Copper-catalyzed hydroalkylation of alkynes: Addition of sp3 C-H bonds across carbon-carbon triple bonds

Article abstract of DOI:10.1055/s-0029-1216991

The regioselective copper-catalyzed addition of sp³ C-H bonds adjacent to an oxygen atom to various alkynes has been accomplished under mild reactions conditions in the presence of tertbutyl hydroperoxide to give the corresponding alkenylated p

Full text of DOI:10.1055/s-0029-1216991

3504
SPECIAL TOPIC
Copper-Catalyzed Hydroalkylation of Alkynes: Addition of sp3 C–H Bonds
Across Carbon–Carbon Triple Bonds
C
opper-Catalyz
e
ed Hydroal
h
kylation of
A
a
lkynes o Huang, Kai Cheng, Bangben Yao, Jinlong Zhao, Yuhong Zhang*
Department of Chemistry, Zhejiang University, Hangzhou 310027, P. R. of China
Fax +86(571)87953244; E-mail: yhzhang@zju.edu.cn
Received 29 March 2009
mild reaction conditions. This transformation represents
Abstract: The regioselective copper-catalyzed addition of sp3 C–H
bonds adjacent to an oxygen atom to various alkynes has been ac-
complished under mild reactions conditions in the presence of tert-
butyl hydroperoxide to give the corresponding alkenylated prod-
ucts.
the first example of the transition metal mediated hydro-
alkylation of an alkyne with an sp3 C–H bond.
Hydroalkylation is an important transformation in organic
synthesis. Moreover, metal-mediated addition of sp3 C–H
bonds to alkynes remains a difficult task. Our studies
started with the coupling of tetrahydrofuran and ethynyl-
benzene as shown in Table 1. It was found that the addi-
tive played an important role in the reaction. Benzoyl
peroxide, which proved to be an efficient additive for ac-
tivation of C–H bonds in phenylpyridines in our previous
studies,9 was completely inactive (Table 1, entry 1). How-
ever, a small amount of hydroalkylation product was ob-
tained using m-chloroperoxybenzoic acid (MCPBA)
(Table 1, entry 2), and the reaction yield was further im-
proved using other peroxides (Table 1, entries 3 and 4).
The optimal result was obtained using tert-butyl hydro-
peroxide as additive which afforded a 62% yield of prod-
uct (Table 1, entry 5). A trace amount of the desired
product was detected using the radical initiator 2,2¢-azo-
bis(isobutyronitrile) (AIBN). No reaction was observed
when 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)
and N-bromosuccinimide (NBS) were employed as addi-
tives (Table 1, entries 6–8). A number of catalysts includ-
ing salts of copper, silver and gold were able to promote
this transformation in the presence of tert-butyl hydroper-
oxide as additive (Table 1, entries 9–20); copper(I) bro-
mide demonstrated the best activity in comparison with
the other metals tested (Table 1, entry 5). An increased
loading of copper(I) bromide did not improve the reaction
yield further and higher loadings (>30 mol%) led to the
formation of the corresponding homocoupling product of
Key words: C–H activation, copper, addition reactions, alkynes,
tert-butyl hydroperoxide
Considerable effort has been devoted to selective C–H
bond activation,1 and important progress has been
achieved in transition metal catalyzed activation of sp2
C–H bonds which has provided promising economical al-
ternatives to traditional organic chemistry.2 Activation of
an sp3 C–H bond, however, is expected to be more diffi-
cult since cleavage of an sp3 C–H bond is kinetically and
thermodynamically unfavorable. Recent studies estab-
lished that sp3 C–H bonds adjacent to a heteroatom such
as nitrogen, oxygen or sulfur were more reactive than
those next to carbon atoms, and some promising catalytic
systems have been reported for sp3 C–H bond cleavage.3
For example, Murai and co-workers pioneered the ruthe-
nium-catalyzed addition of sp3 C–H bonds adjacent to a
nitrogen atom in alkylamines to alkenes.4 The intramolec-
ular catalytic cyclization of alkene–amide substrates in
the presence of iridium complexes via cross-coupling of
an sp3 C–H bond adjacent to a nitrogen atom with an alk-
ene moiety was reported by Sames and co-workers.5 On
the other hand, direct conversions of sp3 C–H bonds adja-
cent to heteroatoms into C–C bonds using activated meth-
ylene compounds, alkenes or alkynes via cross-
dehydrogenative coupling (CDC) have been developed by
Li and others.6 Oxygen-containing compounds are of sig-
nificant interest in industrial and academic research. How-
ever, in contrast to cleavage of C–H bonds adjacent to
nitrogen, examples of activation of C–H bonds next to ox-
ygen atoms are limited because of its higher oxidation po-
tential. Although cleavage of the benzylic C–H bond of
benzyl ethers has been reported by Li and Zhang,7 activa-
tion of a C–H bond adjacent to oxygen in an alkoxy group,
which is less active, is not common.8 Herein, we report the
copper-catalyzed addition of sp3 C–H bonds adjacent to
the oxygen atom of tetrahydrofuran with various alkynes
in the presence of tert-butyl hydroperoxide (TBHP) under
ethynylbenzene.
Chloro(triphenylphosphine)gold(I)
(PPh3AuCl) proved to be an efficient additive giving a
56% yield of product, however, the use of sodium tetra-
chloroaurate(III) dihydrate (NaAuCl4·2H2O) (10 mol%)
delivered a mixture of cross-coupling (25% yield) and ho-
mocoupling products whilst hydrogen tetrachloroau-
rate(III) tetrahydrate (HAuCl4·4H2O) was inactive
(Table 1, entries 18–20). Copper(I) bromide, being the
more efficient and cheaper catalyst, was employed in sub-
sequent experiments. Previous investigations on copper(I)
bromide catalyzed reactions of alkynes with sp3 C–H
bonds adjacent to a nitrogen atom demonstrated that alky-
nylation occurred via a cross-dehydrogenative coupling
process in the presence of tert-butyl hydroperoxide to give
the corresponding propargylamines as the major prod-
ucts.10 Thus it is apparent that the reactivity of a C–H bond
SYNTHESIS 2009, No. 20, pp 3504–3510
x
x.
x
x
.
