Rhenium complex-catalyzed acylative cleavage of ethers with acyl chlorides

Article abstract of DOI:10.1016/j.tet.2011.07.072

It was found that rhenium complex was an efficient catalyst for the acylative cleavage of C-O bond of ethers with acyl chlorides. When acyclic ethers were allowed to react with acyl chlorides in the presence of a catalytic amount of ReBr(CO)₅, acylative cleavage of C-O bond of acyclic ethers smoothly proceeded to give the corresponding esters in moderate to good yields. Similarly, cyclic ethers were acylative cleaved by acyl chlorides to give the corresponding chloro substituted esters in good yields by the use of Re ₂O₇ catalyst.

Full text of DOI:10.1016/j.tet.2011.07.072

Tetrahedron 67 (2011) 7217e7221
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Rhenium complex-catalyzed acylative cleavage of ethers with acyl chlorides
*
Rui Umeda, Takashi Nishimura, Kenta Kaiba, Toshimasa Tanaka, Yuuki Takahashi, Yutaka Nishiyama
Department of Chemistry and Material Engineering, Faculty of Chemistry, Material and Bioengineering, Kansai University, Suita, Osaka 564-8680, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 May 2011
Received in revised form 22 July 2011
Accepted 22 July 2011
Available online 29 July 2011
It was found that rhenium complex was an efficient catalyst for the acylative cleavage of CeO bond of
ethers with acyl chlorides. When acyclic ethers were allowed to react with acyl chlorides in the presence
of a catalytic amount of ReBr(CO)5, acylative cleavage of CeO bond of acyclic ethers smoothly proceeded
to give the corresponding esters in moderate to good yields. Similarly, cyclic ethers were acylative
cleaved by acyl chlorides to give the corresponding chloro substituted esters in good yields by the use of
Re2O7 catalyst.
Keywords:
Rhenium complex
Ethers
Ó 2011 Elsevier Ltd. All rights reserved.
Esters
Acylation
Catalysis
1. Introduction
2. Results and discussion
The cleavage of a CeO bond of ethers is a versatile reaction in
organic synthesis and many methods have been developed.1
Among them, the acylative cleavage of ethers with acyl chlorides
is one of the attractive methods for the preparation of esters. Thus,
it is of great interest in the development of the convenient and
practical catalytic methods for the transformation of ethers into
esters. There are some reports on the acylative cleavage of ethers
with acyl chlorides using Lewis acids,2 groups 5 and 6 transition
metal complexes3 and metals, such as Al4 and Zn,5 Pt,6 and iodine.7
However, these methods involved some disadvantages, such as the
use of toxic, expensive, and unstable reagents or catalysts, the
formation of mixture of products, and low yields of products.
Recently, Narasaka and our groups have shown the hitherto
unknown capacity of ReBr(CO)5, which is a relatively air-stable and
water-tolerant compound, as an efficient catalyst for the various
carbonecarbon formation.8,9 During the course of our study on the
catalytic use of the rhenium complex, it was found that the
ReBr(CO)5 complex acts as the catalyst on the acylative cleavage of
the CeO bond of ethers with acyl chlorides giving the corre-
sponding esters in moderate to good yields.8f Here, we would like
to report the full results on the rhenium complex-catalyzed acy-
lative cleavage of the CeO bond of acyclic and cyclic ethers with
acyl chlorides.
