Copper-catalyzed Csp3-O cross-coupling of unactivated alkyl halides with organic peroxides

Article abstract of DOI:10.1016/j.tet.2013.11.085

An efficient Cu-catalyzed C_sp3-O coupling of peroxides with haloalkanes is described. High yields of products were achieved under mild conditions. Significantly, in addition to primary alkyl halides, secondary alkyl halogenated hydrocarbons could also be applied to this system. The new reaction system could tolerate a wide range of organic peroxides.

Full text of DOI:10.1016/j.tet.2013.11.085

Tetrahedron 70 (2014) 212e217
Contents lists available at ScienceDirect
Tetrahedron
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Copper-catalyzed Csp3eO cross-coupling of unactivated alkyl halides
with organic peroxides
,
b
,
,
b
,
,
b
,
,b,c
Huan-Huan Chen a c, Guang-Zu Wang a c, Jin Han a c, Meng-Yu Xu a
,
,
b,
,b,c,
*
Yong-Qiang Zhao a c, Hua-Jian Xu a
a School of Chemical Engineering, Hefei University of Technology, Hefei 230009, Anhui Province, PR China
b School of Medical Engineering, Hefei University of Technology, Hefei 230009, Anhui Province, PR China
c Key Laboratory of Advanced Functional Materials and Devices, Hefei 230009, Anhui Province, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
An efficient Cu-catalyzed Csp3eO coupling of peroxides with haloalkanes is described. High yields of
products were achieved under mild conditions. Significantly, in addition to primary alkyl halides, sec-
ondary alkyl halogenated hydrocarbons could also be applied to this system. The new reaction system
could tolerate a wide range of organic peroxides.
Received 18 September 2013
Received in revised form 19 November 2013
Accepted 25 November 2013
Available online 3 December 2013
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Csp3eO coupling
Copper-catalyzed
Organic peroxides
Secondary alkyl halides
Arylealkyl esters
1. Introduction
organic chemistry. As an ongoing research of exploring less ex-
pensive Cu salts for the cross-coupling reactions,5 herein, we report
Arylealkyl esters present a class of useful organic building
blocks, which have been utilized as solvents, lubricants, pesticides,
spices, and medicines.1 In this context, many efforts have been
devoted to the study of the synthesis of arylealkyl esters.2 Among
which, organic peroxides as substrates are the common ones. Or-
ganic peroxides always undergo a free radical process.3 They can be
transformed to the arylealkyl esters by reacting with triethylalu-
minum, alkyl alcohols, and carbonyl compounds.4 Among these
peroxides, benzoic peroxyanhydride is the most widely used. In
1961, Petukhov et al. reported the reactions of triethylaluminum or
triphenylaluminum with benzoyl peroxide in benzene solution to
obtain arylealkyl esters.4a Later, Mitsunobu et al. reported a pro-
tocol for TPP (triphenylphosphine) catalyzed synthesis of
arylealkyl esters by employing benzoyl peroxide and alcohols.4b,4c
an efficient method for the synthesis of arylealkyl esters by cou-
pling of peroxides and haloalkanes with Cu(OAc)2 as catalyst under
mild conditions.
2. Results and discussion
Our study began by examining the cross-coupling of 4-
methoxyphenylacetonitrile with trimethyl(trifluoromethyl)silane.
Unfortunately, the desired product (3,3,3-trifluoro-2-(4-methoxy
phenyl)propanenitrile) was not observed despite many attempts.
However, an unexpected arylealkyl ester was generated by the
reaction of solvent (1,2-dichloroethane) with the oxidant (benzoic
peroxyanhydride) in a high yield. After further exploration, we
found the first Cu-catalyzed Csp3eO cross-coupling of peroxides
with haloalkanes. In our system, both halves of the benzoyl per-
oxide were utilized, which was of good atomic efficiency. Moreover,
unactivated secondary alkyl halogenated hydrocarbons could also
be applied to the system in high yields.
We chose to focus our initial studies on the Csp3eO cross-
coupling of benzoic peroxyanhydride with 1,2-dichloroethane in
the presence of 10% Cu(OAc)2/10% 1,10-phenanthroline at 80 ꢀC for
24 h. The corresponding product was obtained in 82% yield (entry
1). Both catalyst and ligand were crucial for the reaction. The yield
Thereafter, more methods of organocatalytic
a-oxygenation of
carbonyl compounds, which used benzoyl peroxide as benzoyl re-
agents have been reported.4de4k Further development of the re-
ported Csp3eO coupling reactions to use organic peroxides to
synthesize arylealkyl esters has remained important in synthetic
* Corresponding author. Tel.: þ86 551 62904353; fax: þ86 551 62904405; e-mail
address: hjxu@hfut.edu.cn (H.-J. Xu).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.11.085

H.-H. Chen et al. / Tetrahedron 70 (2014) 212e217
213
Table 2
of product could be decreased, respectively, to 6% or 4% without the
Copper-catalyzed cross-coupling of organic peroxides and primary alkyl halides
catalyst or the ligand (entries 2 and 3). Compared with other bases
such as KOtBu, LiOtBu, Na2CO3, and K3PO4, NaOtBu was more fa-
vorable to the reaction conditions (entries 4e7). Significant differ-
ences of the yield of the desired product was observed when other
monovalent copper salts were used as the catalyst such as CuI and
CuSCN, which were inferior to Cu(OAc)2 (entries 8e10). When FeCl3
was used as the catalyst, a trace amount of product was obtained
(entry 11). When CuSO4 was used as catalyst, the yield of the de-
sired product could reach to 70%. Among these reactions men-
tioned above, 1 mL 1,2-dichloroethane was used as both reactant
and solvent. This reaction used a large amount of haloalkanes,
which could be solved by means of an auxiliary solvent. A screening
of the co-solvent such as benzene, 1,4-dioxane, THF, DMF, and
DMSO, DMSO was the most effective in a 91% yield (entries 12e16).
