Regioselective Re(I)-catalyzed coupling of terminal alkynes, Et 2NH, and CO2 leading to anti-Markovnikov adducts

Article abstract of DOI:10.1016/j.tetlet.2005.11.137

ReBr(CO)₅-catalyzed addition of Et₂NH and CO ₂ to terminal alkynes afforded anti-Markovnikov adducts of alkenyl carbamates in good to excellent yield and high regioselectivity.

Full text of DOI:10.1016/j.tetlet.2005.11.137

Tetrahedron
Letters
Tetrahedron Letters 47 (2006) 953–955
Regioselective Re(I)-catalyzed coupling of terminal
alkynes, Et NH, and CO leading to anti-Markovnikov adducts
2
2
Jia-Li Jiang and Ruimao Hua*
Department of Chemistry, Tsinghua University, Innovative Catalysis Program, Key Laboratory of Organic
Optoelectronics and Molecular Engineering of Ministry of Education, Beijing 100084, China
Received 30 September 2005; revised 26 November 2005; accepted 29 November 2005
Available online 19 December 2005
5 2 2
Abstract—ReBr(CO) -catalyzed addition of Et NH and CO to terminal alkynes afforded anti-Markovnikov adducts of alkenyl car-
bamates in good to excellent yield and high regioselectivity.
Ó 2005 Elsevier Ltd. All rights reserved.
O
NEt2
Transition-metal-catalyzed transformation of carbon
ReBr(CO)5
R
R
+ CO2 + Et NH
2
dioxide into organic substrates is an important and chal-
O
1
ð2Þ
lenging research work in CO chemistry. Recently, we
2
anti-Markovnikov
Z- and E-adduct)
have reported that Re(I) complexes efficiently catalyze
(
the coupling of CO with epoxides to afford cyclic car-
2
2
bonates, and the addition of carboxylic acids (O–H
bond) to terminal alkynes giving alkenyl esters. These
3
Table 1 summarize the results of ReBr(CO) -catalyzed
5
reaction of terminal alkynes, Et NH, and CO . The
reactions were performed in a 25-mL autoclave using
.0 mmol of alkynes, 2.5 mmol of Et NH, and
5
,6
results indicate that Re(I) is an efficient catalyst in the
2
2
activation of CO and O–H bond of carboxylic acid.
2
2
2
0
.02 mmol of ReBr(CO) . CO (5.0 MPa) was pressur-
The synthesis of alkenyl carbamates through three-com-
ponents addition of terminal alkynes, secondary amines,
5
2
ized under atmosphere at ambient temperature. The
addition reaction of phenylacetylene in n-heptane at
110 °C for 24 h resulted in the formation of the anti-
Markovnikov addition product 2a in 82% GC yield with
a Z to E ratio of 89:11 (entry 1). In this case, only a trace
amount (<1%) of the Markovnikov addition product
was detectable by GC. In addition, the yield of 2a
and CO , catalyzed by ruthenium complexes has been
2
4
investigated in detail by DixneufÕs group and others.
However, in most cases, the addition reactions afforded
three adducts (Eq. 1), and both yield and selectivity re-
main yet to be improved. Therefore, the catalytic activ-
ity of ReBr(CO) has to be examined in the reaction of
5
depended on the pressure of CO . A low pressure of
CO2 led to a substantial decrease of yield (e.g.,
terminal alkynes with Et NH and CO . In this letter, we
2
2
2
report a ReBr(CO) -catalyzed three-component addi-
5
4.0 MPa, 55%; 2.0 MPa, 16%). Other aromatic alkynes
tion, which has given anti-Markovnikov adducts in
good to high yield (Eq. 2) regioselectively.
such as p-methylphenylacetylene and p-ethoxyphenyl-
acetylene showed similar reactivity as phenylacetylene,
which afforded the corresponding anti-Markovnikov
adducts 2b and 2c with a majority of Z-adduct (entries
O
cat. Ru
O
NR'2
+
R
R
+ CO2 + R' NH
2
R
O
NR'2
O ð1Þ
2
and 3).