2
0
0
9
Advanced online publication: 03.09.2009
DOI: 10.1055/s-0029-1216991; Art ID: C03409SS
© Georg Thieme Verlag Stuttgart · New York

SPECIAL TOPIC
Copper-Catalyzed Hydroalkylation of Alkynes
3505
ated halide substituents which are useful for further func-
tionalization. The regioselectivity of these reactions was
different from those of metal-catalyzed hydroarylations of
terminal arylalkynes in which a-aryl substituted alkenes
were formed.11 The present hydroalkylation reaction af-
forded exclusively b-alkylated alkenes, and only mono-
alkenylated tetrahydrofurans were observed. Both cis and
trans alkenylated products were isolated with the cis iso-
mers predominating. 2-Ethynylpyridine proved to be less
reactive affording the trans stereoisomer as the sole hy-
droalkylation product (Table 2, entry 10). The reaction
with tetrahydrothiophene afforded a 30% yield of product
whilst pyrrolidine failed to give the desired adduct under
the same reaction conditions. Six-membered cyclic ethers
such as tetrahydro-2H-pyran and 1,4-dioxane gave the de-
sired products in low yields, and these were difficult to
purify.
Table 1 The Effect of Various Metal Salts and Additives on the
Hydroalkylation Reactiona
catalyst (10 mol%)
O
additive (1 equiv),
O
H
50 °C,12 h
Entry Catalyst
Additive
Yield (%)b
–
O
1
2
CuBr
CuBr
O
O
O
O
Cl
OH
<5
O
O
We also studied the hydroalkylation reaction with 1,3-di-
oxolane, a substrate in which there are two different C–H
bond environments next to oxygen. Under the conditions
described above, reactions with various phenyl acetylenes
occurred selectively via C–H bond activation at C-2 of
1,3-dioxolane to afford 2-alkenylated 1,3-dioxolanes 1a–
5a as the major products (Scheme 1). The observed by-
products 1b–5b (>5%) were identified as the adducts re-
sulting from reaction at C-4 of 1,3-dioxolane. Again, C–C
bond formation occurred at the least-substituted carbon of
the alkyne, and both cis and trans stereoisomers were ob-
tained. This reaction represents a useful method to
achieve formylation and aldehyde protection in a single
step.
O
3
4
CuBr
CuBr
32
29
O
t-Bu
O
t-Bu
O
5
6
CuBr
TBHP
AIBN
DDQ
62
<5
–
CuBr
7
CuBr
8
CuBr
NBS
–
9
CuCl
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
48
50
47
–
10
11
12
13
14
15
16
17
18
19
20
CuI
The exact mechanism of this addition reaction is not clear
at present. Since peroxides are the most common source
of spontaneously induced free radicals and transition met-
als such as copper(I) usually promote the generation of
such free radicals, it was assumed, initially, that a free-
radical process might be involved in this addition reac-
tion. We therefore envisaged that the addition of a free-
radical scavenger would suppress the hydroalkylation re-
action. To our surprise, the reaction was virtually unaf-
fected by the addition of one equivalent of the free-radical
scavenger, 2,6-di-tert-butyl-4-methylphenol (BHT). This
result highlights the unique activity of the copper catalyst
in mediating this reaction. A similar phenomenon was
also observed by Li and Zhao using the copper(I) bro-
mide/tert-butyl hydroperoxide catalytic system,6c thus in-
dicating that a radical pathway is unlikely. On the other
hand, tert-butyl hydroperoxide is crucial to the success of
the reaction. Copper(I) bromide alone did not catalyze this
reaction under the same conditions, however, tert-butyl
hydroperoxide without the copper catalyst gave the de-
sired products, albeit in lower yields (Table 2, entries 1–
11). Interestingly, the reaction with tert-butyl hydroper-
oxide alone was almost completely suppressed by the ad-
dition of 2,6-di-tert-butyl-4-methylphenol implicating the
possible involvement of free radical intermediates in the
absence of metals.12 Hence it appears that reactions with
and without metal catalysts proceed via different path-
Cu2O
CuBr2
CuO
31
29
–
Cu(OAc)2
Cu(OTf)2
AgOAc
AgNO3
NaAuCl4·2H2O
HAuCl4·4H2O
PPh3AuCl
–
22
25
–
56
a Ethynylbenzene (51 mg, 0.5 mmol), catalyst (0.05 mmol), additive
(1 equiv), TBHP (1–1.2 equiv, 0.10 mL, 5–6 M in decane), THF (10
mL), 50 °C, 12 h.
b Yield of isolated product.
adjacent to a nitrogen atom is very different from that of a
C–H bond next to an oxygen atom.
Terminal arylalkynes possessing electron-donating or
electron-withdrawing substitutents on the aryl ring gave
the corresponding hydroalkylated products in good yields
(Table 2, entries 2–8). The reaction conditions also toler-
Synthesis 2009, No. 20, 3504–3510 © Thieme Stuttgart · New York

3506
L. Huang et al.
SPECIAL TOPIC
Table 2 Scope of the Addition Reactiona
CuBr (10 mol%), 12 h
TBHP (1–1.2 equiv), 50 °C
+
O
Ar
O
Ar
H
Entry
Alkyne
Product
Yield (%)b
Yield (%)d
(cis/trans)c
(cis/trans)c
1
2
3
51 (60:40)
36 (58:42)
33 (59:41)
62 (60:40)
61 (58:42)
65 (59:41)
O
O
O
4
5
6
7
8
9
49 (59:41)
59 (59:41)
33 (61:39)
40 (54:46)
43 (73:27)
35 (55:45)
68 (59:41)
64 (59:41)
57 (59:41)
50 (54:46)
61 (73:27)
63 (56:44)
O
Et
Et
O
t-Bu
t-Bu
O
MeO
MeO
O
H11C5O
H11C5O
O
Br
Br
O
F
F
10
22 (0:100)
trace
26 (0:100)
30 (60:40)
O
S
N
N
11e
a Alkyne (51 mg, 0.5 mmol), CuBr (7 mg, 0.05 mmol), TBHP (0.10 mL, 5–6 M in decane), THF (10 mL), 50 °C (oil-bath temp), 12 h.
b Yield of isolated product in the absence of CuBr.
c cis/trans Ratios were determined by 1H NMR spectroscopy. The stereoisomers were isolated by silica gel column chromatography.
d Yield of isolated product in the presence of CuBr.
e Tetrahydrothiophone was used as the substrate.