2.1. Rhenium-catalyzed reaction of acylic ethers with acyl
chlorides
To determine the optimized reaction conditions, diisopropyl
ether (1a) was treated with benzoyl chloride (2a) in the presence of
a catalytic amount of rhenium complex under various reaction
conditions and these results are shown in Table 1. When 1a was
allowed to react with 2a in the presence of a catalytic amount of
ReBr(CO)5 (2.5 mol %) at 80 ꢀC for 2 h in 1,2-dichloroethane solvent,
the acylative cleavage of CeO bond of 1a smoothly proceeded to
give isopropyl benzoate (3a) in 90% yield (entry 4 in Table 1). The
acylated product, 3a, was not obtained when the reaction was
carried out without rhenium complex or with lower reaction
temperatures (25 ꢀC and 60 ꢀC) (entries 1e3). Even when the
amount of ReBr(CO)5 used as a catalyst was decreased; ester 3a was
obtained in 87% yield (entry 5). Although acylative cleavage of 1a
with 2a was occurred, even using hexane and benzene instead of
dichloroethane as the solvent, the best yield was obtained in di-
chloroethane solvent (entries 4, 6, and 7). The use of coordinating
solvent, such as acetonitrile caused a distinct decrease in the yield
of 3a (entry 8). The other rhenium complexes, ReCl(CO)5, Re2(CO)10
CH3ReO3, ReCl5, and Re2O7, also functioned as a catalyst; however,
the yields of 3a slightly decreased (entries 9e13).
,
The reaction of diisopropyl ether (1a) and various acyl and aroyl
chlorides 2 was carried out under the same reaction conditions as
entry 4 in Table 1, and these results are shown in Table 2. The
acylative cleavage of 1a with various aroyl chlorides having
* Corresponding author. Tel.: þ81 6 6368 0902; fax: þ81 6 6339 4026; e-mail
address: nishiya@kansai-u.ac.jp (Y. Nishiyama).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.07.072

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R. Umeda et al. / Tetrahedron 67 (2011) 7217e7221
Table 1
Table 2
Rhenium-catalyzed reaction of diisopropyl ether (1a) with benzoyl chloride (2a)
Rhenium-catalyzed reaction of diisopropyl ether (1a) with acyl chlorides 2a
under various reaction conditionsa
cat.ReBr(CO)5
ClCH2CH2Cl
O
O
O
+
O
O
i-C3H7
cat.Re complex
solvent, temp.
i-C3H7
i-C3H7
R
Cl
R
O
3
O
i-C3H7
i-C3H7
Cl
Oi-C3H7
+
1a
2
Yieldb (%)
1a
2a
3a
Entry
Acyl chloride
Product
O
O
Entry
Re complex
Solvent
Temp (ꢀC)
Yieldb (%)
i-C3H7
Cl
O
1
2
3
None
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
C6H14
80
25
60
80
80
80
80
80
80
80
80
80
80
0
0
ReBr(CO)5
ReBr(CO)5
ReBr(CO)5
ReBr(CO)5
ReBr(CO)5
ReBr(CO)5
ReBr(CO)5
ReCl(CO)5
Re2(CO)10
CH3ReO3
ReCl5
R
R
R¼H
Trace
90 (76)
87
81
89
0
74
72
84
1
3a
3b
3c
3d
3e
3f
76
66
56
41
87
93
0
2c
3c
4c
5
4-CH3
3-CH3
2-CH3
4-OCH3
4-Cl
4
5c
6
7
8
9
10
11
12
13
C6H6
CH3CN
6
7
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
4-NO2
3g
O
O
69
80
8
3h
3i
77
72
i-C3H7
i-C3H7
Re2O7
C7H15
C4H9
Cl
C7H15
C4H9
O
a
Reaction condition: 1a (0.6 mmol), 2a (0.5 mmol), rhenium complex (2.5 mol %),
O
O
and solvent (3.0 mL) for 2 h.
9d
b
Cl
O
Yields were determined by GC based on 2a. The number in parenthesis shows
C2H5
C2H5
the isolated yield.
c
ReBr(CO)5 (1.0 mol %) was used.