Markovnikov
anti-Markovnikov
(
Z- and E-adduct)
Aliphatic alkynes also proceeded via such addition reac-
tions to give anti-Markovnikov addition products, but
in most cases with a significantly lower stereoselectivity
of Z-adduct. The addition of 1-octyne required a
prolonged reaction time to give the satisfactory yield
of adducts 2d, and the ratio of Z-2d and E-2d was
Keywords: Rhenium; Addition; Terminal alkyne; Amine; Carbamate.
Corresponding author. Tel./fax: +86 10 62792596; e-mail: ruimao@
mail.tsinghua.edu.cn
*
0040-4039/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2005.11.137

954
J.-L. Jiang, R. Hua / Tetrahedron Letters 47 (2006) 953–955
a
5 2 2
Table 1. Re(CO) Br-catalyzed three-component addition of alkyne, Et NH, and CO
ReBr(CO)5 (2.0 mol%)
solvent, 110 oC, 24 h
R
+ Et NH + scCO2
2
1
O
O
R
O
NEt2
+
O
NEt2
R
Solvent
Z - 2
E - 2
Yield of 2 (%)
b
c
Entry
R
Z:E
1
2
3
4
Ph
p-CH
n-Heptane
n-Heptane
n-Heptane
n-Heptane
n-Heptane
n-Heptane
Toluene
n-Heptane
n-Heptane
Toluene
2a
2b
2c
2d
2d
2e
2e
2f
82(71)
83(73)
90(82)
62
98(89)
54
84(53)
69(54)
57(50)
95(83)
89:11
85:15
86:14
52:48
52:48
60:40
62:38
58:42
95:5
3
C
6
H
4
p-C
n-C
n-C
NC(CH
NC(CH
Cl(CH
t-C
(CH
2
6
6
H
H
H
5
OC
6
H
4
13
13
d
5
6
7
8
9
2
)
)
3
3
2
2
)
3
4
H
)
9
2
2g
2h
10
3
C(OH)
85:15
a
Reactions were carried out at 110 °C for 24 h by using 2.0 mmol of 1, 3.0 mmol of Et
under the initial CO pressure of 5.0 MPa.
Determined by GC based on 1 used. Numbers in parentheses are isolated yield.
By GC of the reaction mixture.
For 35 h.
2
NH, and 0.04 mmol of Re(CO)
5
Br in a 25-mL autoclave
2
b
c
d
5
2:48 (entries 4 and 5). 5-Hexynenitrile occurred the
In summary, ReBr(CO) has shown to be an efficient
5
addition reaction in n-heptane to produce the adducts
e in 54% GC yield, while in toluene, the yield was in-
creased to 84% (entries 6 and 7). In n-heptane, the addi-
tion reactions of 5-chloro-1-pentyne and 3,3-dimethyl-1-
butyne afforded the anti-Markovnikov addition prod-
ucts 2f and 2g in 69% and 57% GC yields, respectively
transition-metal catalyst to catalyze the synthesis of
alkenyl carbamates via three-component addition of
Et NH and CO to terminal alkynes. The specific fea-
ture of present catalytic reaction is the high regioselec-
tivity giving the anti-Markovnikov adducts in good to
excellent yield.
2
2
2
(
(
entries 8 and 9). In the latter case, the high Z to E ratio
95:5) might owe to the existence of a bulky t-Bu group
in alkyne. Similarly, in the case of 3-hydroxy-3-methyl-
-butyne used, the addition reaction produced Z-adduct
Acknowledgments
1
in a good selectivity (entry 10).
This work was supported by National Natural Science
Foundation of China (20473043, 20573061).
It is noteworthy that under the same reaction condi-
tions, the addition reactions did not occur with internal
alkynes (e.g., 4-octyne, diphenyl acetylene). Internal
alkynes were recovered completely.