When 1,2-dichloroethane was decreased to 7.5 equiv and 5.0 equiv,
the yields of the desired product were decreased to 74% and 65%,
respectively. Use of a lower catalyst led to a modestly lower yield
(entry 17). Finally, a decrease in the reaction time or the reaction
temperature led to a decrease in yield (entries 18 and 19).
With the optimized conditions in hand (Table 1, entry 16), we
next examined the substrate scope of this transformation. It was
found that a series of the electron-donating groups (e.g., methyl,
methoxy) and electron-withdrawing groups (e.g., chloro) on the
phenyl rings of benzoic peroxyanhydride could be transformed
into the corresponding chloroalkane benzoates in moderate to
excellent yields (Table 2). Even sterically hindered substrates such
as 2-methylbenzoic peroxyanhydride also proved to be excellent
substrates (2n, 2o, 2p). Besides, excellent yields were obtained by
the reaction of benzoic peroxyanhydride derivatives with long-
chain halogenated alkanes, for instance, 1,4-dichlorobutane (2c,
2k, 2o, 2r), 1,5-dichloropentane (2d, 2h, 2l, 2p, 2i), and 1,6-
dichlorohexane (2e, 2i). The reactions between benzoic perox-
yanhydride derivatives and singly halogenated alkanes, for ex-
ample, 1-chlorobutane, 1-bromobutane, and 1-iodoethane could
also proceed smoothly to produce butyl benzoate in 95% yield,
O
X
n
X
O
Cu(OAc)2 (10 mol%)
1,10-phen (10 mol%)
O
X
n
O
+
or
or
t
O
O
O
NaO Bu (3 equiv)
O
DMSO (1 mL)
X
O
n
n
80 oC, 24 h, air
X = Cl, I, Br
O
O
O
Cl
Cl
Cl
3
O
2
O
2a
2b
2c
, X=Cl, 91%
, X=Cl, 85%
, X=Cl, 85%
O
O
O
Cl
Cl
4
Cl
5
O
O
O
Me
Me
2d, X=Cl, 83%
2e, X=Cl, 76%
2f, X=Cl, 85%
O
O
O
O
Cl
3
Cl
4
Cl
5
O
O
Me
Me
Cl
2g, X=Cl, 65%
2h, X=Cl, 64%
2i, X=Cl, 72%
O
O
O
Cl
3
Cl
Cl
O
O
O
4
Cl
Cl
2j, X=Cl, 70%
2k, X=Cl, 90%
2l, X=Cl, 89%
O
O
O
Cl
Cl
Cl
3
O
O
O
MeO
Me
Me
2m
2n
2o
, X=Cl, 71%
, X=Cl, 75%
, X=Cl, 66%
O
O
O
O
O
Cl
Cl
Cl
Cl
Cl
O
4
3
Me
2p, X=Cl, 93%
2q, X=Cl, 95%
2r, X=Cl, 73%
O
O
O
O
Cl
Cl
4
O
O
2s, X=Cl, 95%
2t, X=I, 93%
2u, X=Cl, 95%
O
O
2v, X=Br, 93%
Table 1
Optimization of the cross-coupling of alkyl halides with organic peroxides)a
Reaction conditions: BPO (0.25 mmol), haloalkanes (2.5 mmol), Cu(OAc)2
(10 mol%), 1, 10-phen (10 mol%) at 80 oC under air atmosphere for 24 h,
isolated yield.
Entry Catalyst
(mol %)
Ligand (mol %) Base (equiv) Co-solvent Time Yield
butyl benzoate in 93% yield, and ethyl benzoate in 93% yield (2t,
2u, 2v).
(1 mL)
(h)
(%)b
1
2
Cu(OAc)2 (10) 1,10-phen (10) NaOtBu (3.0)
d
d
d
d
d
d
d
d
d
d
d
d
24
24
24
24
24
24
24
24
24
24
24
24
82
6
4
74
Trace
10
43
17
25
In addition to primary alkyl halides, the reactions of benzoic
peroxyanhydride derivatives with secondary alkyl halides could
also be carried out smoothly. The cases in point are 4-
methylbenzoic peroxyanhydride and 3-chlorobenzoic perox-
yanhydride, which reacted with 2-chlorobutane to generate
the desired products in 65% and 94% yields (3b, 3e), respectively.
However, both secondary cycloalkyl halides and tertiary alkyl
halides were not applicable to the reaction conditions (3f, 3g)
(Table 3).
Having found a suitable system to the corresponding haloalkane
benzoates, we became interested in the reactivity of another hal-
ogen atoms on the haloalkanes. It was found that the bromoester
was obtained in 43% yield and ethane-1,2-diyl dibenzoate was si-
multaneously obtained in 32% yield with the use of 10 equiv 1,2-
dibromoethane (Eq. 1). Interestingly, with 1 equiv 1,2-dibromo-
ethane used, two bromine atoms of 1,2-dibromoethane were
substituted generating ethane-1,2-diyl dibenzoate in 74% yield,
whereas the corresponding bromoester was not detectable (Eq. 2).
Nevertheless, with the use of 1,2-dichloroethane as the reactant,
the yield of ethane-1,2-diyl dibenzoate decreased to 57% (Eq. 3).