Synthesis 2009, No. 20, 3504–3510 © Thieme Stuttgart · New York

SPECIAL TOPIC
Copper-Catalyzed Hydroalkylation of Alkynes
3507
O
O
O
O
R
H
R
O
R
O
H
O
a
b (<5%)
O
O
O
O
O
1a 53%
(cis/trans = 24:29)
2a 43%
(cis/trans = 17:26)
3a 51%
(cis/trans = 23:28)
O
O
O
O
Br
Et
4a 55%
(cis/trans = 23:32)
5a 49%
(cis/trans = 24:25)
Scheme 1 Reaction of 1,3-dioxolane with various alkynes and the structures of the major products obtained. Reagents and conditions: alkyne
(51 mg, 0.5 mmol), CuBr (7 mg, 0.05 mmol), TBHP (0.10 mL, 5–6 M in decane), 1,3-dioxolane (10 mL), 50 °C, 12 h. E:Z ratio in parentheses
as determined by 1H NMR spectroscopy.
2-[(Z)-2-Phenylethenyl]tetrahydrofuran (Table 2, Entry 1)12a
ways. Furthermore, the use of copper(I) bromide (10
mol%) and 2,6-di-tert-butyl-4-methylphenol (1 equiv) led
to the formation of the desired adducts in ca. 8% isolated
yields, thus revealing that tert-butyl hydroperoxide was
not absolutely essential for the copper-catalyzed reaction.
The metal-free reaction conditions are a highly desirable
advantage, however, the efficiency remains to be im-
proved.
1H NMR (400 MHz, CDCl3): d = 7.36–7.23 (m, 5 H), 6.59 (d,
J = 11.6 Hz, 1 H), 5.71 (dd, J = 11.4, 9.0 Hz, 1 H), 4.67 (q, J = 7.7
Hz, 1 H), 3.96 (q, J = 7.3 Hz, 1 H), 3.79 (dt, J = 7.8, 6.4 Hz, 1 H),
2.18–2.10 (m, 1 H), 2.06–1.87 (m, 2 H), 1.74–1.67 (m, 1 H).
13C NMR (100 MHz, CDCl3): d = 136.7, 132.8, 131.4, 128.8, 128.1,
127.1, 75.0, 68.0, 32.9, 26.3.
HRMS (EI): m/z [M]+ calcd for C12H14O: 174.1045; found:
174.1053.
In conclusion, a promising protocol for the addition of sp3
2-[(E)-2-Phenylethenyl]tetrahydrofuran (Table 2, Entry 1)12a
1H NMR (400 MHz, CDCl3): d = 7.38 (d, J = 7.6 Hz, 2 H), 7.31 (t,
J = 7.4 Hz, 2 H), 7.22 (t, J = 7.4 Hz, 1 H), 6.58 (d, J = 15.6 Hz, 1
H), 6.21 (dd, J = 15.6, 6.8 Hz, 1 H), 4.48 (q, J = 7.2 Hz, 1 H), 3.98
(q, J = 7.2 Hz, 1 H), 3.85 (q, J = 7.3 Hz, 1 H), 2.17–2.10 (m, 1 H),
2.05–1.90 (m, 2 H), 1.76–1.67 (m, 1 H).
13C NMR (100 MHz, CDCl3): d = 136.7, 130.4, 130.3, 128.4, 127.4,
126.3, 79.5, 68.0, 32.3, 25.8.
HRMS (EI): m/z [M]+ calcd for C12H14O: 174.1045; found:
C–H bonds to alkynes has been established under mild
conditions in the presence, or absence, of metal catalysts.
The C–H bond adjacent to an oxygen atom in an alkyl
group is selectively cleaved to give the corresponding
alkyne adduct. The use of tert-butyl hydroperoxide as an
additive is crucial to the success of this coupling reaction.
Further studies on the mechanism and scope of this pro-
cess are currently in progress.
174.1037.
All reactions were carried out under a nitrogen atmosphere in oven-
dried flasks. THF was distilled over Na using benzophenone as the
indicator. Reagents and substrates were purchased from commer-
cial sources and were used without additional purification. 1H and
13C NMR spectra were recorded at 400 MHz or 500 MHz and 100
MHz or 125 MHz, respectively, using Bruker Avance DMX 400
and DMX 500 spectrometers, respectively, and TMS as the internal
standard. The NMR solvent is specified in each case. High resolu-
tion EI mass spectra were measured with a Micromass GCT-MS
spectrometer. Column chromatographic purification was carried
out on silica gel (300–400 mesh) purchased from Yinlong Compa-
ny.
2-[(Z)-2-(4-Methylphenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 2)12a
1H NMR (400 MHz, CDCl3): d = 7.21 (d, J = 8.0 Hz, 2 H), 7.15 (d,
J = 8.4 Hz, 2 H), 6.57 (d, J = 11.6 Hz, 1 H), 5.67 (dd, J = 11.6, 8.8
Hz, 1 H), 4.68 (q, J = 7.6 Hz, 1 H), 3.97 (q, J = 7.2 Hz, 1 H), 3.79
(dt, J = 7.8, 6.0 Hz, 1 H), 2.35 (s, 3 H), 2.18–2.11 (m, 1 H), 2.06–
1.88 (m, 2 H), 1.73–1.65 (m, 1 H).
13C NMR (100 MHz, CDCl3): d = 136.7, 133.7, 132.0, 131.3, 128.7,
128.6, 75.0, 67.9, 32.8, 26.2, 21.0.
HRMS (EI): m/z [M]+ calcd for C13H16O: 188.1201; found:
188.1193.
Copper-catalyzed Hydroalkylation of Alkynes; General Proce-
dure
2-[(E)-2-(4-Methylphenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 2)12a
To a mixture of alkyne (51 mg, 0.5 mmol), CuBr (7 mg, 0.05 mmol)
and THF (10 mL), tert-butyl hydroperoxide (0.10 mL, 5–6 M in de-
cane) was added dropwise under an N2 atm at r.t. The resulting mix-
ture was stirred at 50 °C for 12 h. On completion, the reaction
mixture was filtered through a pad of Celite and the solvent was re-
moved under reduced pressure. The residue was purified on a silica
gel column to afford the desired product.