References and notes
1
2
. (a) Organic and Bio-organic Chemistry of Carbon Dioxide;
Inoue, S., Ed.; John Wiley & Sons, 1982; (b) Darensbourg,
D. J.; Holtcamp, M. W. Coord. Chem. Rev. 1996, 153, 155–
74; (c) Leitner, W. Coord. Chem. Rev. 1996, 153, 257–284;
d) Gibson, D. H. Chem. Rev. 1996, 96, 2063–2095.
. Jiang, J.-L.; Gao, F.; Hua, R.; Qiu, X. J. Org. Chem. 2005,
0, 381–383.
. Hua, R.; Tian, X. J. Org. Chem. 2004, 69, 5782–5784.
. (a) Sasaki, Y.; Dixneuf, P. H. J. Chem. Soc., Chem.
Commun. 1986, 790–791; (b) Mahe, R.; Dixneuf, P. H.;
Lecolier, S. Tetrahedron Lett. 1986, 27, 6333–6336; (c)
Bruneau, C.; Dixneuf, P. H. Tetrahedron Lett. 1987, 28,
In the ruthenium-catalyzed addition reactions of sec-
ondary amine and CO to terminal alkyne, the vinyl-
2
1
(
idene–ruthenium intermediate [Ru@C@CHR], which
was formed by the reaction of ruthenium complex with
terminal alkyne was postulated as the activated catalytic
7
7
3
species. On the basis of our previous work and the
known reaction behavior of carbon dioxide with second-
3
4
8
ary amine furnishing carbamic acid, we propose the
present catalytic formation of alkenyl carbamates
involving firstly the formation of carbamic acid, then a
subsequent addition of carbamic acid to alkynes as
shown in Scheme 1.
2
005–2008; (d) Mitsudo, T.; Hori, Y.; Yamakawa, Y.;
Watanabe, Y. Tetrahedron Lett. 1987, 28, 4417–4418; (e)
Mahe, R.; Sasaki, Y.; Bruneau, C.; Dixneuf, P. H. J. Org.
Chem. 1989, 54, 1518–1523; (f) Kayaki, Y.; Suzuki, T.;
Noguchi, Y.; Sakurai, S.; Imanari, M.; Ikariya, T. Chem.
Lett. 2002, 424–426.
ReBr(CO)5
O
NEt2
5. A typical experiment for the synthesis of Styryl N,N-
diethylcarbamate 2a (Table 1, entry 1): In a 25 mL stainless
steel autoclave equipped with a magnetic stirring bar,
Et NH
2
+
CO2
Et NCOOH
2
R
R
O
Scheme 1. Reaction pathway via carbamic acid.
phenyl acetylene 1a (2.0 mmol), Et NH (2.5 mmol),
2

J.-L. Jiang, R. Hua / Tetrahedron Letters 47 (2006) 953–955
955
ReBr(CO)
placed under air atmosphere. CO
.0 MPa at ambient temperature. The mixture was heated
5
(0.02 mmol), and n-heptane (1.0 mL) were
1H, J = 12.4, 6.5 Hz), other signals overlap with those of Z-
1
3
2
was then charged up to
isomer; C NMR (75.4 MHz, CDCl ) d 153.5, 136.7, 111.5;
3
+
5
GCMS m/z (% rel. inten.) 227(M , 2), 100(100), 72(41),
to 110 °C in oil bath, and stirred for 24 h. After cooling, the
gas was purged. The reaction mixture was diluted with
toluene to 2.0 mL and mesitylene (25.8 mg) was added as
internal standard. The analysis of the resulting mixture by
GC revealed that 2a (Z:E = 89:11) was formed in 85%
yield. After removal of the volatiles under vacuum, the
residue was purified by column chromatography (silica gel,
eluted with 5% diethyl ether/hexane) to afford 2a as
colorless as oil in 71%.
57(5), 44(15).
