Copper-mediated alkylation of furan and thiophene derivatives with cyclic ethers

Article abstract of DOI:10.1016/j.tet.2016.10.014

An efficient and complementary copper-catalyzed alkylation of (benzo)furans/(benzo)thiophenes with cyclic ethers was reported. A broad range of C2 heteroaryl-substituted cyclic ethers were obtained in moderate to good yields. The results of control experi

Full text of DOI:10.1016/j.tet.2016.10.014

Accepted Manuscript
Copper-mediated alkylation of furan and thiophene derivatives with cyclic ethers
Chenyang Wang, Ming Gong, Mengmeng Huang, Yabo Li, Jung Keun Kim, Yangjie
Wu
PII:
S0040-4020(16)31036-5
10.1016/j.tet.2016.10.014
TET 28155
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 21 July 2016
Revised Date: 30 September 2016
Accepted Date: 8 October 2016
Please cite this article as: Wang C, Gong M, Huang M, Li Y, Kim JK, Wu Y, Copper-mediated alkylation
of furan and thiophene derivatives with cyclic ethers, Tetrahedron (2016), doi: 10.1016/j.tet.2016.10.014.
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ACCEPTED MANUSCRIPT
Graphical Abstract
An efficient and complementary copper-catalyzed alkylation of (benzo)furans/(benzo)thiophenes with cyclic ethers was
reported. A broad range of C2 heteroaryl-substituted cyclic ethers were obtained in moderate to good yields. The results of
control experiments indicated that this transformation might proceed via a radical process.
Leave this area blank for abstract info.
Copper-mediated Alkylation of Furan and
Thiophene Derivatives with Cyclic Ethers
Chenyang Wang, Ming Gong, Mengmeng Huang, Yabo Li,* Jung Keun Kim, Yangjie Wu*
College of Chemistry and Molecular Engineering, Henan Key Laboratory of Chemical Biology and Organic
Chemistry, Key Laboratory of Applied Chemistry of Henan Universities, Collaborative Innovation Center of
New Drug Research and Safety Evaluation, Zhengzhou University, Henan Province, Zhengzhou 450052, PR
China. E-mail: wyj@zzu.edu.cn; liyabo007@126.com; Fax: +86-371-67767993

ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Copper-mediated alkylation of furan and thiophene derivatives with cyclic ethers
Chenyang Wang, Ming Gong, Mengmeng Huang, Yabo Li,* Jung Keun Kim, Yangjie Wu*
College of Chemistry and Molecular Engineering, Henan Key Laboratory of Chemical Biology and Organic Chemistry, Key Laboratory of Applied Chemistry of
Henan Universities, Collaborative Innovation Center of New Drug Research and Safety Evaluation, Zhengzhou University, Henan Province, Zhengzhou 450052,
PR China. E-mail: wyj@zzu.edu.cn; liyabo007@126.com; Fax: +86-371-67767993
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
An
efficient
and
complementary
copper-catalyzed
alkylation
of
(benzo)furans/(benzo)thiophenes with cyclic ethers was reported. A broad range of C2
heteroaryl-substituted cyclic ethers were obtained in moderate to good yields. The results of
control experiments indicated that this transformation might proceed via a radical process.
Available online
2009 Elsevier Ltd. All rights reserved
.
Keywords:
Alkylation
Heteroaromatic
CDC reaction
Radical reaction
1. Introduction
product 3aa was observed (Table 1, entry 1). Increasing the
catalyst loading to 20 mol %, the yield achieved to 63% (Table 1,
entry 2). Other copper salts could not improve the product yield,
except CuI (Table 1, entries 3-6). It was found that di-tert-butyl
The five- or six-membered cyclic ethers widely exist in
natural and non-natural products including ligands, nucleosides,
annonaceous actogenins and macrolides.1 Owing to their
chemical stability, the direct construction of cyclic ethers onto
other molecules is still a challenging task. Recently, the cross-
dehydrogenative coupling (CDC) reaction has become a strategy
to generate more complex molecules due to its high atom-
economy, easy operation and environment friendly.2 Using this
methodology, the direct C-H activation of simple ethers with
different reaction candidates (such as alkanes,3 olefins,4 alkynes,5
carboxylic acids,6 alcohols7 and heteroarenes8) has been
successfully achieved. However, the application of heteroarenes
into this transformation was mainly limited to (benzo)azoles,8a-c
(benzo)thiazoles,8d indoles,8e,8f pyridines and quinolones8g.
Although furans and thiophenes are important building blocks
that frequently appear in organic synthesis,9 the alkylation with
simple ethers were rarely explored. Only one example of CDC
reaction was related to the conversion of benzofuran with 1,4-
dioxane.8f Therefore, to develop an efficient and complementary
O
O
Cat., Oxidant
H
H
+
O
O
O
Additive, Time, T
O
1a
3aa
2a
Table 1. Optimization of the reaction conditions.a
Entry
Catalyst
Cu(OAc)2
Cu(OAc)2
CuBr2
CuI
CuCl
CuBr
CuI
Oxidant
DTBP
DTBP
DTBP
DTBP
DTBP
DTBP
Additive
Yield/%b
41
63
55
83
63
42
trace
1
2
3
4
5
6
7
KI
KI
KI
KI
KI
KI
KI
TBHP (5-6 M
in decane)
Dicumyl
peroxide
Benzoyl
peroxide
DTBP
8
9
CuI
CuI
KI
KI
trace
trace
protocol
via
direct
C-H
alkylation
of
(benzo)furans/(benzo)thiophenes with cyclic ethers is highly
desirable. On the basis of our previous work,10 herein we report
an atom economic copper-catalyzed oxidative CDC reaction of
(benzo)furans/(benzo)thiophenes with cyclic ethers.