O
O
C5H11
C2H5
C5H11
C2H5
i-C3H7
10
3j
0
Cl
C2H5
O
C2H5
electron donating groups and halogen atom on aromatic ring pro-
ceeded to give the corresponding esters, 3b,e,f, in moderate to good
yields (entries 2, 5, and 6). For the reaction of 2- and 3-
methylbenzoyl chloride, the yields of esters, 3c,d, were slightly
decreased (entries 3 and 4). In contrast, in the case of 4-
nitrobenzoyl chloride substituted an electron withdrawing group,
isopropyl 4-nitrobenzoate (3g) was not formed (entry 7). For the
reaction, there is no significant reactivity difference between the
aroyl and acyl chlorides. The reaction of 1a with octanoyl chloride
and 2-ethylhexanoyl chloride proceeded to give the esters 3h,i in
77 and 72% yields, respectively (entries 8 and 9). When the 2,2-
a
Reaction condition: 1a (0.6 mmol), 2 (0.5 mmol), ReBr(CO)5 (2.5 mol %), and
ClCH2CH2Cl (3.0 mL) at 80 ꢀC for 2 h.
b
Isolated yields based on 2.
c
For 12 h.
For 9 h.
d
Table 3
Rhenium-catalyzed reaction of ether 1 with benzoyl chloride (2a)a
O
O
cat.ReBr(CO)5
ClCH2CH2Cl
O
R1
R2
Cl
diethylheptanoyl chloride, which have
a sterically hindered
OR1
+
group, was used as an acyl chloride, no acylative cleavage product
3j was formed (entry 10).
1
2a
3
The representative results for the reaction of various ethers 1
with benzoyl chloride (2a) are shown in Table 3. For the reaction
of dioctyl ether with 2a, the yield of octyl benzoate (3k) was only
8% yield, however, the yield of the 3k was improved by extending
the reaction time and increasing the amount of the catalyst (entry
2). Allyl benzoate (3l) was formed by the reaction of diallyl ether
with 2a, in 68% yield (entry 3). For the reaction of dibenzyl ether,
various complicated products including aromatic ketones, Frie-
deleCrafts acylation products, were formed (entry 4). For the re-
action of the unsymmetric ethers, such as tert- and sec-butyl
methyl ether and tert- and sec-butyl ethyl ether, it is interesting to
note that the CeO bond of these ethers was selectively cleaved to
give methyl and ethyl benzoate, 3n and 3o, in 66, 43, 65, and 75%
yields, respectively (entries 5, 6, 8, and 9). In the case of n-butyl
methyl ether, methyl benzoate (3n) was formed in low yield (27%)
together with the formation of n-butyl benzoate (5%) under
the longer reaction time and increasing the catalyst loading
conditions.
Entry
R1
R2
Product
Yieldb (%)
1
i-C3H7
C8H17
CH2]CHCH2
PhCH2
CH3
CH3
CH3
C2H5
C2H5
i-C3H7
C8H17
CH2]CHCH2
PhCH2
t-C4H9
s-C4H9
C4H9
t-C4H9
3a
3k
3l
3m
3n
3n
3n
3o
3o
76
35
68
Trace
66
2c,d
3
4
5
6
43
7d,e
8
27f
65
9
s-C4H9
75
a
Reaction condition: 1 (0.6 mmol), 2a (0.5 mmol), ReBr(CO)5 (2.5 mol %), and
ClCH2CH2Cl (3.0 mL) at 80 ꢀC for 2 h.
b
Isolated yields based on 2a.
For 5 h.
ReBr(CO)5 (12.5 mol %) was used.
c
d
e
For 20 h.
f
1H NMR yield. n-Butyl benzoate (5%) was also formed.
amount of ReBr(CO)5 in 1,2-dichloroethane solvent, acylative
cleavage of CeO bond of 4 with 2a smoothly proceeded to give 4-
chlorobutyl benzoate (5a) in 76% yield along with the formation
of a small amount of 4-chlorobutoxy butyl benzoate (6a), 1:2 cou-
pling product of 2a and 4 (entry 1). In order to improve the yield of
5a, 2a was allowed to react with 4 using the other rhenium com-
plexes instead of ReBr(CO)5. In the contrast to that of acyclic ethers,
2.2. Rhenium-catalyzed reaction of cyclic ethers with acyl
chlorides
Next, we examined the acylative cleavage of CeO bond of cyclic
ethers with benzoyl chloride (2a) (Table 4). When 2a was allowed
to react with tetrahydrofuran (THF) (4) in the presence of a catalytic

R. Umeda et al. / Tetrahedron 67 (2011) 7217e7221
7219
Table 5
the best yield was observed by the use of Re2O7 as the catalyst
(entries 4e6 and 9).