1
5-Cyano-1-pentenyl N,N-diethylcarbamate 2e: Z-2e:
NMR (300 MHz, CDCl
(dt, 1H, J = 7.0, 6.5 Hz), 3.32 (q, 4H, J = 7.2 Hz), 2.40–
H
3
) d 7.05 (d, 1H, J = 7.0 Hz), 4.66
2.24 (m, 4H), 1.76–1.70 (m, 2H), 1.15 (t, 6H, J = 7.2 Hz);
1
3
3
C NMR (75.4 MHz, CDCl ) d 152.9, 137.1, 119.5, 108.1,
42.1, 41.6, 25.0, 23.3, 16.4, 14.1, 13.3; GCMS m/z (% rel.
inten.) 210(M , 2), 82(3), 100(100), 72(74), 57(5), 44(40);
+
HRMS calcd for C11
H
18
N
2
O
2
210.1372, found 210.1368.
1
6
. All products 2 were isolated and gave satisfactory spectral
and/or analytical data as reported below.
E-2e: H NMR (300 MHz, CDCl ) d 7.04 (d, 1H,
3
J = 12.4 Hz), 5.20 (dt, 1H, J = 12.4, 6.5 Hz), 3.28 (q, 4H,
Styryl N,N-diethylcarbamate 2a (known compounds): Z-
J = 7.2 Hz), 2.32 (t, 2H, J = 7.2 Hz), 2.14 (td, 2H, J = 7.2,
1
13
2
a: H NMR (300 MHz, CDCl
3
) d 7.45 (d, 1H, J = 7.2 Hz),
6.5 Hz), 1.76–1.70 (m, 2H), 1.19 (t,6H, J = 7.2 Hz);
C
7
.28–7.20 (m, 5H), 5.53 (d, 1H, J = 7.2 Hz), 3.28 (q, 4H,
NMR (75.4 MHz, CDCl ) d 153.1, 138.2, 119.4, 109.4, 42.0,
3
1
3
J = 7.2 Hz), 1.11 (t, 6H, J = 7.2 Hz); C NMR (75.4 MHz,
CDCl ) d 152.7, 135.5, 128.5, 128.2, 126.7, 125.9, 109.4,
4
1
41.4, 26.2, 25.5, 16.3, 14.1, 13.3; GCMS m/z (% rel. inten.)
+
3
210(M , 2), 100(86), 72(69), 57(6), 44(40), 29(100).
3-Chloro-1-pentenyl N,N-diethylcarbamate 2f: Z-2f:
+
1
2.3, 41.7, 14.0, 13.2; GCMS m/z (% rel. inten.) 219(M ,
H
1
6), 147(1), 119(2), 100(100), 91(32), 77(7). E-2a: H NMR
NMR (300 MHz, CDCl ) d 7.01 (d, 1H, J = 6.8 Hz), 4.68
3
(
300 MHz, CDCl ) d 7.73 (d, 1H, J = 12.7 Hz), 7.20–7.10
(dt, 1H, J = 6.8, 6.5 Hz), 3.50 (t, 2H, J = 6.5 Hz), 3.30 (q,
3
(
m, 5H), 6.20 (d, 1H, J = 12.7 Hz), 3.33 (q, 4H, J = 7.2 Hz),
4H, J = 7.2 Hz), 2.27 (td, 2H, J = 7.2, 6.5 Hz), 1.85–1.80
(m, 2H), 1.12 (t, 6H, J = 7.2 Hz); C NMR (75.4 MHz,
1
3
13
1
1
1
1
2
.14 (t, 6H, J = 7.2 Hz); C NMR (75.4 MHz, CDCl
3
) d
53.2, 138.0, 134.6, 128.5, 128.2, 126.7, 112.5, 42.3, 41.7,
CDCl ) d 153.0, 136.5, 109.1, 44.4, 42.1, 41.6, 32.0, 21.7,
3
+
+
4.0, 13.2; GCMS m/z (% rel. inten.) 219(M , 15), 119(12),
14.1, 13.3; GCMS m/z (% rel. inten.) 219(M , 2), 100(68),
18(1.5), 100(100), 91(25), 77(5).