1H NMR (400 MHz, CDCl3): d = 7.30 (d, J = 8.0 Hz, 2 H), 7.13 (d,
J = 8.0 Hz, 2 H), 6.58 (d, J = 16.0 Hz, 1 H), 6.18 (dd, J = 16.0, 6.8
Hz, 1 H), 4.48 (q, J = 6.7 Hz, 1 H), 3.99 (q, J = 7.3 Hz, 1 H), 3.86
(dt, J = 8.0, 6.0 Hz, 1 H), 2.35 (s, 3 H), 2.18–2.10 (m, 1 H), 2.06–
1.91 (m, 2 H), 1.77–1.69 (m, 1 H).
Synthesis 2009, No. 20, 3504–3510 © Thieme Stuttgart · New York

3508
L. Huang et al.
SPECIAL TOPIC
13C NMR (100 MHz, CDC l3): d = 137.1, 133.9, 130.3, 129.3,
129.0, 126.2, 79.7, 68.0, 32.2, 25.8, 21.0.
13C NMR (100 MHz, CDCl3): d = 150.1, 133.8, 132.3, 131.3, 128.6,
125.1, 75.1, 68.0, 34.5, 32.9, 31.3, 26.4.
HRMS (EI): m/z [M]+ calcd for C13H16O: 188.1201; found:
HRMS (EI): m/z [M]+ calcd for C16H22O: 230.1671; found:
188.1202.
230.1667.
2-[(Z)-2-(3-Methylphenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 3)
2-[(E)-2-(4-tert-Butylphenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 5)
1H NMR (400 MHz, CDCl3): d = 7.25 (t, J = 8.2 Hz, 1 H), 7.15–
7.09 (m, 3 H), 6.59 (d, J = 12.0 Hz, 1 H), 5.71 (dd, J = 12.0, 8.8 Hz,
1 H), 4.70 (q, J = 7.5 Hz, 1 H), 3.99 (q, J = 7.3 Hz, 1 H), 3.81 (dt,
J = 8.0, 6.0 Hz, 1 H), 2.38 (s, 3 H), 2.22–2.12 (m, 1 H), 2.08–1.90
(m, 2 H), 1.76–1.67 (m, 1 H).
1H NMR (400 MHz, CDCl3): d = 7.34 (s, 4 H), 6.58 (d, J = 16.0 Hz,
1 H), 6.18 (dd, J = 16.0, 6.8 Hz, 1 H), 4.48 (q, J = 6.8 Hz, 1 H), 3.98
(q, J = 7.5 Hz, 1 H), 3.85 (q, J = 7.3 Hz, 1 H), 2.17–2.09 (m, 1 H),
2.04–1.92 (m, 2 H), 1.76–1.69 (m, 1 H), 1.32 (s, 9 H).
13C NMR (100 MHz, CDCl3): d = 150.5, 134.1, 130.2, 129.7, 126.1,
125.4, 79.7, 68.1, 34.5, 32.4, 31.3, 25.9.
HRMS (EI): m/z [M]+ calcd for C16H22O: 230.1671; found:
230.1667.
13C NMR (100 MHz, CDCl3): d = 137.6, 136.6, 132.7, 131.5, 129.5,
128.0, 127.8, 125.8, 75.0, 68.0, 32.9, 26.3, 21.4.
HRMS (EI): m/z [M]+ calcd for C13H16O: 188.1201; found:
188.1198.
2-[(Z)-2-(4-Methoxyphenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 6)12a
2-[(E)-2-(3-Methylphenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 3)
1H NMR (400 MHz, CDCl3): d = 7.27 (d, J = 8.8 Hz, 2 H), 6.89 (d,
J = 8.4 Hz, 2 H), 6.55 (d, J = 11.2 Hz, 1 H), 5.64 (dd, J = 11.6, 8.8
Hz, 1 H), 4.68 (q, J = 7.7 Hz, 1 H), 3.98 (q, J = 7.3 Hz, 1 H), 3.83–
3.78 (m, 4 H), 2.20–2.12 (m, 1 H), 2.08–1.89 (m, 2 H), 1.74–1.65
(m, 1 H).
1H NMR (400 MHz, CDCl3): d = 7.23–7.18 (m, 3 H), 7.05 (d,
J = 7.6 Hz, 1 H), 6.56 (d, J = 16.0 Hz, 1 H), 6.20 (dd, J = 15.6, 6.8
Hz, 1 H), 4.47 (q, J = 6.8 Hz, 1 H), 3.98 (q, J = 7.5 Hz, 1 H), 3.85
(q, J = 7.3 Hz, 1 H), 2.34 (s, 3 H), 2.18–2.09 (m, 1 H), 2.05–1.89
(m, 2 H), 1.76–1.66 (m, 1 H).
13C NMR (100 MHz, CDCl3): d = 158.7, 131.2, 131.0, 130.0, 129.2,
113.5, 75.0, 67.9, 55.1, 32.8, 26.3.
HRMS (EI): m/z [M]+ calcd for C13H16O2: 204.1150; found:
204.1144.
13C NMR (100 MHz, CDCl3): d = 138.0, 136.7, 130.5, 130.3, 128.3,
128.2, 127.1, 123.6, 79.7, 68.1, 32.4, 25.9, 21.3.
HRMS (EI): m/z [M]+ calcd for C13H16O: 188.1201; found:
188.1194.
2-[(E)-2-(4-Methoxyphenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 6)12a
2-[(Z)-2-(4-Ethylphenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 4)
1H NMR (400 MHz, CDCl3): d = 7.33 (d, J = 8.8 Hz, 2 H), 6.86 (d,
J = 8.4 Hz, 2 H), 6.55 (d, J = 15.2 Hz, 1 H), 6.09 (dd, J = 16.0, 7.2
Hz, 1 H), 4.46 (q, J = 6.8 Hz, 1 H), 3.98 (q, J = 7.5 Hz, 1 H), 3.87–
3.82 (m, 4 H), 2.17–2.10 (m, 1 H), 2.06–1.90 (m, 2 H), 1.76–1.68
(m, 1 H).