Rhenium-catalyzed reaction of THF (4) with acyl chlorides 1a
cat.Re2O7
O
O
+
Table 4
Cl
O
R
Cl
Metal complex-catalyzed reaction of THF (4) with benzoyl chloride (2a)a
R
O
ClCH2CH2Cl
4
1
5
O
Cl
cat.Metal complex
ClCH2CH2Cl
Yieldb (%)
O
Ph
O
O
5a
Entry
Acyl chloride 1
Product 5
+
O
O
Ph
Cl
O
4
+
O
Cl
2a
Cl
O
O
Ph
Cl
R
R
6a
1
2
3
4
5
6
7
R¼H
5a
92
85
90
78
65
69
0
4-CH3
3-CH3
2-CH3
4-OCH3
4-Cl
5b
5c
5d
5e
5f
Entry
Metal
THF (4) (mmol)
Yieldb (%)
complex
5a
6a
1
2
3
4
5
6
7
8
ReBr(CO)5
ReBr(CO)5
ReBr(CO)5
ReCl(CO)5
CH3ReO3
Re2O7
0.5
1.2
3.0
0.5
0.5
0.5
1.2
3.0
0.5
1.2
3.0
1.2
3.0
1.2
3.0
1.2
3.0
1.2
3.0
76
45
52
86
90
97 (92)
82
69
17
44
30
7
1
27
38
0
0
2
4-NO2
5g
O
O
8
9
5h
5i
78
83
Cl
Cl
C7H15
C4H9
Cl
C7H15
C4H9
O
Re2O7
Re2O7
8
O
O
14
14
26
32
9
Re2(CO)10
Re2(CO)10
Re2(CO)10
MnBr(CO)5
MnBr(CO)5
ZnCl2
ZnCl2
FeCl3
FeCl3
BiCl3
Cl
O
10c
11c
12
13
14
15
16
17
18
19
C2H5
C2H5
Trace
26
57
69
21
17
75
71
3
0
0
2
2
14
7
O
O
O
10
5j
66
Cl
Cl
a
Reaction condition:
ClCH2CH2Cl (3.0 mL) at 80 ꢀC for 12 h.
1
(0.6 mmol), 4 (0.5 mmol), Re2O7 (1.3 mol %), and
BiCl3
b
Isolated yields based on 4.
a
Reaction condition: 2a (0.6 mmol), metal complex (2.5 mol % for entries 1e5 and
7e19 and 1.3 mol % for entries 6e11), and ClCH2CH2Cl (3.0 mL) at 80 ꢀC for 12 h.
b
Yields were determined by GC based on 4 for entries 1, 4, 5, 6, and 9 and 2a for
(Eq. 1). In the case of 3-phenyltetrahydrofuran, 4-chloro-3-
phenylbutyl benzoate (5l) was predominantly obtained in 73%
yield along the formation of 4-chloro-2-phenylbutyl benzoate (5l0)
(7%) (Eq. 2). This rhenium complex catalytic system is also effective
for the acylative cleavage of the CeO bond of 3-, 4-, and six-
membered cyclic ethers to give the 2-, 3-, and 5-chloro
substituted esters in 46, 70, and 52% yield, respectively (Eqs. 3e5).
entries 2, 3, 7, 8, and 10e19. The number in parenthesis shows the isolated yield.
c
For 24 h.