10
11
12
13
14
15
CuI
CuI
CuI
CuI
CuI
CuI
NaI
TBAI
PPh3
Xphos
--
45
22
40
51
43
51c
DTBP
DTBP
DTBP
DTBP
2. Results and discussion
DTBP
KI
a
Initially, the direct alkylation of benzofuran (1a) with 1,4-
dioxane (2a) was carried out in the presence of Cu(OAc)2 (10
mol %), KI (20 mol %) and DTBP (3 equiv.) at 120 C. A
Reaction conditions: 1a (0.25 mmol), catalyst (10-20 mol %),
additive (20 mol %), oxidant (3 equiv.), 1,4-dioxane (1.5 mL), in a
o
o
c
sealed tube under N2 at 120 C (oil bath) for 24 h. b Isolated yield.
110 oC.
relatively low but promising isolated yield 41% of desired

2
Tetrahedron
ACCEPTED MANUSCRIPT
peroxide (DTBP) was the best oxidant, and KI was more
the direct alkylation of other heterocycles (such as dithiophene,
efficient additive (Table 1, entries 7-14). The alkylation could not
proceed smoothly at lower temperature (Table 1, entry 15). In
addition, the structure of 3aa in crystalline state was established
by X-ray diffraction analysis.
benzothiazole, benzoazole and pyrrole) with 1,4-dioxane were
explored, giving the corresponding coupled products 3ua-3xa in
86%, 66%, 73% and 70%, respectively.
It was found that the standard reaction conditions for 1,4-
dioxane were not suitable for other cyclic ethers (such as 1,3-
dioxolane, tetrahydro-2H-pyran and tetrahydrofuran). Surprisedly,
these cyclic ethers could smoothly react with (benzo)furans in the
presence of Xphos. Under the modified reaction conditions, 1,3-
dioxolane, tetrahydro-2H-pyran and tetrahydrofuran (THF) were
well tolerated to afford the corresponding targets in moderate to
good yields (Scheme 2). 1,3-Dioxolane (3b) could be smoothly
transformed into C2- and C4-substituted mixture with 80%
combined yield (3ab1 and 3ab2).
Scheme 1. Regiosepecific C2 coupling of heterocycles with
1,4-dioxane.a
R1
R1
CuI (20 mol %),
KI (20 mol %)
O
O
H
+
H
DTBP (3 equiv.),
120 C, 24 h
X
X
O
R2
O
R2
2a
1
3
X = O, S
O
Br
O
O
O
O
O
O
O
O
O
O
O
O
3aa, 83%
3da, 37%
3ba, 80%
3ca, 50%
O
Scheme 2. Regiosepecific C2 coupling of heterocycles with
O
O
O
O
O
inactive C(sp3)−H bond. a
S
S
O
O
O
O
O
CuI (20 mol %),
3ha, trace
3ea, 81%
3fa, 54%
3ga, 51%
Xphos (20 mol %)
H
H
+
O
O
O
DTBP (3 equiv.),
120 C, 24 h
O
X
O
O
R
NC
NC
R
O
O
O
O
O
O
O
O
S
3
1
2
O
O
O
O
O
O
O
3la, trace
3ja, 66%
3ka, 41%
3ia, 65%
+
O
O
O
O
O
O
Br
O
O
S
S
3ab1 : 3ab
2, 80% (3 : 2)
3ac
, 58%
O
S
O
S
O
O
O
O
NC
O
O
O
O
O
O
Br
O
Cl
3ma, 41%
3oa
3pa
, 62%
, 44%
3na, 50%
O
O
O
O
O
3cc, 66%
3ic
, 56%
3ad, 81%
S
O
O
S
O
NC
O
O
O
O
+
O
O
O
O
O
O
O
O
O
3id, 61%
3jd, 63%
3qa1 : 3qa2, 85% (48 : 37)
3cd, 70%
a Reaction conditions: 1a (0.25 mmol), catalyst (20 mol %), additive
(20 mol %), oxidant (3 equiv.), cyclic ethers (1.5 mL), in a sealed
tube under N2 at 120 oC (oil bath) for 24 h, isolated yield.
O
S
O
O
O
O
S
O
O
S
O
S
+
O
O
O
3ra, 65%
3sa, 73%
To gain insights into the mechanism of this transformation,
some control experiments were performed using THF under the
modified conditions (Scheme 3). The strong deuterium kinetic
isotope effect (KH/D = 3.3) indicated that the C(sp3)-H bond
cleavage of THF might be the rate-determining step. When 2.0
equivalent of TEMPO was added as a radical inhibitor, no target
product was obtained. Two strong molecular ion peaks (m/z =
228.1963 and m/z = 539.2869) were detected and attributed to
[TEMPO-THF+H]+ (Exact mass: 228.1958) and [Cu-Xphos]+
(m/z = 539.2869). In order to further clarify the role of the copper
3ta1 : 3ta2, 62% (18 : 13)
O
O
O
O
S
N
O
N
S
O
H3COOC
O
N
S
O
O
3ua, 86%
3va, 66%
3wa, 73%
3xa
, 70%
a Reaction conditions: 1a (0.25 mmol), catalyst (20 mol %), additive
(20 mol %), oxidant (3 equiv.), 1,4-dioxane (1.5 mL), in a sealed
tube under N2 at 120 oC (oil bath) for 24 h, isolated yield.