1,10-phen (10) NaOtBu (3.0)
NaOtBu (3.0)
3
4
5
6
Cu(OAc)2 (10)
d
Cu(OAc)2 (10) 1,10-phen (10) KOtBu (3.0)
Cu(OAc)2 (10) 1,10-phen (10) LiOtBu (3.0)
Cu(OAc)2 (10) 1,10-phen (10) Na2CO3 (3.0)
Cu(OAc)2 (10) 1,10-phen (10) K3PO4 (3.0)
7
8
CuI (10)
1,10-phen (10) NaOtBu (3.0)
1,10-phen (10) NaOtBu (3.0)
1,10-phen (10) NaOtBu (3.0)
1,10-phen (10) NaOtBu (3.0)
9
CuSCN (10)
CuSO4 (10)
FeCl3 (10)
10
11
12
13
14
15
16
17
18
19c
70
Trace
Trace
Trace
32
85
91
89
84
56
Cu(OAc)2 (10) 1,10-phen (10) NaOtBu (3.0) Benzene
Cu(OAc)2 (10) 1,10-phen (10) NaOtBu (3.0) 1,4-dioxane 24
Cu(OAc)2 (10) 1,10-phen (10) NaOtBu (3.0) THF
Cu(OAc)2 (10) 1,10-phen (10) NaOtBu (3.0) DMF
Cu(OAc)2 (10) 1,10-phen (10) NaOtBu (3.0) DMSO
Cu(OAc)2 (5) 1,10-phen (5) NaOtBu (3.0) DMSO
Cu(OAc)2 (10) 1,10-phen (10) NaOtBu (3.0) DMSO
Cu(OAc)2 (10) 1,10-phen (10) NaOtBu (3.0) DMSO
24
24
24
24
12
24
a
Unless otherwise noted, the reactions were carried out with BPO (0.25 mmol),
haloalkanes (1.0 mL) (entries 1e11), haloalkanes (2.5 mmol) (entries 12e19), cat-
alyst (10 mol %), 1,10-phen (10 mol %), under air atmosphere.
b
Determined by GC.
At 70 ꢀC.
c

214
H.-H. Chen et al. / Tetrahedron 70 (2014) 212e217
Table 3
TEMPO, 1,1-diphenylethylene, or 1,4-cyclohexadiene, had a negli-
gible effect on the yield of this reaction (Eq. 6). These experiments
indicated a radical pathway is less likely in this transformation.
Further mechanistic investigations will be carried out in details in
the future.
Copper-catalyzed cross-coupling of organic peroxides and second alkyl halides
Cu(OAc)2 (10 mol%)
1,10-phen (10 mol%)
O
O
O
+
O
O
t
Cl
O
NaO Bu (3 equiv)
O
DMSO (1 mL)
80 oC, 24 h, air
O
O
O
O
O
O
O
O
O
O
Cu(OAc)2 (10 mol%)
1,10-phen (10 mol%)
O
Me
Cl
Me
3d
O
Cl
3a
, 94%
3b
3c
, 76%
, 65%
, 94%
(6)
O
0.25 mmol
t
NaO Bu (3 equiv)
O
O
+
O
Cl
DMSO (1 mL)
Cl
Cl
O
O
80 oC, 24 h, air
O
(10 equiv)
+
3g
3e, 80%
3f, trace
, trace
Radical Inhibitor
(1 equiv)
Yield
89%
87%
1,4-cyclohexadiene
Reaction conditions: BPO (0.25 mmol), haloalkanes (2.5 mmol), Cu(OAc)2
(10 mol%), 1, 10-phen (10 mol%) at 80 C under air atmosphere for 24 h,
o
TEMPO
isolated yield.
89%
1, 1-diphenylethylene
Based on the results, we can selectively synthesize haloalkane
benzoates or 1,2-diyl dibenzoate with the standard reaction
conditions.
3. Conclusion
In summary, we reported a novel copper-catalyzed reaction of
benzoic peroxyanhydride derivatives with haloalkanes producing
haloalkane benzoate under mild conditions. In this reaction system,
10% Cu(OAc)2/10% 1,10-phenanthroline/3 equiv NaOtBu in DMSO at
80 ꢀC could furnish excellent yields of the desired cross-coupling
product. A number of long-chain halogenated alkanes could un-
dergo the transformation. Besides, both primary and secondary
alkyl halides were also converted to the corresponding products in
high yields with up to 95% under the mild conditions. We anticipate
the system will make this protocol for a potential alternative on
scale-production.
O
O
O
Cu(OAc) (10mol%)
1,10-phen (10 mol%)
NaO Bu (3 equiv)
DMSO (1 mL)
Br
O
Br
O
(1)
Br
O
O
+
O
+
O
O
0.25 mmol
2.5 mmol
43%
32%
80 C, 24 h, air
O
Cu(OAc) (10 mol%)
1,10-phen (10 mol%)
O
O
(2)
O
Br
Br
O
O
O
Br
O
+
+
NaO Bu (3 equiv)
DMSO (1 mL)
80 C, 24 h, air
O
O
0.25 mmol
0.25 mmol
not detected
74%
O
Cu(OAc) (10mol%)
1,10-phen (10 mol%)
O
O
O
Cl
O
O
O
Cl
(3)
Cl
+
O
+
NaO Bu (3 equiv)
DMSO (1 mL)
80 C, 24 h, air
O
O
0.25 mmol
0.25 mmol
not detected
57%
4. Experimental section
To examine the relative reactivities of alkyl halides (RX; X¼Cl,
Br), the following experiments were performed. First, reaction of
benzoic peroxyanhydride with 1-chloro-2-bromoethane in DMSO
under air at 80 ꢀC was monitored by GCꢁMS. The yields of 2-
bromoethyl and 2-chloroethyl benzoate were 42% and 1% by
breaking CeBr bond and CeCl bond, respectively (Eq. 4). In addi-
tion, we also performed a competitive experiment. A mixture of
1,2-dichloroethane and 1,2-dibromoethane was treated with ben-
zoic peroxyanhydride, and it was found that 2-bromoethyl benzo-
ate was obtained in higher yield (Eq. 5). On the basis of these
preliminary results, it may imply that bromine species might be the
more reactive species in these reactions.
4.1. Preparation of benzoyl peroxide analogs15
Benzoyl peroxide analogs were prepared according to literature
procedure. Sodium hydroxide (1.75 g) and 15 mL water were added
into a round-bottom flask, 2.0 mL hydrogen peroxide and 0.025 g
sodium dodecyl sulfate were added dropwise at 0 ꢀC, 0.013 mol
benzoyl chloride analogs were added dropwise slowly under stir-
ring. The reaction mixture was allowed to stir an additional 2.5 h.
White solid could be obtained in this reaction. The solid was filtered
out and washed with methanol/water (1:1). Then, it was placed in
vacuum oven to dry 24 h.