1H NMR (500 MHz, CDCl3): d = 7.25 (d, J = 8.0 Hz, 2 H), 7.19 (d,
J = 8.0 Hz, 2 H), 6.59 (d, J = 12.0 Hz, 1 H), 5.69 (dd, J = 11.0, 8.5
Hz, 1 H), 4.71 (q, J = 7.7 Hz, 1 H), 3.98 (q, J = 7.3 Hz, 1 H), 3.81
(dt, J = 8.0, 6.0 Hz, 1 H), 2.67 (q, J = 7.8 Hz, 2 H), 2.19–2.13 (m, 1
H), 2.07–1.90 (m, 2 H), 1.74–1.67 (m, 1 H), 1.26 (t, J = 8.0 Hz, 3
H).
13C NMR (100 MHz, CDCl3): d = 159.0, 130.2, 129.5, 128.1, 127.5,
113.8, 79.8, 68.0, 55.1, 32.3, 25.8.
HRMS (EI): m/z [M]+ calcd for C13H16O2: 204.1150; found:
204.1144.
13C NMR (125 MHz, CDCl3): d = 143.5, 134.3, 132.4, 131.7, 129.1,
127.9, 75.4, 68.2, 33.1, 28.8, 26.6, 15.7.
HRMS (EI): m/z [M]+ calcd for C14H18O: 202.1358; found:
202.1353.
2-[(Z)-2-(4-Pentyloxyphenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 7)
2-[(E)-2-(4-Ethylphenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 4)
1H NMR (400 MHz, DMSO-d6): d = 7.21 (d, J = 8.4 Hz, 2 H), 6.89
(d, J = 8.4 Hz, 2 H), 6.44 (d, J = 11.6 Hz, 1 H), 5.54 (dd, J = 11.6,
8.8 Hz, 1 H), 4.52 (q, J = 7.6 Hz, 1 H), 3.93 (t, J = 6.6 Hz, 2 H), 3.80
(q, J = 7.2 Hz, 1 H), 3.63 (dt, J = 8.0, 6.4 Hz, 1 H), 2.15–2.07 (m, 1
H), 1.96–1.80 (m, 2 H), 1.69 (quin, J = 6.8 Hz, 2 H), 1.61–1.52 (m,
1 H), 1.40–1.27 (m, 4 H), 0.87 (t, J = 7.0 Hz, 3 H).
1H NMR (500 MHz, CDCl3): d = 7.32 (d, J = 8.0 Hz, 2 H), 7.15 (d,
J = 8.0 Hz, 2 H), 6.57 (d, J = 15.5 Hz, 1 H), 6.17 (dd, J = 15.5, 6.5
Hz, 1 H), 4.47 (q, J = 7.0 Hz, 1 H), 3.98 (q, J = 7.5 Hz, 1 H), 3.85
(dt, J = 8.0, 6.0 Hz, 1 H), 2.64 (q, J = 7.7 Hz, 2 H), 2.16–2.10 (m, 1
H), 2.04–1.91 (m, 2 H), 1.75–1.68 (m, 1 H), 1.24 (t, J = 7.8 Hz, 3
H).
13C NMR (100 MHz, DMSO-d6): d = 158.3, 131.8, 130.5, 130.3,
128.9, 114.6, 74.9, 67.7, 67.5, 32.8, 28.7, 28.1, 26.2, 22.3, 14.3.
HRMS (EI): m/z [M]+ calcd for C17H24O2: 260.1776; found:
260.1769.
13C NMR (125 MHz, CDCl3): d = 143.9, 134.6, 130.7, 129.8, 128.2,
126.7, 80.0, 68.4, 32.7, 28.8, 26.1, 15.8.
HRMS (EI): m/z [M]+ calcd for C14H18O: 202.1358; found:
202.1355.
2-[(E)-2-(4-Pentyloxyphenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 7)
2-[(Z)-2-(4-tert-Butylphenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 5)
1H NMR (400 MHz, CDCl3): d = 7.31 (d, J = 8.4 Hz, 2 H), 6.84 (d,
J = 8.8 Hz, 2 H), 6.53 (d, J = 15.6 Hz, 1 H), 6.07 (dd, J = 15.6, 6.4
Hz, 1 H), 4.45 (q, J = 7.1 Hz, 1 H), 4.00–3.93 (m, 3 H), 3.84 (dt,
J = 8.0, 6.4 Hz, 1 H), 2.16–2.08 (m, 1 H), 2.05–1.89 (m, 2 H), 1.79
(quin, J = 7.0 Hz, 2 H), 1.73–1.66 (m, 1 H), 1.48–1.34 (m, 4 H),
0.94 (t, J = 7.0 Hz, 3 H).
1H NMR (400 MHz, CDCl3): d = 7.39 (d, J = 8.4 Hz, 2 H), 7.27 (d,
J = 8.0 Hz, 2 H), 6.59 (d, J = 11.2 Hz, 1 H), 5.69 (dd, J = 12.0, 8.8
Hz, 1 H), 4.72 (q, J = 8.0 Hz, 1 H), 3.99 (q, J = 7.3 Hz, 1 H), 3.81
(dt, J = 8.0, 6.0 Hz, 1 H), 2.21–2.13 (m, 1 H), 2.08–1.90 (m, 2 H),
1.76–1.67 (m, 1 H), 1.35 (s, 9 H).
13C NMR (100 MHz, DMSO-d6): d = 158.7, 130.2, 129.4, 128.0,
127.6, 114.4, 79.9, 68.0, 67.9, 32.4, 28.9, 28.2, 26.0, 22.5, 14.0.
Synthesis 2009, No. 20, 3504–3510 © Thieme Stuttgart · New York

SPECIAL TOPIC
Copper-Catalyzed Hydroalkylation of Alkynes
3509
HRMS (EI): m/z [M]+ calcd for C17H24O2: 260.1776; found:
HRMS (EI): m/z [M]+ calcd for C11H13NO: 175.0997; found:
260.1769.
175.0999.