It has been reported that the THF (4) was acylative cleaved by
acyl halides in the presence of various Lewis acids giving the cor-
responding 4-chloro substituted esters.2e7 However, to the best of
our knowledge, there are only a few reports on the formation of 1:2
coupling product of acyl halides and 4.3b,10 Thus, in order to im-
prove the selectivity of 6a, THF (4) was treated with benzoyl
chloride (2a) in the presence of various Lewis acids. The selectivity
of 6a was improved by the increasing the amount of 4, when
ReBr(CO)5, Re2O7,11 and Re2(CO)10 were used as a catalyst (entries 2,
3, 7, 8, 10, and 11). The highest yield of 6a was attained by the use of
ReBr(CO)5. The use of MnBr(CO)5 catalyst led to the distinct de-
crease of the yields of both 5a and 6a (entries 12 and 13). In the case
of ZnCl2 and FeCl3, which are often used as a catalyst, the yields of
6a were very low (entries 14e17). In the case of BiCl3 (entries 18 and
19), 6a was obtained in 14% yield when 2.0 equiv amount of 4 was
used.
O
Cl
O
O
cat.Re2O7
5k
+
Cl
+
(eq. 1)
Cl
O
ClCH2CH2Cl
86 %
O
O
5k'
(5k : 5k' = 50 : 1)
The reaction of cyclic ethers with various acyl and aroyl chlo-
rides carried out under the same reaction conditions as that of
entry 6 in Table 4, and the representative results are shown in
Table 5. On the reaction of aroyl chlorides except 4-nitrobenzoyl
chloride, the acylative cleavage of THF (4) efficiently proceeded to
give the corresponding 4-chlorobutyl benzoates 5bef in good to
excellent yields (entries 2e7). Similarly, 4-chloro substituted esters
5hej were obtained by the reaction of 4 with the corresponding
acyl chlorides in moderate to good yields (entries 8e10).
O
Cl
Cl
O
O
5l
cat.Re2O7
(eq. 2)
Cl
+
+
O
ClCH2CH2Cl
80 %
O
O
5l'
On the CeO bond cleavage of 2-methyltetrahydrofuran, the CeO
bond attached to the methyl substituent was predominantly
cleaved to form 2-chloropentyl benzoate (5k) in 86% yield with the
formation of a small amount of 5-chloropentan-2-yl benzoate (5k0)
(5l : 5l' = 10 : 1)

7220
R. Umeda et al. / Tetrahedron 67 (2011) 7217e7221
ethyl propionate with ethyl magnesium bromide followed by the
carboxylation with HCOOH in the presence of sulfonic acid in acetic
acid solution.13 3-Phenyltetrahydrofuran was synthesized by the
intramolecular cyclization of 2-phenyl-1,4-butanadiol, which was
prepared by the reduction of 2-phenylsuccinic acid with LiAlH4.14,15
Other chemical agents were obtained commercially and were pu-
rified if necessary.
O
Cl
O
O
O
cat.Re2O7
7
(eq. 3)
+
Cl
+
O
ClCH2CH2Cl
46 %
O
Cl
7'
4.2. General procedure for rhenium-catalyzed reaction of
acyclic ethers with acyl chlorides
(7 : 7' = 3 : 2)
A
1,2-dichloroethane (3.0 mL) solution of acyl chloride
O
O
O
O
(0.6 mmol), ether (0.5 mmol), and ReBr(CO)5 (2.5 mol %) was stirred
under an atmosphere of nitrogen at 80 ꢀC for 2 h. After the reaction
was complete, H2O was added to the reaction mixture and
extracted with ethyl acetate. The organic layer was dried with
MgSO4. The resulting mixture was filtered, and the filtrate was
concentrated. Purification of the residue by silica gel column
chromatography afforded ester. The structures of the products were
assigned by their 1H and 13C NMR, and mass spectra. The product
was characterized by comparing its spectral data with those of
authentic sample or previous reports 3a,16 3b,17 3c,18 3d,17 3e,17 3f,17
3k,17 3l,3 3n,19 and 3o.19 The structures of the products (3h and 3i)
were assigned by their 1H and 13C NMR, IR, and mass spectrum.