O
Cl
O
4.2. General procedures for the Csp3eO cross-coupling of
benzoyl peroxide analogs with haloalkanes
Cu(OAc)2 (10mol%)
O
1,10-phen (10 mol%)
42%
Br
O
(4)
+
Cl
t
O
NaO Bu (3 equiv)
O
O
DMSO (1 mL)
Br
Cl
Br
In air, Cu catalyst (0.025 mmol), benzoyl peroxide analogs
(0.25 mmol), ligand (0.025 mmol), base (3.0 equiv) were added to
a Schlenk tube equipped with a magneton. Halogenated alkanes
(2.5 mmol) and DMSO (1.0 mL) were added in turn. The reaction
mixture was stirred at the mentioned temperature for the indicated
amount of time. The resulting solution mixture was diluted by ethyl
acetate (10.0 mL). Benzophenone (91.1 mg, 0.5 mmol) was added as
internal standard. The yield of the product was determined by GC.
80 oC, 24 h, air
O
0.25 mmol
2.5 mmol
1%
O
Cl
O
Cl
O
Cu(OAc)2 (10mol%)
1,10-phen (10 mol%)
2.5 mmol
O
O
10%
+
(5)
t
NaO Bu (3 equiv)
O
O
Br
DMSO (1 mL)
0.5 mmol
Br
80 oC, 24 h, air
O
2.5 mmol
31%
4.2.1. 2-Chloroethyl benzoate (2a).6 According to the general pro-
cedure, benzoic peroxyanhydride (0.25 mmol, 61 mg) was allowed
to react with 1,2-dichloroethane (2.5 mmol) under 80 ꢀC for 24 h.
The product was isolated as a yellow oil (82.4 mg, 91% yield). 1H
NMR (600 MHz, CDCl3) 8.03 (d, J¼7.1 Hz, 2H), 7.58 (t, J¼7.4 Hz, 1H),
Finally, to further comprehend whether the reaction proceeded
via a radical pathway, we conducted a series of control experi-
ments. The addition of radical inhibitors, including 1.0 equiv of

H.-H. Chen et al. / Tetrahedron 70 (2014) 212e217
215
7.45 (t, J¼7.5 Hz, 2H), 4.57 (t, J¼5.7 Hz, 2H), 3.81 (t, J¼5.7 Hz,
2H); 13C NMR (151 MHz, CDCl3)
d
166.7, 143.5, 129.5, 129.1, 127.6,
2H); 13C NMR (75 MHz, CDCl3)
64.5, 41.7.
d
166.2, 133.3, 129.8, 129.7, 128.4,
64.5, 44.8, 32.2, 28.0, 23.5, 21.7; HRMS calcd for C13H17ClO2 (Mþ)
240.0918; found: 240.0922.
4.2.2. 3-Chloropropyl benzoate (2b).7 According to the general
procedure, benzoic peroxyanhydride (0.25 mmol, 61 mg) was
allowed to react with 1,3-dichloropropane (2.5 mmol) under 80 ꢀC
for 24 h. The product was isolated as a yellow oil (83.7 mg, 85%
4.2.9. 6-Chlorohexyl 4-methylbenzoate (2i). According to the gen-
eral procedure, 4-methylbenzoic peroxyanhydride (0.25 mmol,
67.5 mg) was allowed to react with 1,6-dichlorohexane (2.5 mmol)
under 80 ꢀC for 24 h. The product was isolated as a yellow oil
yield). 1H NMR (600 MHz, CDCl3)
d
8.03 (d, J¼7.1 Hz, 2H), 7.56 (t,
(91.5 mg, 72% yield). 1H NMR (600 MHz, CDCl3)
d
7.92 (d, J¼8.2 Hz,
J¼7.4 Hz, 1H), 7.44 (t, J¼7.8 Hz, 2H), 4.47 (t, J¼6.0 Hz, 2H), 3.70 (t,
2H), 7.22 (d, J¼8.0 Hz, 2H), 4.29 (t, J¼6.6 Hz, 2H), 3.52 (t, J¼6.7 Hz,
J¼6.4 Hz, 2H), 2.23 (m, 2H); 13C NMR (151 MHz, CDCl3)
d 166.4,
2H), 2.38 (s, 3H), 1.84e1.71 (m, 4H), 1.54e1.37 (m, 4H); 13C NMR
133.1, 123.0, 129.6, 128.4, 61.6, 41.3, 31.7.
(151 MHz, CDCl3) d 166.7, 143.5, 129.5, 129.0, 127.6, 64.6, 44.9, 32.5,
28.6, 26.6, 25.4, 21.6; HRMS calcd for C14H19 ClO2 (Mþ) 254.1074;
found: 254.1079.
4.2.3. 4-Chlorobutyl benzoate (2c).8 According to the general pro-
cedure, benzoic peroxyanhydride (0.25 mmol, 61 mg) was allowed
to react with 1,4-dichlorobutane (2.5 mmol) under 80 ꢀC for 24 h.
The product was isolated as a yellow oil (90.1 mg, 85% yield). 1H
4.2.10. 2-Chloroethyl 4-chlorobenzoate (2j).10 According to the
general procedure, 4-chlorobenzoic peroxyanhydride (0.25 mmol,
77.5 mg) was allowed to react with 1,2-dichloroethane (2.5 mmol)
under 80 ꢀC for 24 h. The product was isolated as a yellow oil
NMR (600 MHz, CDCl3)
d
8.02 (d, J¼8.4 Hz, 2H), 7.54 (t, J¼7.5 Hz,
1H), 7.42 (t, J¼7.8 Hz, 2H), 4.34 (t, J¼5.8 Hz, 2H), 3.59 (t, J¼5.9 Hz,
2H), 1.93 (m, 4H); 13C NMR (151 MHz, CDCl3)
129.5, 128.3, 64.1, 44.5, 29.3, 26.2.
d
166.5, 132.9, 130.2,
(76.3 mg, 70% yield). 1H NMR (600 MHz, CDCl3)
d
7.99 (d, J¼8.6 Hz,
2H), 7.42 (d, J¼8.5 Hz, 2H), 4.60 (t, J¼6.0 Hz, 2H), 3.80 (t, J¼5.4 Hz,
2H); 13C NMR (151 MHz, CDCl3)
64.6, 41.6.