2-[(Z)-2-(4-Bromophenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 8)12a
2-[(Z)-2-Phenylethenyl]tetrahydrothiophene (Table 2, Entry
11)
1H NMR (500 MHz, CDCl3): d = 7.45 (d, J = 8.5 Hz, 2 H), 7.17 (d,
J = 8.5 Hz, 2 H), 6.51 (d, J = 11.5 Hz, 1 H), 5.73 (dd, J = 11.5, 8.5
Hz, 1 H), 4.59 (q, J = 7.7 Hz, 1 H), 3.95 (q, J = 7.3 Hz, 1 H), 3.78
(dt, J = 8.0, 6.5 Hz, 1 H), 2.15–2.09 (m, 1 H), 2.05–1.89 (m, 2 H),
1.71–1.64 (m, 1 H).
1H NMR (400 MHz, CDCl3): d 7.37–7.23 (m, 5 H), 6.44 (d, J = 11.2
Hz, 1 H), 5.68 (t, J = 10.8 Hz, 1 H), 4.38 (dt, J = 8.8, 6.0 Hz, 1 H),
3.07–3.01 (m, 1 H), 2.96–2.90 (m, 1 H), 2.25–2.15 (m, 2 H), 1.96–
1.85 (m, 1 H), 1.73–1.64 (m, 1 H).
13C NMR (100 MHz, CDCl3): d = 136.7, 133.5, 129.2, 128.7, 128.2,
126.9, 45.8, 38.7, 33.3, 31.1.
HRMS (EI): m/z [M]+ calcd for C12H14S: 190.0816; found:
190.0811.
13C NMR (100 MHz, CDCl3): d = 135.0, 133.1, 130.8, 129.9, 120.7,
74.3, 67.6, 32.4, 25.9.
HRMS (EI): m/z [M]+ calcd for C12H13BrO: 252.0150; found:
252.0144.
2-[(E)-2-Phenylethenyl]tetrahydrothiophene (Table 2, Entry
11)
2-[(E)-2-(4-Bromophenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 8)12a
1H NMR (400 MHz, CDCl3): d = 7.36 (d, J = 7.6 Hz, 2 H), 7.30 (t,
J = 7.4 Hz, 2 H), 7.21 (t, J = 7.4 Hz, 1 H), 6.46 (d, J = 16.0 Hz, 1
H), 6.17 (dd, J = 15.6, 8.8 Hz, 1 H), 4.12 (dt, J = 8.2, 6.0 Hz, 1 H),
3.05–2.99 (m, 1 H), 2.95–2.90 (m, 1 H), 2.26–2.15 (m, 2 H), 2.03–
1.92 (m, 1 H), 1.82–1.74 (m, 1 H).
1H NMR (400 MHz, CDCl3): d = 7.42 (d, J = 8.8 Hz, 2 H), 7.23 (d,
J = 8.4 Hz, 2 H), 6.52 (d, J = 16.0 Hz, 1 H), 6.20 (dd, J = 16.0, 6.4
Hz, 1 H), 4.45 (q, J = 6.8 Hz, 1 H), 3.96 (q, J = 7.3 Hz, 1 H), 3.84
(q, J = 7.3 Hz, 1 H), 2.17–2.09 (m, 1 H), 2.04–1.90 (m, 2 H), 1.74–
1.65 (m, 1 H).
13C NMR (100 MHz, CDCl3): d = 136.8, 131.6, 129.7, 128.4, 127.3,
126.2, 51.2, 38.2, 33.2, 30.9.
HRMS (EI): m/z [M]+ calcd for C12H14S: 190.0816; found:
190.0811.
13C NMR (100 MHz, CDCl3): d = 135.3, 131.1, 130.9, 128.7, 127.5,
120.7, 79.0, 67.7, 31.8, 25.4.
HRMS (EI): m/z [M]+ calcd for C12H13BrO: 252.0150; found:
252.0144.
2-[(Z)-2-Phenylethenyl]-1,3-dioxolane [(Z)-1a]14
2-[(Z)-2-(4-Fluorophenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 9)
1H NMR (400 MHz, CDCl3): d = 7.38–7.30 (m, 5 H), 6.84 (d,
J = 11.2 Hz, 1 H), 5.73 (dd, J = 12.0, 7.2 Hz, 1 H), 5.54 (d, J = 7.2
Hz, 1 H), 4.09 (t, J = 6.8 Hz, 2 H), 3.94 (t, J = 6.8 Hz, 2 H).
1H NMR (400 MHz, CDCl3): d = 7.24 (dd, J = 8.4, 5.6 Hz, 2 H),
6.99 (t, J = 8.4 Hz, 2 H), 6.51 (d, J = 11.6 Hz, 1 H), 5.66 (dd,
J = 11.6, 8.8 Hz, 1 H), 4.57 (q, J = 7.6 Hz, 1 H), 3.93 (q, J = 7.3 Hz,
1 H), 3.76 (dt, J = 8.0, 6.0 Hz, 1 H), 2.13–2.06 (m, 1 H), 2.03–1.85
(m, 2 H), 1.70–1.61 (m, 1 H).
13C NMR (100 MHz, CDCl3): d = 135.2, 128.5, 127.7, 127.3, 127.1,
126.1, 99.2, 64.7.
HRMS (EI): m/z [M]+ calcd for C11H12O2: 176.0837; found:
176.0835.
13C NMR (100 MHz, CDCl3): d = 161.8 (d, J = 244.9 Hz, 1 C),
132.5 (d, J = 4.3 Hz, 1 C), 130.4, 130.3, 130.2, 114.9 (d, J = 20.5
Hz, 1 C), 74.7, 67.9, 32.7, 26.2.
HRMS (EI): m/z [M]+ calcd for C12H13FO: 192.0950; found:
192.0945.
2-[(E)-2-Phenylethenyl]-1,3-dioxolane [(E)-1a]14
1H NMR (400 MHz, CDCl3): d = 7.43 (d, J = 7.6 Hz, 2 H), 7.34 (t,
J = 7.2 Hz, 2 H), 7.29 (t, J = 7.2 Hz, 1 H), 6.79 (d, J = 16.0 Hz, 1
H), 6.18 (dd, J = 16.0, 5.6 Hz, 1 H), 5.45 (d, J = 6.0 Hz, 1 H), 4.08
(t, J = 7.0 Hz, 2 H), 3.97 (t, J = 6.4 Hz, 2 H).