Having established optimal reaction conditions, the substrate
scope of this copper-catalyzed alkylation of heteroaryls with 1,4-
dioxane was investigated (Scheme 1). In gerenal, all tested
heteroaryls were able to tolerate this catalyzed system, affording
the desired products in mediate to good yields. 4- or 5-
Methoxybenzofurans were smoothly transformed into the
corresponding products 3ba and 3ea in good yields. Only 50% of
5-bromobenzofuran was converted into product 3ca. Despite the
steric hindrance of 3-methylbenzofuran, the desired product 3da
was also isolated in 37%. Comparing with benzofuran (1a), the
reaction activity of benzothiophenes 1f and 1g was decreased,
and the target products 3af and 3ag were generated in moderate
yields. In addition, furans and thiophenes with electron-
withdrawing groups (-CN, -COOMe, -COMe and halogen) could
smoothly proceed this alkylation to give the corresponding
products (31a-3ka, 3ma-3pa) in satisfactory yields. However,
only a trace amount of products were detected from the reaction
of furan/thiophene with electron-rich groups (3ha and 3la). Aryl
substituted thiophenes reacted with 1,4-dioxane to give 3ra and
3sa in moderate yields. The substrates containing two reactive-
sites (1q and 1t) could be transformed into mono- and di-
substituted products with moderate to high conversation (3qa1,
3qa2, 3ta1 and 3ta2). To expand the scope of this methodology,
o
salt, the complex of CuI-Xphos was synthesized at 120 C in
THF (analyzed by ESI-MS). The target product could be
Scheme 3. Control experiments.
obtained in a higher yield 90% with this copper salts as a catalyst.
This result indicates the following: 1) a radical process might be
involved in this reaction; 2) complex [CuI-Xphos] may be the
catalytically active species.

Based on the above experimental results and literatures,11 two
possible mechanism pathways for copper-catalyzed CDC
reaction were presented (Scheme 4). Initially, the radical initiator
4.2 Experimental procedure for C-H alkylation of
heterocycles
ACCEPTED MANUSCRIPT
¯
DTBP was decomposed by copper complex ([Cu-L]+ or CuI2 ) to
To a reaction tube were added 20 mol % CuI, 20 mol % KI (or
X-phos), 0.25 mmol heterocycles, 3.0 equiv. DTBP, and 1.5 mL
cyclic ethers under a nitrogen atmosphere. The resulting mixture
was heated at 120 °C. After 24 hours, the solvent was removed
under vacuum, and the residue was purified by flash
chromatography (SiO2, petroleum ether/ethyl acetate =10:1).
give tert-butylperoxy radical A and generate [tBuO-Cu-L]2+ or
[tBuO-CuI2]-. Then, the radical A abstracted the C(sp3)-H
adjacent to the oxygen atom of ethers leading to the formation of
radical B or D, which would be further oxidized through a SET
(single-electron-transfer) step convert to the corresponding
oxonium cation C or E. Finally, addition of oxonium cation C or
E to the C-C bond of heterocycle results in the formation of the
target product 3aa or 3ad, and [tBuO-Cu-L]2+ and [tBuO-CuI2]-
were reduced to afford [Cu-L]+ or [CuI2]- for further cycle.
5. 4.3 Characterization data
2-(1,4-dioxan-2-yl)benzofuran (3aa).9f White solid (83%); Mp
1
56-57 °C; H NMR (400 MHz, CDCl3): δ 7.28 (d, J = 1.2 Hz,
1H), 2.61 (d, J = 1.6 Hz, 1H), 7.24-7.20 (m, 2H), 6.70 (s, 1H),
4.82 (dd, J = 9.2, 2.8 Hz, 1H), 4.04 (dd, J = 7.6, 2.8 Hz, 1H),
3.97-3.90 (m, 3H), 3.89-3.75 (m, 2H). 13C NMR (100 MHz,
CDCl3): δ 154.7, 153.8, 127.7, 124.4, 122.8, 121.1, 111.3, 104.4,
71.5, 69.2, 66.5, 66.4. HRMS (ESI) calcd. for C12H13O3 (M+H+):
205.0859, found: 205.0860.
Scheme 4. Proposed mechanism.
2-(1,4-dioxan-2-yl)-5-methoxybenzofuran (3ba). White solid
1
(80%); Mp 86-87 °C; H NMR (400 MHz, CDCl3): δ 7.36-7.34
(d, J = 8.8 Hz, 1H), 7.00 (d, J = 4.0 Hz, 1H), 6.88 (dd, J = 10.6,
5.0 Hz, 1H), 6.63 (s, 1H), 4.78 (dd, J = 9.6, 2.8 Hz, 1H), 4.02
(dd, J = 11.6, 2.8 Hz, 1H), 3.96-3.88 (m, 2H), 3.86-3.73 (m, 6H).
13C NMR (100 MHz, CDCl3): δ 155.9, 154.5, 149.7, 128.3,
113.3, 111.7, 104.5, 103.5, 71.5, 69.2, 66.5, 66.4, 55.8. HRMS
(ESI) calcd. for C13H15O4 (M+H+): 235.0965, found: 235.0965.
5-bromo-2-(1,4-dioxan-2-yl)benzofuran (3ca). White solid
(50%); Mp 36-37 °C; 1H NMR (400 MHz, CDCl3): δ 7.67 (d, J =
1.6 Hz, 1H), 7.39-7.32 (m, 2H), 6.65 (s, 1H), 4.80 (dd, J = 9.4,
2.8 Hz, 1H), 4.04 (dd, J = 11.5, 2.8 Hz, 1H). 13C NMR (100
MHz, CDCl3): δ 155.3, 153.5, 129.8, 127.4, 123.8, 116.0, 112.8,
103.9, 71.4, 69.2, 66.5, 66.4. HRMS (ESI) calcd. for C12H12BrO3
(M+H+): 282.9964, found: 282.9966.