d 165.3, 139.8, 131.1, 128.8, 128.0,
4.2.4. 5-Chloroheptyl benzoate (2d).8 According to the general
procedure, benzoic peroxyanhydride (0.25 mmol, 61 mg) was
allowed to react with 1,5-dichloropentane (2.5 mmol) under 80 ꢀ
C
4.2.11. 2-Chloroethyl 4-chlorobenzoate (2k).8 According to the
general procedure, 4-chlorobenzoic peroxyanhydride (0.25 mmol,
77.5 mg) was allowed to react with 1,4-dichlorobutane (2.5 mmol)
under 80 ꢀC for 24 h. The product was isolated as a yellow oil
for 24 h. The product was isolated as a yellow oil (93.8 mg, 83%
yield). 1H NMR (600 MHz, CDCl3)
d
8.03 (d, J¼7.0 Hz, 2H), 7.54 (t,
J¼7.4 Hz, 1H), 7.42 (t, J¼7.7 Hz, 2H), 4.31 (t, J¼6.5 Hz, 2H), 3.55 (t,
J¼6.6 Hz, 2H), 1.86e1.81 (m, 2H), 1.80e1.76 (m, 2H), 1.62e1.56 (m,
(110.7 mg, 90% yield). 1H NMR (600 MHz, CDCl3)
d
7.96 (d, J¼8.6 Hz,
2H); 13C NMR (151 MHz, CDCl3)
44.8, 32.2, 28.0, 23.4.
d
132.9, 130.3, 129.5, 128.3, 64.6,
2H), 7.41 (d, J¼8.6 Hz, 2H), 4.35 (t, J¼6.0 Hz, 2H), 3.60 (t, J¼6.1 Hz,
2H), 1.97e1.91 (m, 4H); 13C NMR (151 MHz, CDCl3)
d 165.7, 139.4,
130.9, 128.7, 128.6, 64.4, 44.5, 29.2, 26.1.
4.2.5. 6-Chlorohexyl benzoate (2e).9 According to the general pro-
cedure, benzoic peroxyanhydride (0.25 mmol, 61 mg) was allowed
to react with 1,6-dichlorohexane (2.5 mmol) under 80 ꢀC for 24 h.
The product was isolated as a yellow oil (101.1 mg, 76% yield). 1H
4.2.12. 5-Chloroheptyl 4-chlorobenzoate (2l). According to the
general procedure, 4-chlorobenzoic peroxyanhydride (0.25 mmol,
77.5 mg) was allowed to react with 1,5-dichloropentane (2.5 mmol)
under 80 ꢀC for 24 h. The product was isolated as a yellow oil
NMR (600 MHz, CDCl3)
d
8.03 (d, J¼7.1 Hz, 2H), 7.54 (t, J¼7.4 Hz,1H),
7.42 (t, J¼7.7 Hz, 2H), 4.31 (t, J¼6.6 Hz, 2H), 3.53 (t, J¼6.6 Hz, 2H),
(117.0 mg, 89% yield). 1H NMR (600 MHz, CDCl3)
d
7.96 (d, J¼6.7 Hz,
1.75e1.79 (m, 4H), 1.52e1.44 (m, 4H); 13C NMR (151 MHz, CDCl3)
2H), 7.40 (d, J¼6.6 Hz, 2H), 4.31 (t, J¼6.5 Hz, 2H), 3.56 (t, J¼5.6 Hz,
d
166.6, 132.8, 130.4, 129.5, 128.3, 64.8, 44.9, 32.5, 28.6, 26.6, 25.4.
2H), 1.86e1.81 (m, 2H), 1.81e1.77 (m, 2H), 1.62e1.56 (m, 2H). 13C
NMR (151 MHz, CDCl3)
d 165.9, 163.6, 131.8, 121.9, 113.7, 64.2, 55.5,
4.2.6. 2-Chloroethyl 4-methylbenzoate (2f).6 According to the gen-
eral procedure, 4-methylbenzoic peroxyanhydride (0.25 mmol,
67.5 mg) was allowed to react with 1,2-dichloroethane (2.5 mmol)
under 80 ꢀC for 24 h. The product was isolated as a yellow oil
41.8, 29.7, 28.2. HRMS calcd for C12H14Cl2O2 (Mþ) 260.0371; found:
260.0375.
4.2.13. 2-Chloroethyl 4-methoxylbenzoate (2m).11 According to the
general procedure, 4-methoxylbenzoic peroxyanhydride (0.25
mmol, 75.5 mg) was allowed to react with 1,5-dichloroheptane
(2.5 mmol) under 80 ꢀC for 24 h. The product was isolated as
(82.5 mg, 85% yield). 1H NMR (600 MHz, CDCl3)
d
7.95 (d, J¼8.2 Hz,
2H), 7.24 (d, J¼8.9 Hz, 2H), 4.55 (t, J¼5.4 Hz, 2H), 3.80 (t, J¼6.0 Hz,
2H), 2.41 (s, 3H); 13C NMR (151 MHz, CDCl3)
129.1, 126.8, 64.3, 41.7, 21.7.
d 166.2, 144.0, 129.8,
a yellow oil (76.2 mg, 71% yield). 1H NMR (600 MHz, CDCl3)
d 8.01
(d, J¼8.7 Hz, 2H), 6.92 (d, J¼8.7 Hz, 2H), 4.53 (t, J¼5.4 Hz, 2H), 3.85
4.2.7. 4-Chlorobutyl 4-methylbenzoate (2g).8 According to the
general procedure, 4-methylbenzoic peroxyanhydride (0.25 mmol,
67.5 mg) was allowed to react with 1,4-dichlorobutane (2.5 mmol)
under 80 ꢀC for 24 h. The product was isolated as a yellow oil
(s, 3H), 3.79 (t, J¼5.4 Hz, 2H); 13C NMR (151 MHz, CDCl3)
d 166.9,
163.3, 131.6, 122.5, 113.6, 55.4, 51.9.