cat.Re2O7
Cl
Cl
+
(eq. 4)
(eq. 5)
Cl
ClCH2CH2Cl
70%
Cl
8
O
O
cat.Re2O7
O
O
Cl
Cl
+
ClCH2CH2Cl
9
52%
For the reaction of dioctyl ether with 1a, the formation of 1- and
2-chlorooctane and 1-octene were identified with GC analysis. In
order to clarify the reaction pathway, a stoichiometric reaction of
dioctyl ether with ReBr(CO)5 was carried out at 80 ꢀC. However, 1-
and 2-chlorooctane and 1-octene were not formed and dioctyl
ether was recovered. The results on the reaction of tert- and sec-
butyl methyl ether, tert- and sec-butyl ethyl ether, and 2-
methyltetrahydrofuran were consistent with the fact that CeO
bond, which gives more stable carbocations species is cleaved.
Narasaka and Kusama have already reported the rhenium complex-
catalyzed the FriedeleCrafts acylation of aromatic compounds
having an electron donating group, such as methoxy and methyl
with acyl chlorides giving the corresponding alkyl aryl ketones.8a In
the manuscript, they suggested that coordinatively unsaturated
complex, ReBr(CO)4, which was generated in situ the decarbon-
ylation of CO coordinated with ReBr(CO)5, acts as a Lewis acid
catalyst.12
From these results, we proposed that the decarbonylation of CO
coordinated with ReBr(CO)5 to form the ReBr(CO)4, was the first
step at the catalytic reaction. Acyl and aroyl chlorides were reacted
with the ReBr(CO)4. The addition of generated species to the oxygen
of ether 2 followed by the elimination of chloride anion produced
the oxonium salt. The cleavage of the carboneoxygen bond of
oxonium salt gave the ester 3. On the other hand, the reaction
pathway including the generation of acyl cation (RCOþ) and aroyl
cation (ArCOþ), which were generated by the reaction of acyl and
aroyl chlorides and ReBr(CO)4, can not be ruled out.
Compound 3h: 1H NMR (270 MHz, CDCl3)
d
4.99 (sept, J¼6.3 Hz,
1H), 2.24 (t, J¼7.6 Hz, 2H), 1.63e1.56 (m, 2H), 1.30e1.20 (m, 14H),
0.86 (t, J¼6.8 Hz, 3H). 13C NMR (68 MHz, CDCl3)
d 173.5, 67.3, 34.7,
31.6, 29.0, 28.9, 25.0, 22.6, 21.8, 14.0. IR (KBr) 2929, 2857, 1735, 1467,
1375, 1178, 1110 cmꢁ1
.
Compound 3i: 1H NMR (270 MHz, CDCl3)
d
5.02 (sept, J¼6.2 Hz,
1H), 2.24e2.14 (m, 1H), 1.68e1.42 (m, 4H), 1.27e1.20 (m, 10H), 0.84
(t, J¼7.3 Hz, 6H). 13C NMR (68 MHz, CDCl3)
d 175.9, 67.1, 47.5, 31.8,
29.5, 25.5, 22.6, 21.8,14.0,11.8. IR (KBr) 2961, 2929, 2858,1731,1462,
1380, 1262, 1180, 1109, 808, 676 cmꢁ1
.
4.3. General procedure for rhenium-catalyzed reaction of
cyclic ethers with acyl chlorides
A
1,2-dichloroethane (3.0 mL) solution of acyl chloride
(0.6 mmol), cyclic ether (0.5 mmol), and Re2O7 (1.3 mol %) was
stirred under an atmosphere of nitrogen at 80 ꢀC for 2 h. After the
reaction was complete, H2O was added to the reaction mixture and
extracted with ethyl acetate. The organic layer was dried with
MgSO4. The resulting mixture was filtered, and the filtrate was
concentrated. Purification of the residue by silica gel column
chromatography afforded ester. The product was characterized by
comparing its spectral data with those of authentic sample or
previous reports 5a,5c 5b,17 5c,2i 5e,17 5f,20 5j,20 5k,21 6,3b 7,22,23
70,22,23 and 9.3 The structures of the products (5d, 5h, 5i, 5l, and
8) were assigned by their 1H and 13C NMR, IR, and mass spectrum.