2-(1,4-dioxan-2-yl)-3-methylbenzofuran (3da). Yellow oil
1
(37%); H NMR (400 MHz, CDCl3): δ 7.49 (d, J = 4.0 Hz, 1H),
7.47 (d, J = 4.0 Hz, 1H), 7.30-7.20 (m, 2H), 4.86 (dd, J = 10.2,
4.0 Hz, 1H), 4.01 (dd, J = 11.8, 10.2 Hz, 1H), 3.97-3.90 (m, 2H),
3.89-3.84 (m, 1H), 3.83-3.78 (m, 2H), 2.28 (s, 3H). 13C NMR
(100 MHz, CDCl3): δ 154.2, 148.2, 129.4, 124.6, 122.4, 119.5,
114.0, 111.2, 70.4, 69.0, 67.1, 66.3, 57.8. HRMS (ESI) calcd. for
C13H15O3 (M+H+): 209.1016, found: 209.1016.
3. Conclusion
In summary, we have developed an efficient Cu-catalyzed
CDC reaction of heteroaryls with cyclic ethers. Various
(benzo)furans and (benzo)thiophenes were well able to tolerate
this methodology to give the corresponding desired products in
moderate to good yields. Under the results of the experiments for
mechanism study, we proposed that this reaction might proceed
through a radical process.
2-(1,4-dioxan-2-yl)-7-methoxybenzofuran (3ea). Yellow oil
1
(81%); H NMR (400 MHz, CDCl3): δ 7.14 (s, 1H), 7.13 (d, J =
1.4 Hz, 1H), 6.79-6.77 (m, 1H), 6.69 (s, 1H), 4.82 (dd, J = 9.6,
2.8 Hz, 1H), 4.06 (dd, J = 11.2, 2.8 Hz, 1H), 3.98 (s, 3H), 3.90
(dd, J = 5.6, 2.4 Hz, 1H), 3.87-3.84 (m, 1H), 3.82-3.74 (m, 3H).
13C NMR (100 MHz, CDCl3): δ 154.1, 145.3, 143.9, 129.4,
123.5, 113.3, 106.4, 104.5, 71.4, 69.3, 66.4, 66.3, 55.8. HRMS
(ESI) calcd. for C13H15O4 (M+H+): 235.0965, found: 235.0969.
4. Experimental
4.1 General
All reactions were run under nitrogen in Schlenk tubes using
vacuum lines. 1,4-Dioxane analytical grade and THF were
distilled before use. Chemical reagents were purchased from
commercial suppliers and used without further purification. NMR
spectra were recorded at 400 MHz (1H) and 100 MHz (13C) using
TMS as an internal standard. Chemical shifts are given relative to
2-(benzo[b]thiophen-2-yl)-1,4-dioxane (3fa). White solid
1
(54%); Mp 79-80 °C; H NMR (400 MHz, CDCl3): δ 7.83-7.80
(m, 1H), 7.72 (dd, J = 14.0, 7.0 Hz, 1H), 7.35-7.28 (m, 2H), 7.21
(s, 1H), 4.94 (dd, J = 9.6, 3.2 Hz, 1H), 4.00 (dd, J = 11.6, 2.8 Hz,
1H), 3.96-3.91 (m, 2H), 3.88-3.70 (m, 3H), 3.66 (dd, J = 11.6,
2.8 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 168.9, 153.0, 134.5,
126.1, 125.1, 123.1, 121.7, 75.4, 70.5, 66.9, 66.4. HRMS (ESI)
calcd. for C12H13O2S (M+H+): 221.0631, found: 221.0631.
CDCl3 (7.26 ppm for H NMR, 77 ppm for 13C NMR). The
1
following abbreviations were used to explain the multiplicities: s
= singlet, d = doublet, dd = doublet of doublet, t = triplet, q =
quartet. Melting points are uncorrected (by Yuhua X-5). High
resolution mass spectra (HRMS) were obtained on an Agilent
LC-MSD-Trap-XCT spectrometer with micromass MS software
using electrospray ionisation (ESI).
2-(5-methylbenzo[b]thiophen-2-yl)-1,4-dioxane (3ga). White
1
solid (51%); Mp 126-127 °C; H NMR (400 MHz, CDCl3): δ
7.68 (d, J = 8.0 Hz, 1H), 7.51 (s, 1H), 7.14-7.12 (m, 2H), 4.94-
4.90 (m, 1H), 4.06-3.86 (m, 2H), 3.84-3.71 (m, 3H), 3.66 (dd, J =
11.6, 9.8Hz, 1H), 2.44 (s, 3H). 13C NMR (100 MHz, CDCl3): δ

4
Tetrahedron
ACCEPTED MANUSCRIPT
161.6, 150.5, 140.5, 125.5, 124.6, 120.4, 110.8, 71.0, 68.4,
5,7-di(1,4-dioxan-2-yl)-2,3-dihydrothieno[3,4-b][1,4]dioxine
66.5, 66.4. HRMS (ESI) calcd. for C13H15O2S (M+H+): 235.0787,
found: 235.0788.
(3qa2). Brown solid (37%); Mp 61-62 °C;1H NMR (400 MHz,
CDCl3): δ 4.89 (dd, J = 10.0, 3.0 Hz, 1H), 4.82 (dd, J = 9.8, 2.8
Hz, 1H), 4.19 (s, 4H), 3.90-3.80 (m, 6H), 3.75-3.64 (m, 4H),
3.61-3.54 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 162.5, 148.4,
133.1, 132.8, 124.7, 73.6, 72.0, 66.8, 66.3, 52.1. HRMS (ESI)
calcd. for C14H19O6S (M+H+): 315.0897, found: 315.0899.
5-(1,4-dioxan-2-yl)furan-2-carbonitrile (3ia). Yellow oil
1
(65%); H NMR (400 MHz, CDCl3): δ 7.07-7.06 (d, J = 3.6 Hz,
1H), 6.47 (dd, J = 3.6, 0.4 Hz, 1H), 4.70 (dd, J = 9.3, 2.8 Hz,
1H), 3.98 (dd, J = 11.6, 2.8 Hz, 1H), 3.91-3.90 (m, 2H), 3.91-
3.83 (m, 2H), 3.81-3.77 (m, 1H), 3.75-3.69 (m, 2H). 13C NMR
(100 MHz, CDCl3): δ 156.8, 125.9, 122.6, 111.2, 109.2, 70.7,
68.9, 66.4. HRMS (ESI) calcd. for C9H10NO3 (M+H+): 180.0655,
found: 180.0657.