4.2.14. 2-Chloroethyl 2-methylbenzoate (2n). According to the
general procedure, 2-methylbenzoic peroxyanhydride (0.25 mmol,
67.5 mg) was allowed to react with 1,2-dichloroethane (2.5 mmol)
under 80 ꢀC for 24 h. The product was isolated as a yellow oil
(73.5 mg, 65% yield). 1H NMR (600 MHz, CDCl3)
d
7.91 (d, J¼8.2 Hz,
2H), 7.22 (d, J¼8.1 Hz, 2H), 4.33 (t, J¼5.8 Hz, 2H), 3.60 (t, J¼6.1 Hz,
2H), 2.39 (s, 3H), 1.93e1.92 (m, 4H); 13C NMR (151 MHz, CDCl3)
d
166.6, 143.6, 129.6, 129.1, 127.4, 63.9, 44.5, 29.3, 26.2, 21.7.
(77.3 mg, 75% yield). 1H NMR (600 MHz, CDCl3)
d
7.96 (d, J¼7.3 Hz,
1H), 7.41 (t, J¼7.9 Hz, 1H), 7.27e7.24 (m, 2H), 4.55 (t, J¼6.0 Hz, 2H),
4.2.8. 5-Chloroheptyl 4-methylbenzoate (2h). According to the
general procedure, 4-methylbenzoic peroxyanhydride (0.25 mmol,
67.5 mg) was allowed to react with 1,5-dichloropentane (2.5 mmol)
under 80 ꢀC for 24 h. The product was isolated as a yellow oil
3.81 (t, J¼5.4 Hz, 2H), 2.61 (s, 3H); 13C NMR (151 MHz, CDCl3)
d
167.1, 140.5, 132.3, 131.7, 130.8, 128.8, 125.8, 64.3, 41.8, 21.9; HRMS
calcd for C10H11ClO2 (Mþ) 198.0448; found: 198.0450.
(76.8 mg, 64% yield). 1H NMR (600 MHz, CDCl3)
2H), 7.23 (d, J¼8.0 Hz, 2H), 4.30 (t, J¼6.5 Hz, 2H), 3.55 (t, J¼6.6 Hz,
2H), 2.40 (s, 3H),1.93e1.81 (m, 2H),1.81e1.73 (m, 2H),1.65e1.53 (m,
d
7.92 (d, J¼8.1 Hz,
4.2.15. 4-Chlorobutyl 2-methylbenzoate (2o). According to the
general procedure, 2-methylbenzoic peroxyanhydride (0.25 mmol,
67.5 mg) was allowed to react with 1,2-dichloroethane (2.5 mmol)

216
H.-H. Chen et al. / Tetrahedron 70 (2014) 212e217
under 80 ꢀC for 24 h. The product was isolated as a yellow oil
(74.6 mg, 66% yield). 1H NMR (600 MHz, CDCl3)
(m, 2H), 0.97 (t, J¼7.4 Hz, 3H); 13C NMR (151 MHz, CDCl3)
d 166.6,
d
7.90 (d, J¼8.3 Hz,
132.8, 130.5, 129.5, 128.3, 64.8, 30.8, 19.3, 13.8.
1H), 7.39 (t, J¼7.5 Hz, 1H), 7.25e7.23 (m, 2H), 4.33 (t, J¼6.0 Hz, 2H),
3.60 (t, J¼6.1 Hz, 2H), 2.59 (s, 3H), 1.94e1.92 (m, 4H); 13C NMR
4.2.22. Butyl benzoate (2v).12 According to the general procedure,
benzoic peroxyanhydride (0.25 mmol, 61 mg) was allowed to react
with 1-bromobutane (2.5 mmol) under 80 ꢀC for 24 h. The product
was isolated as a yellow oil (82.3 mg, 93% yield). 1H NMR (600 MHz,
(151 MHz, CDCl3)
d 167.5, 140.2, 132.0, 131.7, 130.51, 129.5, 125.7,
63.9, 44.6, 29.3, 26.2, 21.8; HRMS calcd for C12H15ClO2 (Mþ)
226.0761; found: 226.0767.
CDCl3)
d
8.04 (d, J¼7.8 Hz, 2H), 7.54 (t, J¼7.4 Hz, 1H), 7.43 (t,
4.2.16. 4-Chlorobutyl 3-chlorobenzoate (2p). According to the gen-
eral procedure, 2-methylbenzoic peroxyanhydride (0.25 mmol,
67.5 mg) was allowed to react with 1,5-dichloropentane (2.5 mmol)
under 80 ꢀC for 24 h. The product was isolated as a blue oil
J¼7.7 Hz, 2H), 4.32 (t, J¼6.6 Hz, 2H), 1.78e1.71 (m, 2H), 1.52e1.44
(m, 2H), 0.97 (t, J¼7.4 Hz, 3H); 13C NMR (151 MHz, CDCl3)
d 166.6,
132.8, 130.5, 129.5, 128.3, 64.8, 30.8, 19.3, 13.8.
(111.6 mg, 93% yield). 1H NMR (600 MHz, CDCl3)
d
7.90 (d, J¼9.3 Hz,
4.2.23. sec-Butyl benzoate (3a).17 According to the general pro-
cedure, benzoyl peroxide (0.25 mmol, 61 mg) was allowed to react
with 2-chlorobutane (2.5 mmol) under 80 ꢀC for 24 h. The product
was isolated as a yellow oil (83.7 mg, 94% yield). 1H NMR (600 MHz,
1H), 7.39 (t, J¼6.9 Hz, 1H), 7.24 (t, J¼7.2 Hz, 2H), 4.30 (t, J¼6.5 Hz,
2H), 3.56 (t, J¼6.6 Hz, 2H), 2.59 (s, 3H), 1.91e1.82 (m, 2H), 1.82e1.76
(m, 2H), 1.63e1.58 (m, 2H); 13C NMR (151 MHz, CDCl3)
d 167.7, 140.1,
131.9, 131.7, 130.5, 129.7, 125.7, 64.4, 44.8, 32.2, 28.0, 23.5, 21.1;
CDCl3)
d
8.04 (d, J¼7.0 Hz, 2H), 7.54 (t, J¼7.4 Hz, 1H), 7.43 (t,
HRMS calcd for C13H17ClO2 (Mþ) 240.0917; found: 240.0910.