-p-Tolylvinyl N,N-diethylcarbamate 2b: Z-2b: H NMR
72(51); 57(8), 44(34), 29(100); HRMS calcd for
1
1
C
10
H18ClNO
2
219.1030, found 219.1026. E-2f: H NMR
(
300 MHz, CDCl ) d 7.35 (d, 2H, J = 7.9 Hz), 7.16 (d, 1H,
(300 MHz, CDCl ) d 7.03 (d, 1H, J = 12.4 Hz), 5.24 (dt,
3
3
J = 7.2 Hz), 7.05 (d, 2H, J = 7.9 Hz), 5.50 (d, 1H,
1H, J = 12.4, 6.5 Hz), 3.50 (t, 2H, J = 6.5 Hz), 3.30 (q, 4H,
J = 7.2 Hz), 3.29 (q, 4H, J = 7.2 Hz), 2.26 (s, 3H), 1.13 (t,
J = 7.2 Hz), 2.14 (td, 2H, J = 7.2, 6.5 Hz), 1.88–1.84 (m,
2H), 1.14 (t, 6H, J = 7.2 Hz); C NMR (75.4 MHz,
1
3
13
6
1
1
1
H, J = 7.2 Hz); C NMR (75.4 MHz, CDCl ) d 152.8,
3
34.9, 129.3, 128.9, 128.4, 125.8, 109.3, 42.2, 41.7, 21.1,
CDCl ) d 153.3, 137.7, 110.2, 44.1, 42.0, 41.4, 32.4, 24.5,
3
+
+
4.0, 13.3; GCMS m/z (% rel. inten.) 233(M , 7), 115(6),
14.1, 13.3; GCMS m/z (% rel. inten.) 219(M , 1), 100(44),
05(21), 100(100), 91(6), 79(9), 44(52); HRMS calcd for
72(37); 57(5), 44(23), 29(100).
3,3-Dimethyl-1-butenyl N,N-diethylcarbamate 2g, Z-2g: H
1
1
C H NO 233.1416, found 233.1416. E-2b: H NMR
1
4
19
2
(
300 MHz, CDCl
J = 12.7 Hz), 3.33 (q, 4H, J = 7.2 Hz), 2.24 (s, 3H), 1.14 (t,
H, J = 7.2 Hz), signals of aromatic ring overlap with those
3
) d 7.86 (d, 1H, J = 12.7 Hz), 6.19 (d, 1H,
NMR (300 MHz, CDCl
(d, 1H, J = 7.2 Hz), 3.27 (q, 4H, J = 7.2 Hz), 1.10 (t, 6H,
J = 7.2 Hz), 1.08 (s, 9H); C NMR (75.4 MHz, CDCl ) d
3
153.2, 133.2, 120.3, 42.0, 41.4, 31.5, 30.5(3C), 14.1, 13.3;
3
) d 6.77 (d, 1H, J = 7.2 Hz), 4.54
1
3
6
+
of Z-isomer; GCMS m/z (% rel. inten.) 233(M , 10), 115(6),
1
+
05(20), 100(100), 91(5), 79(6), 77(13), 44(26).
GCMS m/z (% rel. inten.) 199(M , 2), 100(85), 83(6);
2
-(4-Ethoxyphenyl)vinyl N,N-diethylcarbamate 2c: Z-2c:
72(57); 57(4), 44(33), 29(100); HRMS calcd for C11
199.1572, found 199.1572.