2-(5-phenylthiophen-2-yl)-1,4-dioxane (3ra). Yellow oil
(65%); H NMR (400 MHz, CDCl3): δ 7.44-7.34 (m, 5H), 7.33
1
(d, J = 5.0 Hz, 1H), 7.06 (d, J = 5.0 Hz, 1H), 4.94 (dd, J = 10.0,
2.8 Hz, 1H), 3.93-3.90 (m, 1H), 3.86-3.80 (m, 2H), 3.77-3.73 (m,
2H), 3.65 (dd, J =11.6, 10.0 Hz, 1H). 13C NMR (100 MHz,
CDCl3): δ 141.0, 136.1, 135.2, 129.1, 128.8, 128.6, 127.4, 124.8,
72.2, 72.2, 66.9, 66.3. HRMS (ESI) calcd. for C14H15O2S
(M+H+): 247.0787, found: 247.0787.
methyl 5-(1,4-dioxan-2-yl)furan-2-carboxylate (3ja). White
1
solid (66%); Mp 74-75 °C; H NMR (400 MHz, CDCl3): δ 7.14
(d, J = 4.0 Hz, 1H), 6.45 (d, J = 4.0 Hz, 1H), 4.72 (dd, J = 9.6,
2.8 Hz, 1H), 3.99 (dd, J = 12.0, 2.8 Hz, 1H), 3.92-3.84 (m, 5H),
3.77-3.69 (m, 3H). 13C NMR (100 MHz, CDCl3): δ 158.9, 155.6,
144.2, 118.5, 109.5, 71.0, 69.1, 66.4, 66.3, 51.8. HRMS (ESI)
calcd. for C10H13O5 (M+H+): 213.0757, found: 213.0760.
2-(5-(4-methoxyphenyl)thiophen-2-yl)-1,4-dioxane
(3sa).
Green oil (73%); Mp 103-104 °C; 1H NMR (400 MHz, CDCl3): δ
7.49 (d, J = 8.6 Hz, 1H), 7.05 (d, J = 4.0 Hz, 1H), 6.93-6.88 (m,
3H), 4.83 (d, J = 9.8, 2.4 Hz, 1H), 3.97-3.91 (m, 2H), 3.89-3.84
(m, 1H), 3.82 (s, 3H), 3.80-3.76 (m, 2H), 375-3.68 (m, 1H), 3.64
(dd, J = 11.6, 9.8 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 159.3,
144.2, 139.0, 127.1, 127.0, 125.6, 121.5, 114.3, 73.8, 72.1, 66.9,
66.3, 55.3, 55.3. HRMS (ESI) calcd. for C15H17O3S(M+H+):
277.0893, found: 277.0900.
1-(5-(1,4-dioxan-2-yl)furan-2-yl)ethanone (3ka). Yellow oil
1
(41%); H NMR (400 MHz, CDCl3): δ 7.14 (d, J = 3.6 Hz, 1H),
6.48 (d, J = 3.6 Hz, 1H), 6.73 (dd, J = 8.8, 2.8 Hz, 1H), 4.03-3.85
(m, 3H), 3.83-3.70 (m, 3H), 2.46 (s, 3H). 13C NMR (100 MHz,
CDCl3): δ 186.5, 155.8, 152.4, 117.8, 109.9, 71.1, 69.1, 66.4,
66.3, 25.9. HRMS (ESI) calcd. for C10H13O4 (M+H+): 197.0808,
found: 197.0810.
2-(4-phenylthiophen-2-yl)-1,4-dioxane (3ta1). Yellow oil
1
(36%); H NMR (400 MHz, CDCl3): δ 7.44-7.33 (m, 5H), 7.32
5-(1,4-dioxan-2-yl)thiophene-2-carbonitrile (3ma). Yellow oil
(d, J = 5.2 Hz, 1H), 7.06 (d, J = 5.2 Hz, 1H), 4.93 (dd, J = 9.8,
2.8 Hz, 1H), 3.91 (d, J = 11.2 Hz, 1H), 3.86-3.78 (m, 2H), 3.75-
3.73 (m, 2H), 3.65 (dd, J = 11.6, 9.8 Hz, 1H). 13C NMR (100
MHz, CDCl3): δ 141.0, 136.1, 135.2, 129.1, 128.8, 128.6, 127.4,
124.8, 72.3, 72.2, 66.9, 66.3. HRMS (ESI) calcd. for C14H15O2S
(M+H+): 247.0787, found: 247.0796.
1
(41%); H NMR (400 MHz, CDCl3): δ 7.51 (d, J = 4.0 Hz, 1H),
6.95 (dd, J = 4.0, 0.8 Hz, 1H), 4.89 (d, J = 10.4, 3.0 Hz, 1H),
3.97-3.87 (m, 3H), 3.85-3.76 (m, 1H), 3.74-3.69 (m, 1H), 3.54-
3.48 (m, 1H). 13C NMR (100 MHz, CDCl3): δ 149.4, 137.2,
124.1, 114.2, 109.2, 73.3, 71.8, 66.9, 66.3. HRMS (ESI) calcd.
for C9H10NO2S (M+H+): 196.0427, found: 196.0429.
2,2'-(3-phenylthiophene-2,5-diyl)bis(1,4-dioxane)
(3ta2).
methyl 5-(1,4-dioxan-2-yl)thiophene-2-carboxylate (3na).