J¼7.8 Hz, 2H), 5.12e5.06 (m, 1H), 1.33 (d, J¼6.3 Hz, 3H), 0.96 (t,
J¼7.5 Hz, 3H); 13C NMR (151 MHz, CDCl3)
d 166.2,132.7, 130.9, 129.5,
4.2.17. 2-Chloroethyl 3-chlorobenzoate (2q).10 According to the
general procedure, 3-chlorobenzoic peroxyanhydride (0.25
mmol, 77.5 mg) was allowed to react with 1,2-dichloro
ethane (2.5 mmol) under 80 ꢀC for 24 h. The product was iso-
lated as a yellow oil (103.8 mg, 95% yield). 1H NMR (600 MHz,
128.3, 72.8, 28.9, 19.6, 9.8.
4.2.24. sec-Butyl 4-methylbenzoate (3b).15 According to the general
procedure, 4-methylbenzoic peroxyanhydride (0.25 mmol,
67.5 mg) was allowed to react with 2-chlorobutane (2.5 mmol)
under 80 ꢀC for 24 h. The product was isolated as a yellow oil
CDCl3)
d
8.02 (s, 1H), 7.94 (d, J¼8.7 Hz, 1H), 7.53 (d, J¼8.0 Hz, 1H),
7.38 (t, J¼7.9 Hz, 1H), 4.56 (t, J¼6.4 Hz, 1H), 3.80 (t, J¼5.3 Hz, 1H);
(62.1 mg, 65% yield). 1H NMR (600 MHz, CDCl3)
d
7.93 (d, J¼8.2 Hz,
13C NMR (151 MHz, CDCl3)
127.9, 64.8, 41.6.
d
165.0, 134.6, 133.3, 131.3, 129.9, 129.8,
2H), 7.22 (d, J¼8.0 Hz, 2H), 5.10e5.04 (m, 1H), 2.39 (s, 3H), 1.31 (d,
J¼6.3 Hz, 3H), 0.96 (t, J¼7.5 Hz, 3H); 13C NMR (151 MHz, CDCl3)
d
166.3, 143.3, 129.5, 129.0, 128.1, 72.6, 29.0, 21.6, 19.6, 9.8.
4.2.18. 4-Chlorobutyl 3-chlorobenzoate (2r). According to the gen-
eral procedure, 3-chlorobenzoic peroxyanhydride (0.25 mmol,
77.5 mg) was allowed to react with 1,4-dichlorobutane (2.5 mmol)
under 80 ꢀC for 24 h. The product was isolated as a yellow oil
4.2.25. sec-Butyl 4-chlorobenzoate (3c).14 According to the general
procedure, 4-chlorobenzoic peroxyanhydride (0.25 mmol, 77.5 mg)
was allowed to react with 2-chlorobutane (2.5 mmol) under 80 ꢀC
for 24 h. The product was isolated as a yellow oil (80.6 mg, 76%
(89.8 mg, 73% yield). 1H NMR (600 MHz, CDCl3)
d 7.97 (s, 1H), 7.89
(d, J¼6.9 Hz, 1H), 7.50 (d, J¼9.0 Hz, 1H), 7.35 (t, J¼7.9 Hz, 1H), 4.33 (t,
yield). 1H NMR (600 MHz, CDCl3)
d
7.96 (d, J¼8.3 Hz, 2H), 7.39 (d,
J¼5.9 Hz, 2H), 3.59 (t, J¼6.0 Hz, 2H), 1.91 (m, 4H); 13C NMR
J¼8.5 Hz, 2H), 5.10e5.04 (m, 1H), 1.32 (d, J¼6.2 Hz, 3H), 0.95 (t,
(151 MHz, CDCl3)
d
165.3,134.5,133.0,131.9, 129.7, 129.6,127.7, 64.5,
J¼7.5 Hz, 3H); 13C NMR (151 MHz, CDCl3)
d 165.4,139.0,130.8,129.3,
44.5, 29.2, 26.1; HRMS calcd for C11H12Cl2O2 (Mþ) 246.0214; found:
246.0209.
128.6, 73.2, 28.9, 19.5, 9.7.
4.2.26. sec-Butyl 2-methylbenzoate (3d).16 According to the general
procedure, 3-chlorobenzoic peroxyanhydride (0.25 mmol, 67.5 mg)
was allowed to react with 2-chlorobutane (2.5 mmol) under 80 ꢀC
for 24 h. The product was isolated as a yellow oil (90.3 mg, 94%
4.2.19. 4-Chlorobutyl 3-chlorobenzoate (2s). According to the gen-
eral procedure, 3-chlorobenzoic peroxyanhydride (0.25 mmol,
77.5 mg) was allowed to react with 1,5-dichloropentane
(2.5 mmol) under 80 ꢀC for 24 h. The product was isolated as
yield). 1H NMR (600 MHz, CDCl3)
d
7.90 (d, J¼7.6 Hz, 1H), 7.37 (t,
a yellow oil (123.5 mg, 95% yield). 1H NMR (600 MHz, CDCl3)
d
8.00
J¼7.5 Hz, 1H), 7.23 (t, J¼7.6 Hz, 2H), 5.12e5.06 (m, 1H), 2.60 (s, 3H),
(s, 1H), 7.91 (d, J¼7.8 Hz, 1H), 7.52 (d, J¼8.0 Hz, 1H), 7.38 (t,
J¼7.9 Hz, 1H), 4.33 (t, J¼6.6 Hz, 2H), 3.56 (t, J¼6.6 Hz, 2H),
1.88e1.82 (m, 2H), 1.82e1.77 (m, 2H), 1.62e1.57 (m, 2H); 13C NMR
1.34 (d, J¼6.3 Hz, 3H), 0.98 (t, J¼7.5 Hz, 3H); 13C NMR (151 MHz,
CDCl3)
d 167.4, 139.8, 131.7, 131.6, 130.4, 130.3, 125.6, 72.6, 29.0, 21.8,
19.6, 9.8.