H21NO
2
1
H NMR (300 MHz, CDCl
3
) d 7.45 (d, 2H, J = 8.7 Hz),
.18 (d, 1H, J = 7.2 Hz), 6.84 (d, 2H, J = 8.7 Hz), 5.54 (d,
H, J = 7.2 Hz), 4.02 (q, 2H, J = 6.9 Hz), 3.37 (q, 4H,
7
1
3-Hydroxy-3-methyl-1-butenyl N,N-diethylcarbamate 2h,
1
Z-2h: H NMR (300 MHz, CDCl
3
) d 6.88 (d, 1H, J =
J = 7.2 Hz), 1 1.40 (t, 3H, J = 6.9 Hz), 1.18 (t, 6H,
7.2 Hz), 4.84 (d, 1H, J = 7.2 Hz), 3.26 (q, 4H, J = 7.2 Hz),
3
13
J = 7.2 Hz); C NMR (75.4 MHz, CDCl ) d 157.6, 152.8,
1.86 (s, 1H), 1.37 (s, 6H), 1.09 (t, 6H, J = 7.2 Hz);
C
3
1
1
1
33.9, 129.7, 127.1, 114.1, 109.0, 63.3, 42.2, 41.6, 14.8, 14.0,
3.2; GCMS m/z (% rel. inten.) 263(M , 33), 107(49),
NMR (75.4 MHz, CDCl ) d 153.3, 133.8, 118.2, 70.0, 42.2,
3
+
41.5, 30.3(2C), 14.1, 13.2; GCMS m/z (% rel. inten.)
+
01(16), 100(100), 91(7), 77(20); HRMS calcd for
201(M , 0.5), 158(22), 116(13), 100(100), 85(3), 72(61),
1
C H NO 263.1520, found 263.1521. E-2c: H NMR
57(15), 44(22); HRMS calcd for C H NO 201.1364,
1
5
21
3
10 19
3
1
(
300 MHz, CDCl
3
) d 7.69 (d, 1H, J = 12.7 Hz), 6.25 (d, 1H,
3
found 201.1365. E-2h: H NMR (300 MHz, CDCl ) d 7.19
J = 12.7 Hz), 4.02 (q, 2H, J = 6.9 Hz), 3.42 (q, 4H,
(d, 1H, J = 12.7 Hz), 5.45 (d, 1H, J = 12.7 Hz), 3.24 (q, 4H,
J = 7.2 Hz), 1.40 (t, 3H, J = 6.9 Hz), 1.23 (t, 6H, J =
J = 7.2 Hz), 2.27 (s, 1H), 1.30 (s, 6H), 1.07 (t, 6H,
J = 7.2 Hz); GCMS m/z (% rel. inten.) 201(M , 0.5),
100(100), 72(72), 57(15), 44(23).
+
7
.2 Hz), signals of aromatic ring overlap with those of
+
Z-isomer; GCMS m/z (% rel. inten.) 263(M , 13), 107(27),
1
1
01(6), 100(100), 91(4), 77(11).
-Octenyl N,N-diethylcarbamate 2d: Z-2d:
7. Dixneuf, P. H.; Bruneau, C.; Derien, S. Pure Appl. Chem.
1998, 70, 1055–1070.
1
H NMR
(
300 MHz, CDCl ) d 6.91 (d, 1H, J = 7.5 Hz), 4.67 (dt,
8. The formation of N,N-dialkylcarbamic acid by the reaction
3
1
H, J = 7.5, 6.5 Hz), other signals overlap with those of
2
of secondary amine with CO has been reported, see: (a)
1
3
E-isomer; C NMR (75.4 MHz, CDCl
1
mixtureÕs C NMR data; GCMS m/z (% rel. inten.)
2
3
) d 153.6, 135.3,
Furstner, A.; Ackermann, L.; Beck, K.; Hori, H.; Koch, D.;
Langemann, K.; Liebl, M.; Six, C.; Leitner, W. J. Am.
Chem. Soc. 2001, 123, 9000–9006; (b) Wittmann, K.;
Wisniewski, W.; Mynott, R.; Leitner, W.; Kranemann, C.
L.; Rische, T.; Eilbracht, P.; Kluwer, S.; Ernsting, J. M.;
Elsevier, C. J. Chem. Eur. J. 2001, 7, 4584–4589.
12.5, other signals can not be assigned from the Z/E
1
3
+
27(M , 2), 100(100), 72(43), 57(6), 44(15); HRMS calcd
1
for C13
2
H25NO 227.1889, found 227.1885. E-2d: H NMR
(
300 MHz, CDCl ) d 6.94 (d, 1H, J = 12.4 Hz), 5.23 (dt,
3