2-[(E)-2-(4-Fluorophenyl)ethenyl]tetrahydrofuran (Table 2,
Entry 9)13
13C NMR (100 MHz, CDCl3): d = 135.3, 134.4, 128.1, 127.9, 126.4,
124.6, 103.4, 64.6.
1H NMR (400 MHz, CDCl3): d = 7.30 (dd, J = 8.4, 5.6 Hz, 2 H),
6.96 (t, J = 8.6 Hz, 2 H), 6.51 (d, J = 16.0 Hz, 1 H), 6.09 (dd,
J = 16.0, 6.4 Hz, 1 H), 4.42 (q, J = 6.8 Hz, 1 H), 3.93 (q, J = 7.3 Hz,
1 H), 3.80 (q, J = 7.3 Hz, 1 H), 2.13–2.05 (m, 1 H), 2.01–1.86 (m, 2
H), 1.71–1.63 (m, 1 H).
HRMS (EI): m/z [M]+ calcd for C11H12O2: 176.0837; found:
176.0835.
2-[(Z)-2-(4-Methylphenyl)ethenyl]-1,3-dioxolane [(Z)-2a]14
1H NMR (400 MHz, CDCl3): d = 7.29 (d, J = 8.0 Hz, 2 H), 7.17 (d,
J = 7.6 Hz, 2 H), 6.80 (d, J = 11.6 Hz, 1 H), 5.69 (dd, J = 11.6, 7.6
Hz, 1 H), 5.55 (d, J = 7.2 Hz, 1 H), 4.08 (t, J = 6.8 Hz, 2 H), 3.98 (t,
J = 6.8 Hz, 2 H), 2.37 (s, 3 H).
13C NMR (100 MHz, CDCl3): d = 137.5, 135.5, 132.7, 128.8, 126.7,
125.0, 99.6, 65.0, 21.1.
13C NMR (100 MHz, CDCl3): d = 162.1 (d, J = 245.5 Hz, 1 C),
132.8 (d, J = 3.4 Hz, 1 C), 130.1 (d, J = 1.9 Hz, 1 C), 129.1, 127.8
(d, J = 7.6 Hz, 1 C), 115.2 (d, J = 21.6 Hz, 1 C), 79.4, 68.0, 32.2,
25.7.
HRMS (EI): m/z [M]+ calcd for C12H13FO: 192.0950; found:
192.0942.
HRMS (EI): m/z [M]+ calcd for C12H14O2: 190.0994; found:
190.0989.
2-[(E)-2-(Tetrahydrofuran-2-yl)ethenyl)pyridine (Table 2,
Entry 10)
2-[(E)-2-(4-Methylphenyl)ethenyl]-1,3-dioxolane [(E)-2a]14
1H NMR (400 MHz, CDCl3): d = 7.32 (d, J = 8.4 Hz, 2 H), 7.14 (d,
J = 7.6 Hz, 2 H), 6.76 (d, J = 16.4 Hz, 1 H), 6.13 (dd, J = 16.0, 6.0
Hz, 1 H), 5.43 (d, J = 6.4 Hz, 1 H), 4.07 (t, J = 6.4 Hz, 2 H), 3.96 (t,
J = 6.4 Hz, 2 H), 2.35 (s, 3 H).
13C NMR (100 MHz, CDCl3): d = 138.2, 134.8, 132.8, 129.1, 126.7,
123.8, 103.9, 64.9, 21.1.
1H NMR (400 MHz, CDCl3): d = 8.54 (d, J = 4.8 Hz, 1 H), 7.62 (dt,
J = 7.6, 2.0 Hz, 1 H), 7.28 (d, J = 7.6 Hz, 1 H), 7.12 (dd, J = 7.6, 5.6
Hz, 1 H), 6.74 (dd, J = 15.2, 5.6 Hz, 1 H), 6.67 (d, J = 15.6 Hz, 1
H), 4.57 (q, J = 6.4 Hz, 1 H), 3.98 (q, J = 7.2 Hz, 1 H), 3.86 (q,
J = 7.3 Hz, 1 H), 2.19–2.11 (m, 1 H), 2.04–1.89 (m, 2 H), 1.81–1.73
(m, 1 H).
13C NMR (100 MHz, CDCl3): d = 155.2, 149.3, 136.5, 135.3, 129.3,
122.0, 121.7, 78.9, 68.2, 32.1, 25.7.
Synthesis 2009, No. 20, 3504–3510 © Thieme Stuttgart · New York

3510
L. Huang et al.
SPECIAL TOPIC
HRMS (EI): m/z [M]+ calcd for C12H14O2: 190.0994; found:
190.0989.
Acknowledgment
Funding from the Natural Science Foundation of China (No.
205710631 and No. 20872126) and Zhejiang Provincial Natural
Science Foundation of China (R407106) is acknowledged.
2-[(Z)-2-(3-Methylphenyl)ethenyl]-1,3-dioxolane [(Z)-3a]
1H NMR (400 MHz, CDCl3): d = 7.25–7.17 (m, 3 H), 7.11 (d,
J = 7.2 Hz, 1 H), 6.80 (d, J = 11.6 Hz, 1 H), 5.70 (dd, J = 11.6, 7.2
Hz, 1 H), 5.53 (d, J = 7.6 Hz, 1 H), 4.07 (t, J = 6.8 Hz, 2 H), 3.92 (t,
J = 6.8 Hz, 2 H), 2.36 (s, 3 H).
References
13C NMR (100 MHz, CDCl3): d = 138.0, 135.6, 134.8, 129.0, 128.3,
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Chem. Int. Ed. 2005, 44, 6931. (e) Giri, R.; Chen, X.; Yu,
J.-Q. Angew. Chem. Int. Ed. 2005, 44, 2112. (f) Fleming,
J. J.; Fiori, K. W.; Bois, J. D. J. Am. Chem. Soc. 2003, 125,
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(4) Chatani, N.; Asaumi, T.; Yorimitsu, S.; Ikeda, T.; Kakiuchi,
F.; Murai, S. J. Am. Chem. Soc. 2001, 123, 10935.
(5) DeBoef, B.; Pastine, S. J.; Sames, D. J. Am. Chem. Soc.
2004, 126, 6556.