Compound 5d: 1H NMR (400 MHz, CDCl3)
7.37e7.26 (m, 2H), 4.35 (t, J¼6.0 Hz, 2H), 3.62 (t, J¼6.2 Hz, 2H), 2.41
(s, 3H), 1.99e1.91(m, 4H). 13C NMR (100 MHz, CDCl3)
166.7, 138.1,
d 7.85e7.82 (m, 2H),
3. Conclusion
d
In summary, we developed a new catalytic method for the
acylative and aroylative cleavage of the CeO bond of ethers with
acyl and aroyl chlorides giving the esters in moderate to good
yields.
133.7, 130.0, 128.2, 127.7, 126.6, 64.0, 44.5, 29.2, 26.1, 21.3. IR (KBr)
2960, 2873, 1783, 1718, 1602, 1575, 1488, 1458, 1383, 1293, 1254,
1142, 1081, 1051, 999, 738, 696, 654 cmꢁ1
.
Compound 5h: 1H NMR (270 MHz, CDCl3)
d
4.08 (t, J¼5.8 Hz, 2H),
3.55 (t, J¼5.9 Hz, 2H), 2.27 (t, J¼7.3 Hz, 2H), 1.86e1.71 (m, 4H), 1.59
(t, J¼7.0 Hz, 2H), 1.86e1.77 (m, 4H), 1.76e1.48 (m, 2H), 1.26 (br, 8H),
4. Experimental section
4.1. Reagents
0.86 (t, J¼6.2 Hz, 3H). 13C NMR (68 MHz, CDCl3)
d 173.8, 63.3, 44.4,
34.2, 31.6, 29.0, 28.8, 26.0, 24.9, 22.5, 14.0 (one signal is missing due
to overlap). IR (KBr) 2928, 2856, 1736, 1462, 1166, 1105 cmꢁ1
.
2-Ethylhexanoyl and 2,2-diethylheptanoyl chlorides were pre-
pared by reaction of thiony chloride with the corresponding acids.
2,2-Diethylheptanoic acid was prepared by the Grignard reaction of
Compound 5i: 1H NMR (270 MHz, CDCl3)
d
4.11 (t, J¼5.8 Hz, 2H),
3.56 (t, J¼6.1 Hz, 2H), 2.30e2.20 (m, 1H), 1.91e1.73 (m, 4H),
1.69e1.38 (m, 4H), 1.36e1.16 (m, 4H), 0.88 (t, J¼7.6 Hz, 6H). 13C NMR

R. Umeda et al. / Tetrahedron 67 (2011) 7217e7221
7221
Yadav, J. S.; Reddy, B. V. S.; Reddy, P. M. K.; Dash, U.; Gupta, M. K. J. Mol. Catal. A:
Chem. 2007, 271, 266; (j) Suresh, V.; Suryakiran, N.; Venkateswarlu, Y. Can. J.
Chem. 2007, 85, 1037; (k) Suresh, V.; Suryakiran, N.; Rajesh, K.; Selvam, J. J. P.;
Srinivasulu, M.; Venkateswarlu, Y. Synth. Commun. 2008, 38, 92.
3. (a) Guo, Q.; Miyaji, T.; Gao, G.; Hara, R.; Takahashi, T. Chem. Commun. 2001,
1018; (b) Guo, Q.; Miyaji, T.; Hara, R.; Shen, B.; Takahashi, T. Tetrahedron 2002,
58, 7327.
4. Luzzio, F. A.; Bobb, R. A. Tetrahedron 1999, 55, 1851.
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1995, 60, 745; (c) Pasha, M. A.; Myint, Y. Y. Ultrason. Sonochem. 2006, 13, 175.