White solid (50%); Mp 88-89 °C; 1H NMR (400 MHz, CDCl3): δ
7.68 (d, J = 3.7 Hz, 1H), 6.96 (dd, J = 3.8, 0.8 Hz, 1H), 4.86 (dd,
J = 9.6, 2.8 Hz, 1H), 3.94 (dd, J = 11.6, 2.8 Hz, 2H), 3.91-3.85
(m, 4H), 3.81-3.78 (m, 1H), 3.75-3.68 (m, 1H), 3.55 (dd, J =
11.6, 9.8 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 162.5, 148.4,
133.1, 132.7, 124.7, 73.6, 72.0, 66.8, 66.3, 52.1. HRMS (ESI)
calcd. for C10H13O4S (M+H+): 229.0529, found: 229.0531.
1
White solid (26%); Mp 93-94 °C; H NMR (400 MHz, CDCl3): δ
7.43-7.39 (m, 2H), 7.36-7.32 (m, 3H), 6.97-6.95 (m, 1H), 4.39-
4.80 (m, 2H), 3.96-3.89 (m, 4H), 3.86-3.77 (m, 3H), 3.75-3.69
(m, 3H), 3.68-3.59 (m, 2H). 13C NMR (100 MHz, CDCl3): δ
140.7, 140.6, 140.0, 139.9, 135.8, 135.8, 135.1, 134.9, 128.7,
128.7, 128.6, 128.6, 127.5, 127.5, 126.9, 126.3, 73.8, 73.4, 72.3,
72.2, 72.1, 72.0, 71.8, 67.0, 66.9, 66.8, 66.7, 66.6, 66.3. HRMS
(ESI) calcd. for C18H21O4S (M+H+): 333.1155, found: 333.1163.
methyl 3-chloro-5-(1,4-dioxan-2-yl)thiophene-2-carboxylate
(3oa). White solid (62%); Mp 52-53 °C; H NMR (400 MHz,
2-(thieno[3,2-b]thiophen-2-yl)-1,4-dioxane (3ua). Black solid
(86%); Mp 36-37 °C; 1H NMR (400 MHz, CDCl3): δ 7.34 (d, J =
5.2 Hz, 1H), 7.22 (dd, J = 5.4, 1.6 Hz, 1H), 7.17 (s, 1H), 4.88
(dd, J = 9.7, 2.6 Hz, 1H), 3.96 (dd, J = 11.6, 2.8 Hz, 1H), 3.93-
3.85 (m, 2H), 3.82-3.70 (m, 2H), 3.65 (dd, J = 12.0, 9.8 Hz, 1H).
13C NMR (100 MHz, CDCl3): δ 142.9, 138.8, 138.5, 127.1,
119.5, 117.0, 74.1, 72.1, 66.9, 66.4. HRMS (ESI) calcd. for
C10H11O2S2 (M+H+): 227.0195, found: 227.0196.
1
CDCl3): δ 6.88 (d, J = 0.8 Hz, 1H) 3.79 (d, J = 9.8, 2.8 Hz, 1H),
3.92 (dd, J = 11.6, 2.8 Hz, 2H), 3.89-3.83 (m, 4H), 3.81-3.78 (m,
1H), 3.73-3.66 (m, 2H), 3.50 (dd, J = 11.6, 9.8 Hz, 1H). 13C
NMR (100 MHz, CDCl3): δ 160.9, 146.2, 130.8, 126.6, 124.7,
73.1, 71.6, 66.7, 66.2, 52.1. HRMS (ESI) calcd. for C10H12ClO4S
(M+H+): 263.0139, found: 263.0141.
2-(4,5-dibromothiophen-2-yl)-1,4-dioxane (3pa). Yellow oil
(44%); H NMR (400 MHz, CDCl3): δ 6.78 (d, J = 0.8 Hz, 1H),
2-(1,4-dioxan-2-yl)benzo[d]oxazole (3va). White solid (66%);
Mp 60-61 °C; 1H NMR (400 MHz, CDCl3): δ 7.76-7.71 (m, 1H),
7.57-7.52 (m, 1H), 7.38-7.32 (m, 2H), 4.97 (dd, J =9.0, 2.8 Hz,
1H), 4.20 (d, J = 11.6, 2.8 Hz, 1H), 4.08-3.90 (m, 3H), 3.87-3.77
(m, 2H). 13C NMR (100 MHz, CDCl3): δ 141.3, 138.7, 113.5,
98.8, 70.8, 70.6, 67.1, 66.3, 64.7, 64.6. HRMS (ESI) calcd. for
C11H12NO3 (M+H+): 206.0812, found: 206.0813.
1
4.80-4.76 (m, 1H), 3.92-3.86 (m, 3H), 3.84-3.80 (m, 1H), 3.79-
3.76 (m, 1H), 3.69-3.65 (m, 1H), 3.51 (dd, J = 11.8, 9.6 Hz, 1H).
13C NMR (100 MHz, CDCl3): δ 147.5, 127.1, 126.9, 119.7, 73.2,
71.6, 66.7, 66.2. HRMS (ESI) calcd. for C8H9Br2O2S (M+H+):
326.8685, found: 326.8688.
