spectroscopy in the reaction of carbon tetra-
chloride at 250 ꢀC for 7 h. The resulting chloro radical would react
with the aliphatic and aromatic substrates to give the chlorinated
A mixture of adamantane (1) (4.0 mmol) and carbon tetrachlo-
ride (15 mL) in a 28 mL Teflon-lined stainless autoclave was heated
at 250 ꢀC under nitrogen. The internal pressure reached ca. 7 MPa.
The mixture was heated at the same temperature for 4 h. After
cooling, the solution was washed with water, dried and evaporated.
The residue was chromatographed (hexane) on silica gel to give 2,
3, and 4 in 52, 9, and 3% yields, respectively. Compound 1 was re-
covered in 15% (Table 1, entry 1).
Caution!: Attention should be paid for the leak of the gas since
a large amount of harmful chlorine was evolved during the

K. Tanemura et al. / Tetrahedron 66 (2010) 2881–2888
2887
reactions. It is important to firmly tighten the screw of the stainless
103.2 (s), 126.8 (Canti, d) 127.9 (Csyn, d), 128.2 (Canti, d), 128.6 (Canti,
autoclave. The operation should be carried out in an well-ventilated
fume hood when the autoclave was opened. Many times use of the
stainless autoclave should be avoided because of the rust caused by
chlorine gas. The authors recommend these reactions not for syn-
thetic methods of chlorination, but for investigations of subcritical
chemistry because this method is dangerous.
d), 128.7 (Csyn, d), 129.3 (Csyn, d), 136.7 (Csyn, s), 140.6 (Canti, s). Anal.
Calcd for C10H10Cl4: C, 44.16; H, 3.71. Found: C, 44.40; H, 3.73.
4.3. A typical experimental procedure for the determination
of the yields by 1H NMR spectroscopy
A mixture of toluene (12) (4.0 mmol) and carbon tetrachloride
(15 mL) in a 28 mL Teflon-lined stainless autoclave was heated at
250 ꢀC for 7 h under nitrogen. After cooling, the yield of benzyl
chloride (13) was calculated on the basis of the peak of 1,4-dioxane
using 1H NMR spectroscopy (Table 1, entry 8).
4.2.1. Isolation of triphenylmethyl chloride (17). A mixture of tri-
phenylmethane (16) (4.0 mmol) and carbon tetrachloride (15 mL) in
a 28 mL Teflon-lined stainless autoclave was heated at 250 ꢀC for 7 h
under nitrogen. After cooling, the solution was evaporated at room
temperatureunderreducedpressuretogivetriphenylmethylchloride
17 in 99% yield. (Table 1, entry 10). Colorless solid, mp 111–112 ꢀC
(benzene) (lit.,28 111–112 ꢀC). Chloride 17 was converted into triphe-
nylmethanol quantitatively by the treatmentof the solution of carbon
tetrachloride with water or column chromatography on silica gel.
4.4. Determination of the yields of the products for the
chlorination of 35
A mixture of toluene (35) (4.0 mmol) and carbon tetrachloride
(15 mL) in a 28 mL Teflon-lined stainless autoclave was heated at
250 ꢀC under nitrogen. After 1.0, 2.0, 2.5, 3.0, 4.0, 5.0, and 7.0 h, the
autoclavethe was cooled and the yields of the products were cal-
culated on the basis of the peak of 1,4-dioxane using 1H NMR
spectroscopy (Table 4).
4.2.2. 1-(4-Chloromethylphenyl)adamantane (22). Colorless nee-
dles, mp 92–94 ꢀC (from acetone); IR (KBr) nmax 3440, 2920, 2856,
1518,1452,1384,1344,1332,1320,1310,1286,1118,1104,1032,1016,
968, 864, 840, 800, 724, 534 cmꢁ1 1H NMR (CDCl3)
; d 1.70–2.35
(15H, m, CH, and CH2), 4.50 (2H, s, CH2Cl), 7.35 (2H, d, J¼8.7 Hz,
ArH), 7.38 (2H, d, J¼8.7 Hz, ArH); 13C NMR (CDCl3)
d 28.9 (d), 36.1
Acknowledgements
(s), 36.7 (t), 43.1 (t), 46.2 (t), 125.3 (d), 128.4 (d), 134.5 (s), 151.7 (s).
Anal. Calcd for C17H21Cl: C, 78.29; H, 8.12. Found: C, 78.41; H, 8.10.
We thank Nitto Analytical Techno Center for the analyses of GC–
MS. We thank the Research Promotion Grant (NDUF-08-15) from
Nippon Dental University.
4.2.3. 1-Chloro-3-p-tolyladamantane (23). Colorless needles, mp
69–71 ꢀC (from acetone); IR (KBr) nmax 3448, 2908, 2848,1614,1516,
1448,1414,1342,1272,1102,1034,1018, 976, 842, 832, 804, 744, 692,
672, 536 cmꢁ1; 1H NMR (CDCl3)
d
1.54–2.28 (14H, m, CH, and CH2),
2.32 (3H, s, CH3), 7.14 (2H, d, J¼8.9 Hz, ArH), 7.23 (2H, d, J¼8.9 Hz,
ArH); 13C NMR (CDCl3)
20.9 (q), 31.9 (d), 34.7 (t), 40.2 (s), 41.4 (t),
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d
0.89 (3H, t, J¼6.6 Hz, CH3), 1.10–1.70 (12H, m,
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;
NMR (CDCl3)
d
0.93 (6H, t, J¼6.6 Hz, CH3), 1.20–2.30 (12H, m, CH2),
2.55 (1Hsyn, td, J¼4.6 and 1.0 Hz, CHCCl3), 2.90–3.15 (1Hanti, m,
CHCCl3), 4.64 (1H, td, J¼6.3 and 1.6 Hz, CHCl); 13C NMR (CDCl3)
d
13.8 (q), 13.9 (q), 22.0 (t), 22.9 (t), 27.5 (Canti, t), 28.5 (Csyn, t), 29.0
(Csyn, t), 29.4 (Canti, t), 31.8 (Canti, t), 32.2 (Csyn, t), 32.7 (Canti, t), 39.0
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12.2 (Csyn, q), 60.8 (Canti, d), 61.2 (Csyn, d), 61.9 (Csyn, d), 62.1 (Canti, d),

2888
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