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C.-J. J. Am. Chem. Soc. 2005, 127, 3672. (c) Zhao, L.; Li,
C.-J. Angew. Chem. Int. Ed. 2008, 47, 7075. (d) Li, Z.; Yu,
R.; Li, H. Angew. Chem. Int. Ed. 2008, 47, 7497. (e)Zhang,
Y.; Fu, H.; Jiang, Y.; Zhao, Y. Org. Lett. 2007, 9, 3813.
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Chem. Soc. 2005, 127, 12180.
127.5, 124.7, 123.9, 103.8, 64.9, 21.2.
HRMS (EI): m/z [M]+ calcd for C12H14O2: 190.0994; found:
190.0988.
2-[(E)-2-(3-Methylphenyl)ethenyl]-1,3-dioxolane [(E)-3a]
1H NMR (400 MHz, CDCl3): d = 7.25–7.23 (m, 4 H), 6.76 (d,
J = 16.0 Hz, 1 H), 6.17 (dd, J = 16.0, 6.0 Hz, 1 H), 5.45 (d, J = 6.0
Hz, 1 H), 4.08 (t, J = 6.8 Hz, 2 H), 3.97 (t, J = 6.8 Hz, 2 H), 2.36 (s,
3 H).
13C NMR (100 MHz, CDCl3): d = 137.7, 135.7, 135.5, 129.5, 128.4,
128.0, 127.3, 125.9, 99.6, 65.0, 21.3.
HRMS (EI): m/z [M]+ calcd for C12H14O2: 190.0994; found:
190.0988.
2-[(Z)-2-(4-Ethylphenyl)ethenyl]-1,3-dioxolane [(Z)-4a]
1H NMR (400 MHz, CDCl3): d = 7.32 (d, J = 8.0 Hz, 2 H), 7.21 (d,
J = 8.0 Hz, 2 H), 6.82 (d, J = 11.6 Hz, 1 H), 5.70 (dd, J = 11.6, 7.2
Hz, 1 H), 5.56 (d, J = 7.6 Hz, 1 H), 4.09 (t, J = 6.8 Hz, 2 H), 3.94 (t,
J = 7.2 Hz, 2 H), 2.68 (q, J = 7.6 Hz, 2 H), 1.26 (t, J = 7.6 Hz, 3 H).
13C NMR (100 MHz, CDCl3): d = 144.5, 134.8, 133.1, 127.9, 126.8,
123.9, 103.9, 64.9, 28.5, 15.3.
HRMS (EI): m/z [M]+ calcd for C13H16O2: 204.1150; found:
204.1148.
2-[(E)-2-(4-Ethylphenyl)ethenyl]-1,3-dioxolane [(E)-4a]
1H NMR (400 MHz, CDCl3): d = 7.34 (d, J = 8.0 Hz, 2 H), 7.16 (d,
J = 8.0 Hz, 2 H), 6.75 (d, J = 15.6 Hz, 1 H), 6.12 (dd, J = 16.0, 6.0
Hz, 1 H), 5.42 (d, J = 6.4 Hz, 1 H), 4.06 (t, J = 6.8 Hz, 2 H), 3.95 (t,
J = 6.8 Hz, 2 H), 2.64 (q, J = 7.2 Hz, 2 H), 1.23 (t, J = 7.6 Hz, 3 H).
13C NMR (100 MHz, CDCl3): d = 143.8, 135.5, 133.0, 128.9, 127.6,
126.7, 99.7, 65.0, 28.5, 15.3.
HRMS (EI): m/z [M]+ calcd for C13H16O2: 204.1150; found:
204.1148.
2-[(Z)-2-(4-Bromophenyl)ethenyl]-1,3-dioxolane [(Z)-5a]
1H NMR (400 MHz, CDCl3): d 7.47 (d, J = 8.4 Hz, 2 H), 7.25 (d,
J = 8.0 Hz, 2 H), 6.73 (d, J = 12.0 Hz, 1 H), 5.75 (dd, J = 11.6, 7.2
Hz, 1 H), 5.45 (d, J = 7.2 Hz, 1 H), 4.07 (t, J = 7.2 Hz, 2 H), 3.92 (t,
J = 7.2 Hz, 2 H).
13C NMR (100 MHz, CDCl3): d = 134.1, 133.9, 130.9, 130.1, 128.0,
121.5, 99.0, 64.7.
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10, 5309. (b) Cheng, K.; Zhang, Y.; Zhao, J.; Xie, C. Synlett
2008, 1325.
(10) (a) Li, Z.; Li, C.-J. Org. Lett. 2004, 6, 4997. (b) Li, Z.; Li,
C.-J. J. Am. Chem. Soc. 2004, 126, 11810.
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Irie, M.; Fujiwara, Y. J. Am. Chem. Soc. 2000, 122, 7252.
(b) Reetz, M. T.; Sommer, K. Eur. J. Org. Chem. 2003,
3485.
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4300. (c) Zhang, Y.; Li, C.-J. J. Am. Chem. Soc. 2006, 128,
4242.
HRMS (EI): m/z [M]+ calcd for C11H11BrO2: 253.9942; found:
253.9944.
2-[(E)-2-(4-Bromophenyl)ethenyl]-1,3-dioxolane [(E)-5a]15
1H NMR (400 MHz, CDCl3): d = 7.32 (d, J = 8.0 Hz, 2 H), 7.14 (d,
J = 7.6 Hz, 2 H), 6.75 (d, J = 15.6 Hz, 1 H), 6.12 (dd, J = 16.0, 6.4
Hz, 1 H), 5.42 (d, J = 6.0 Hz, 1 H), 4.07 (t, J = 6.8 Hz, 2 H), 3.95 (t,
J = 6.8 Hz, 2 H).
13C NMR (100 MHz, CDCl3): d 134.5, 134.4, 131.3, 130.5, 128.4,
121.9, 99.4, 65.2.
(13) Jang, Y.-J.; Shih, Y.-K.; Liu, J.-Y.; Kuo, W.-Y.; Yao, C.-F.
Chem. Eur. J. 2003, 9, 2123.
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(15) Herm, M.; Fanghänel, E. DE102005036696, 2007; Chem.
Abstr. 2007, 146, 251600.
HRMS (EI): m/z [M]+ calcd for C11H11BrO2: 253.9942; found:
253.9944.
Synthesis 2009, No. 20, 3504–3510 © Thieme Stuttgart · New York