5-(1,4-dioxan-2-yl)-2,3-dihydrothieno[3,4-b][1,4]dioxine
(3qa1). Brown solid (48%); Mp 45-46 °C; H NMR (400 MHz,
2-(1,4-dioxan-2-yl)benzo[d]thiazole (3wa). Yellow solid
(73%); Mp 56-57 °C; 1H NMR (400 MHz, CDCl3): δ 8.00 (d, J =
7.8 Hz, 1H), 7.92-7.90 (m, 1H), 7.50-7.46 (m, 1H), 7.41-7.37 (m,
1H), 5.05 (d, J = 9.6, 3.0 Hz, 1H), 4.04-3.94 (m, 2H), 3.85-3.73
(m, 2H), 3.70 (dd, J = 11.6, 9.6 Hz, 1H). 13C NMR (100 MHz,
CDCl3): δ 138.3, 138.3, 112.7, 112.6, 70.8, 70.5, 70.4, 70.0, 66.9,
1
CDCl3): δ 6.30 (s, 1H), 4.87 (dd, J = 24.0, 12.0 Hz, 1H), 4.22-
4.16 (m, 4H), 3.91-3.83 (m, 3H), 3.77-3.67 (m, 2H), 3.61 (dd, J =
11.6, 9.8 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 160.9, 146.2,
130.9, 126.6, 124.7, 73.1, 71.6, 66.7, 66.2, 52.1. HRMS (ESI)
calcd. for C10H13O4S (M+H+): 229.0529, found: 229.0530.

66.8, 66.2, 66.2, 64.7, 64.7. HRMS (ESI) calcd. for C11H12NO2S
73.3, 67.6, 54.9, 29.6, 24.8. HRMS (ESI) calcd. for C13H15O3
(M+H+): 219.1016, found: 219.1017.
ACCEPTED MANUSCRIPT
(M+H+): 222.0583, found: 222.0579.
methyl
5-(1,4-dioxan-2-yl)-1-methyl-1H-pyrrole-2-
5-(tetrahydrofuran-2-yl)furan-2-carbonitrile (3id). Yellow oil
(56%); H NMR (400 MHz, CDCl3): δ 7.03 (d, J = 3.6 Hz, 1H),
carboxylate (3xa). White solid (70%); Mp 101-102 °C; 1H NMR
(400 MHz, CDCl3): δ 6.89 (d, J = 3.8 Hz, 1H), 6.11 (d, J = 3.8
Hz, 1H), 4.62 (dd, J = 9.3, 2.6 Hz, 1H), 3.98 (dd, J = 11.4, 2.6
Hz, 1H), 3.95 (s, 3H), 3.89-3.83 (m, 3H), 3.81-3.77 (m, 3H),
3.74-3.67 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 161.7, 135.8,
123.5, 116.9, 107.2, 69.6, 69.1, 66.5, 66.3, 51.1, 32.8. HRMS
(ESI) calcd. for C11H16NO4 (M+H+): 235.0965, found: 235.0969.
1
6.36 (d, J = 3.4 Hz, 1H), 4.94 (dd, J = 7.0, 5.2 Hz, 1H), 4.03-3.97
(m, 1H), 3.93-3.88 (m, 1H), 2.31-2.22 (m, 1H), 2.12-1.97 (m,
3H). 13C NMR (100 MHz, CDCl3): δ 161.5, 125.5, 122.7, 111.6,
107.8, 73.7, 68.8, 30.9, 25.8. HRMS (ESI) calcd. for C9H10NO2
(M+H+): 164.0706, found: 164.0705.
methyl 5-(tetrahydrofuran-2-yl)furan-2-carboxylate (3jd).
Yellow oil (63%); 1H NMR (400 MHz, CDCl3): δ 7.12 (d, J = 3.6
Hz, 1H), 6.35 (d, J = 3.6 Hz, 1H), 4.98 (m, 1H), 4.04-3.99 (m,
1H), 3.93-3.90 (m, 1H), 3.87 (s, 3H), 2.31-2.23 (m, 1H), 2.15-
2.07 (m, 1H), 2.05-1.97 (m, 2H). 13C NMR (100 MHz, CDCl3): δ
160.3, 159.2, 143.8, 118.8, 108.2, 74.0, 68.7, 51.8, 51.8, 31.0,
25.7. HRMS (ESI) calcd. for C10H13O4 (M+H+): 197.0808,
found:197.0813.
1
2-(1,3-dioxolan-2-yl)benzofuran (3ab1). Yellow oil (48%); H
NMR (400 MHz, CDCl3): δ 7.57-7.55 (m, 1H), 7.50-7.48 (m,
1H), 7.31-7.27 (m, 1H), 7.24-7.20 (m,1H), 6.80 (s, 1H), 6.08 (s,
1H), 4.20-4.14 (m, 2H), 4.10-4.05 (m, 2H). 13C NMR (100 MHz,
CDCl3): δ 155.2, 153.5, 127.5, 124.9, 122.9, 121.5, 111.7, 105.3,
98.0, 65.4. HRMS (ESI) calcd. for C11H11O3 (M+H+): 191.0703,
found: 191.0705.
1
2-(1,3-dioxolan-4-yl)benzofuran (3ab2). Yellow oil (32%); H
Acknowledgements
NMR (400 MHz, CDCl3): δ 7.55-7.53 (m, 1H), 7.48-7.45 (m,
1H), 7.30-7.26 (m, 1H), 7.24-7.20 (m,1H), 6.73 (s, 1H), 5.20 (s,
1H), 5.20-5.17 (t, J = 12.0 Hz, 1H), 5.11 (s,1H), 4.25 (dd, J = 8.2,
7.1 Hz, 1H), 4.12 (dd, J = 8.2, 6.0 Hz, 1H). 13C NMR (100 MHz,
CDCl3): δ 155.2, 154.6, 127.8, 124.6, 122.9, 121.2, 111.4, 104.9,
95.8, 71.2, 68.5. HRMS (ESI) calcd. for C11H11O3 (M+H+):
191.0703, found: 191.0699.
We are grateful to the National Natural Science Foundation of
China (21172200 and 21302172) for financial support to this
research.
Supplementary data
Supplementary data associated with this article can be found in
the online version, at XXX.