(151 MHz, CDCl3)
d 165.4, 134.5, 132.9, 132.0, 129.7, 129.6, 127.7,
65.1, 44.8, 32.1, 27.9, 23.4; HRMS calcd for C12H14Cl2O2 (Mþ)
260.0371; found: 260.0377.
4.2.27. sec-Butyl 3-chlorobenzoate (3e).14 According to the general
procedure, 4-chlorobenzoic peroxyanhydride (0.25 mmol, 77.5 mg)
was allowed to react with 2-chlorobutane (2.5 mmol) under 80 ꢀC
for 24 h. The product was isolated as a yellow oil (84.8 mg, 80%
4.2.20. Ethyl benzoate (2t).8 According to the general procedure,
benzoic peroxyanhydride (0.25 mmol, 61 mg) was allowed to react
with chloroethane (2.5 mmol) under 80 ꢀC for 24 h. The product
was isolated as a yellow oil (69.8 mg, 93% yield). 1H NMR (600 MHz,
yield). 1H NMR (600 MHz, CDCl3)
d
8.00 (s, 1H), 7.92 (d, J¼7.8 Hz,
1H), 7.50 (d, J¼8.0 Hz, 1H), 7.36 (t, J¼7.9 Hz, 1H), 5.11e5.05 (m, 1H),
1.75e1.64 (m, 2H), 1.32 (d, J¼6.3 Hz, 3H), 0.96 (t, J¼7.5 Hz, 3H); 13
C
CDCl3)
d
8.04 (d, J¼7.1 Hz, 2H), 7.54 (t, J¼7.4 Hz, 1H), 7.42 (t,
NMR (151 MHz, CDCl3)
73.5, 28.9, 19.5, 9.8.
d 16.0, 134.4, 132.7, 132.6, 129.6, 129.5, 127.6,
J¼7.8 Hz, 2H), 4.37 (q, J¼7.2 Hz, 2H), 1.39 (t, J¼7.1 Hz, 3H); 13C NMR
(151 MHz, CDCl3)
d 166.6, 132.8, 130.5, 129.5, 128.3, 60.9, 14.3.
4.3. Further synthetic transformations of benzoyl peroxide
4.2.21. Butyl benzoate (2u).12 According to the general procedure,
benzoic peroxyanhydride (0.25 mmol, 61 mg) was allowed to react
with 1-chlorobutane (2.5 mmol) under 80 ꢀC for 24 h. The product
was isolated as a yellow oil (84.6 mg, 95% yield). 1H NMR (600 MHz,
In air, Cu catalyst (0.025 mmol), benzoyl peroxide (0.25 mmol,
61 mg), ligand (0.025 mmol), base (3.0 equiv) were added to
a Schlenk tube equipped with a magneton. 1,2-Dichloroethane
CDCl3)
d
8.04 (d, J¼7.8 Hz, 2H), 7.54 (t, J¼7.4 Hz, 1H), 7.43 (t,
(0.25 mmol, 20.0
reaction mixture was stirred at the mentioned temperature for the
mL) and DMSO (1.0 mL) were added in turn. The
J¼7.7 Hz, 2H), 4.32 (t, J¼6.6 Hz, 2H), 1.78e1.71 (m, 2H), 1.52e1.44

H.-H. Chen et al. / Tetrahedron 70 (2014) 212e217
217
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indicated amount of time. The resulting solution mixture was
dilutioned by ethyl acetate (10.0 mL). Benzophenone (45.6 mg,
0.25 mmol) was added as an internal standard. The product was
isolated as a white solid (38.8 mg, 57% yield).
According to the general procedure, benzoyl peroxide
(0.25 mmol, 61 mg) was allowed to react with 1,2-dibromoethane
(0.25 mmol, 22.0 m
L) under 80 ꢀC for 24 h. The product was iso-
3. (a) Raymond, T. G.; Claire, L. M.; Nicholas, G. S.; Eun, S. J.; Mae, J. B. A.; Thomas,
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lated as a white solid (50.3 mg, 74% yield).
4.3.1. Ethane-1,2-diyl dibenzoate.6 The product yield was de-
termined by GC 1H NMR (600 MHz, CDCl3)
d
8.05 (d, J¼7.1 Hz, 2H),
ꢀ
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7.56 (t, J¼7.4 Hz, 1H), 7.44 (t, J¼7.8 Hz, 2H), 4.66 (s, 2H); 13C NMR
(151 MHz, CDCl3)
d 166.4, 133.2, 129.8, 129.7, 62.7.
4.3.2. 2-Bromoethyl benzoate.13 According to the general pro-
cedure, benzoic peroxyanhydride (0.25 mmol, 61 mg) was allowed
to react with 1,2-bromoethane (2.5 mmol) under 80 ꢀC for 24 h. The
product was isolated as a yellow oil (48.8 mg, 43% yield). 1H NMR
(600 MHz, CDCl3)
d
8.06 (d, J¼7.2 Hz, 2H), 7.57 (t, J¼7.4 Hz, 1H), 7.45
(t, J¼7.8 Hz, 2H), 4.62 (t, J¼6.1 Hz, 2H), 3.64 (t, J¼6.1 Hz, 2H). 13C
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NMR (151 MHz, CDCl3) d 166.0, 133.2, 129.7, 129.6, 128.4, 64.2, 28.8.
Acknowledgements
We gratefully acknowledge financial support from the National
Natural Science Foundation of China (Nos. 21272050, 21072040,
21071040) and the Program for New Century Excellent Talents in
University of the Chinese Ministry of Education (NCET-11-0627).
Supplementary data
Copies of 1H and 13C NMR spectra for the products. These ma-
terials are available free of charge via the Internet at http://pub-
s.acs.org. Supplementary data associated with this article can be
found in the online version, at http://dx.doi.org/10.1016/
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