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2005, 46, 8493; (b) Pasha, M. A.; Manjula, K. Synth. Commun. 2007, 37, 927.
8. (a) Kusama, H.; Narasaka, K. Bull. Chem. Soc. Jpn. 1995, 68, 2379; (b) Nishiyama,
Y.; Kakushou, F.; Sonoda, N. Bull. Chem. Soc. Jpn. 2000, 73, 2779; (c) Nishiyama,
Y.; Kakushou, F.; Sonoda, N. Tetrahedron Lett. 2005, 46, 787; (d) Nishiyama, Y.;
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(68 MHz, CDCl3)
22.6, 13.9, 11.8. IR (KBr) 2959, 2873, 1732, 1460, 1171 cmꢁ1
Compound 5l: 1H NMR (270 MHz, CDCl3)
7.98 (d, J¼7.0 Hz, 2H),
7.54e7.24 (m, 8H), 4.53e4.41 (m, 2H), 3.56e3.48 (m,1H), 3.42e3.29
(m, 2H), 2.46e2.05 (m, 2H). 13C NMR (100 MHz, CDCl3)
166.4,
139.9, 133.0, 128.8, 128.4, 127.9, 127.3, 68.3, 42.5, 42.2, 35.3.
Compound 8: 1H NMR (CDCl3, 400 MHz):
8.04e8.01 (m, 2H),
7.61e7.57 (m, 1H), 7.48e7.44 (m, 2H), 4.31 (s, 2H), 3.68e3.62 (m,
4H), 1.22 (s, 3H). 13C NMR (CDCl3, 100 MHz):
165.9, 133.3, 129.5,
129.4, 128.4, 66.7, 48.0, 41.0, 18.8. IR (KBr): 3063, 2975, 1724, 1451,
1272, 1111, 710 cmꢁ1
d 176.4, 63.1, 47.4, 44.4, 31.8, 29.6, 29.2, 26.1, 25.4,
.
d
d
d
d
.
Acknowledgements
This research was supported by a Grant-in-Aid for Science Re-
search, and Strategic Project to Support the Formation of Research
Bases at Private Universities from the Ministry of Education, Culture
Sports, Science and Technology of Japan.
9. Selected papers on using ReBr(CO)5 as catalyst for CeC bond formation, see: (a)
Zuo, W.-X.; Hua, R.; Qiu, X. Synth. Commun. 2004, 34, 3219; (b) Kuninobu, Y.;
Kawata, A.; Takai, K. Org. Lett. 2005, 7, 4823; (c) Zuo, W.-X.; Hua, R. Tetrahedron
Lett. 2007, 63, 11803; (d) Kuninobu, Y.; Yu, P.; Takai, K. Chem. Lett. 2007, 36, 1162.
ꢀ
ꢁꢀ
10. Vícha, R.; Necas, M.; Potacek, M. Collect. Czech. Chem. Commun. 2006, 71, 709.
11. Sinha et al. have reported that Re2O7 catalyzed hetero acylative ring-opening
dimerization of THF with trifluoroacetic anhydride and a carboxylic acid at
room temperature, see: Lo, H. C.; Han, H.; D’Souza, L. J.; Sinha, S. C.; Keinan, E. J.
Am. Chem. Soc. 2007, 129, 1246.
Supplementary data
Supplementary data for new compounds of 1H and 13C NMR
spectra. Supplementary data can be found in the online version, at
doi:10.1016/j.tet.2011.07.072.
12. It has already known that rhenium complexes, such as CH3ReO3 and Re2O7, act
~
€
as Lewis acids. For a related review, see: Romao, C. C.; Kuhn, F. E.; Herrmann,
W. A. Chem. Rev. 1997, 97, 3197.
13. Takahashi, Y.; Yoneda, N. Synth. Commun. 1989, 19, 1945.
14. Gotoh, H.; Masui, R.; Ogino, H.; Shouji, M.; Hayashi, Y. Angew. Chem., Ed. 2006,
45, 6853.
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