2-(tetrahydro-2H-pyran-2-yl)benzofuran (3ac). Yellow oil
(58%); H NMR (400 MHz, CDCl3): δ 7.53-7.51 (m, 1H), 7.47-
1
7.45 (m, 1H), 7.26-7.16 (m, 2H), 6.61 (s, 1H), 4.53 (dd, J = 10.6,
2.0 Hz, 1H), 4.13-4.10 (m, 1H), 3.68-3.61 (m, 1H), 1.99-1.85 (m,
3H), 1.75-1.57 (m, 3H). 13C NMR (100 MHz, CDCl3): δ 157.9,
154.8, 128.1, 124.1, 122.6, 121.0, 111.3, 102.7, 73.5, 68.8, 29.9,
25.7, 23.1. HRMS (ESI) calcd. for C13H15O2 (M+H+): 103.1067,
found: 103.1068.
References and notes
1.
(a) Rainier, J. D. Synthesis of Saturated Oxygenated Heterocycles I;
Springer-Verlag Berlin Heidelberg; 2014, pp 1-44; (b) Zhang, S.;
Zhang, F. and Tu, Y. Chem. Soc. Rev. 2011, 40, 1937.
2.
For selected reviews on C–H bond functionalization, see: (a) Yeung, C.
S. and Dong, V. M. Chem. Rev. 2011, 111, 1215; (b) Liu, C.; Zhang,
H.; Shi, W. and Lei, A. Chem. Rev. 2011, 111, 1780; (c) Yamaguchi, J.;
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5-methoxy-2-(tetrahydro-2H-pyran-2-yl)benzofuran
(3cc).
1
Yellow oil (66%); Mp 86-87 °C; H NMR (400 MHz, CDCl3): δ
7.35 (d, J = 8.6 Hz, 1H), 6.99 (d, J = 8.6 Hz, H), 1H), 6.86-6.83
(m, 1H), 6.55 (s, 1H), 4.52 (dd, J = 17.0, 8.6 Hz, 1H), 3.82 (s,
3H), 3.68-3.62 (m, 1H), 1.99-1.94 (m, 1H), 1.92-1.84 (m, 1H),
1.75-1.58 (m, 3H). 13C NMR (100 MHz, CDCl3): δ 158.6, 155.8,
149.7, 128.6, 112.7, 111.7, 103.5, 102.9, 73.5, 68.8, 55.9, 55.9,
29.9, 25.7, 23.1. HRMS (ESI) calcd. for C14H17O3 (M+H+):
233.1172, found: 233.1175.
3.
(a) Zhang, Y. and Li, C. Angew. Chem., Int. Ed. 2006, 45, 1949; (b)
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4.
5.
5-(tetrahydro-2H-pyran-2-yl)furan-2-carbonitrile
(3ic).
Yellow oil (56%); 1H NMR (400 MHz, CDCl3): δ 7.04 (d, J = 3.6
Hz, 1H), 6.37 (d, J = 3.6 Hz, 1H), 4.42 (dd, J = 11.0, 2.1 Hz, 1H),
4.09-4.05 (m, 1H), 3.63-3.57 (m, 1H), 1.98-1.88 (m, 2H), 1.80-
1.57 (m, 5H). 13C NMR (100 MHz, CDCl3): δ 160.8, 125.3, 12.7,
111.6, 107.5, 72.9, 68.8, 29.9, 25.5, 22.9. HRMS (ESI) calcd. for
C10H12NO2 (M+H+): 178.0863, found: 178.0869.
6.
7.
(a) Chen, L.; Shi, E.; Liu, Z.; Chen, S.; Wei, W.; Li, H.; Xu, K. and
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2-(tetrahydrofuran-2-yl)benzofuran (3ad). Yellow oil (81%);
1H NMR (400 MHz, CDCl3): δ 7.51-7.49 (m, 1H), 7.45-7.43 (m,
1H), 7.25-7.16 (m, 2H), 6.60 (s, 1H), 5.05 (t, J = 13.5 Hz, 1H),
4.07-4.02 (m, 1H), 3.94-3.89 (m, 2H), 2.30-2.14 (m, 2H). 13C
NMR (100 MHz, CDCl3): δ 158.2, 155.1, 128.2, 124.0, 122.7,
120.9, 111.3, 103.0, 74.4, 68.7, 30.7, 25.9. HRMS (ESI) calcd.
for C12H13O2 (M+H+): 189.0910, found: 189.0912.
8.
For selected reports on C–H bond functionalization of heteroarenes,
see: (a) Pan, S.; Liu, J.; Li, H.; Wang, Z.; Guo, X. and Li, Z. Org. Lett.
2010, 12, 1932; (b) He, T.; Yu, L.; Zhang, L.; Wang, L. and Wang, M.
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Li, Z. J. Org. Chem. 2009, 74, 8848; (e) Xie, Z.; Cai, Y.; Hu, H.; Lin,
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Jin, J. and MacMillan, D. W. C. Angew. Chem., Int. Ed. 2015, 54, 1565;
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5-methoxy-2-(tetrahydro-2H-pyran-2-yl)benzofuran
(3cd).
Yellow oil (70%); 1H NMR (400 MHz, CDCl3): δ 7.32 (d, J = 8.6
Hz, 1H), 6.98 (d, J = 2.8 Hz, 1H), 6.85 (dd, J = 8.6, 2.8 Hz, 1H),
6.55 (s, 1H), 5.05 (t, J = 6.4 Hz, 1H), 4.07 (dd, J = 15.4, 7.8 Hz,
1H), 3.96-3.90 (m, 1H), 3.13 (s, 3H). 13C NMR (100 MHz,
CDCl3): δ 157.9, 154.8, 149.0, 127.7, 111.6, 110.6, 102.5, 102.2,

6
Tetrahedron
Liu, J. and Wang, L. Org. Biomol. Chem. 2015, 13, 4596; (k) Ambala,
ACCEPTED MANUSCRIPT
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