Cobalt-catalyzed addition of styrylboronic acids to 2-vinylpyridine derivatives

Article abstract of DOI:10.1002/asia.201000275

Treatment of 2-vinyl nitrogen-containing heteroaromatic compounds with styrylboronic acid in the presence of a cobalt catalyst and a base results in an addition reaction to afford the corresponding 4-phenyl-3-butenyl heteroarenes. The adjacent nitrogen atom is essential for the promotion of the reaction because the nitrogen accelerates the addition of the styryl cobalt species, generated by transmetalation, onto the vinyl group. The reaction represents a rare example of cobalt catalysis in the reactions of organoboronic acids. Accelerated addition: Treatment of 2-vinylpyridine derivatives with styrylboronic acids under cobalt catalysis results in addition reactions. This represents a rare example of the cobalt-catalyzed reaction of organoboronic acids. Cobalt shows catalytic activity similar to rhodium, and catalyzes an unprecedented assembly of organoboronic acids and activated alkenes. Copyright

Full text of DOI:10.1002/asia.201000275

DOI: 10.1002/asia.201000275
Cobalt-Catalyzed Addition of Styrylboronic Acids to 2-Vinylpyridine
Derivatives
Tsuneyuki Kobayashi, Hideki Yorimitsu,* and Koichiro Oshima*[a]
Dedicated to Professor Eiichi Nakamura on the occasion of his 60th birthday
Abstract: Treatment of 2-vinyl nitrogen-containing heteroaromatic compounds
with styrylboronic acid in the presence of a cobalt catalyst and a base results in an
addition reaction to afford the corresponding 4-phenyl-3-butenyl heteroarenes.
The adjacent nitrogen atom is essential for the promotion of the reaction because
the nitrogen accelerates the addition of the styryl cobalt species, generated by
transmetalation, onto the vinyl group. The reaction represents a rare example of
cobalt catalysis in the reactions of organoboronic acids.
Keywords: addition reactions
alkenylation · cobalt · heterocycles ·
organoborons
·
Introduction
transition metal that can catalyze addition to vinyl heteroar-
enes. We are interested in the catalytic activity of cobalt in
organic synthesis,[6–8] and report herein the cobalt-catalyzed
addition of alkenylboronic acids to vinyl heteroarenes. The
present reaction represents a rare example of cobalt cataly-
sis in the addition reactions of organoboron reagents. To the
best of our knowledge, cobalt-catalyzed addition of arylbor-
onic acids to activated alkynes is the only precedent for the
combined use of organoboronic acids and a cobalt catalyst.[9]
The transition metal catalyzed addition of organometallic
reagents to activated alkenes is a useful carbon carbon
À
bond forming reaction in organic synthesis.[1] Organoboron
reagents have been attracting increasing attention, owing to
their easy handling, low toxicity, and widespread availability.
Rhodium catalysis is now recognized as the most reliable
method for 1,4-addition to a,b-unsaturated carbonyl com-
pounds.[2] However, examples of addition onto alkenes acti-
vated by a heteroaromatic ring are limited.
Lautens and co-workers,[3,4] and Michelet, GenÞt, and co-
workers[5] have reported the rhodium-catalyzed addition of
arylboronic acids to vinylpyridine derivatives in water. In
these reports, there are no examples of the use of alkenyl-
boronic acids. It is also noteworthy that rhodium is the only
Results and Discussion
The reaction of 2-vinylpyridine (1a) with styrylboronic acid
(2a, 3 equiv) proceeded very efficiently in the presence of
potassium carbonate (2 equiv), cobalt(II) bromide
(5 mol%), and triphenylphosphine (10 mol%) (Table 1,
entry 1). The use of the excess of 2a is important. The use
of 2 equiv of 2a gave 3a in slightly lower (yet still high)
yield (entry 2). A significant drop in yield was observed
when 1 equiv of 2a was employed (entry 3). In this case, all
of the 2a disappeared, and a large amount of styrene and a
small amount of 1,4-diphenyl-1,3-butadiene were detected.
Protonation of 2a and the styryl cobalt species generated by
transmetalation (see below) must compete to consume 2a.
In the absence of base, the yield of 2a was moderate
(entry 4). While other potassium salts such as phosphate and
hydroxide were also effective, sodium carbonate and cesium
carbonate were inferior (entries 5–8). Interestingly, cesium
fluoride was as effective as potassium bases (entry 9). The
[a] T. Kobayashi, Prof. Dr. H. Yorimitsu,+ Prof. Dr. K. Oshima
Department of Material Chemistry
Graduate School of Engineering
Kyoto University
Kyoto-daigaku Katsura, Nishikyo, Kyoto 615-8510 (Japan)
E-mail: oshima@orgrxn.mbox.media.kyoto-u.ac.jp
[+] Present Address:
Department of Chemistry
Graduate School of Science
Kyoto University
Kitashirakawa, Sakyo, Kyoto 606-8502 (Japan)
Fax : (+81)75-753-3970
E-mail: yori@kuchem.kyoto-u.ac.jp
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201000275.
Chem. Asian J. 2011, 6, 669 – 673
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
669

FULL PAPERS
Table 1. Effects of amount of 2a, base, and solvent.
Table 2. Scope of vinyl heteroaromatic substrates.
Entry
1
1
Product
Yield [%]
78
Entry
1
Deviation from standard conditions
3a [%]
3b
none
amount of 2a
2 equiv 2a
1 equiv 2a
base
no base
K3PO4
KOH
Na2CO3
96
2
3
3c
3d
45
58
2
3
91
44
4
5
6
7
8
9
38
88
71
38
33
87
4
5
6
3e
3 f
3g
76
0
Cs2CO3
CsF
solvent
0
10
11
12
13
xylene, reflux
dioxane, reflux
acetonitrile, reflux
DMF, reflux
75
64
0
7
8
3h
3i
0
0
78
exact role of the base remains unclear. While a reaction in
xylene or dioxane did proceed, more polar solvents, such as
acetonitrile and dimethyl formamide, completely suppressed
the reactions (entries 10–13). These highly polar solvents
must strongly coordinate to cobalt and interrupt the coordi-
nation of the nitrogen atom of 1a (see below).
9
3j
85
10
11
3k
3l
71
0
The scope of vinyl heteroarenes in these reactions is sum-
marized in Table 2. The reactions of 2-vinylpyridine analogs
such as 2-vinylpyrimidine (1b) and -pyrazine (1c) proceeded
smoothly (entries 1–4). In contrast, 2-vinylthiophene (1 f), 3-
vinylpyridine (1g), and 4-vinylpyridine (1h) resisted the re-
action (entries 5–7). 2-Vinylpyridine derivatives bearing a
methyl group at the 3-, 4-, or 5-position underwent the addi-
tion reaction (entries 8–10). Interestingly, 6-methyl-2-vinyl-
pyridine failed to react (entry 11). The nitrogen atom in the
heteroaromatic ring clearly plays a key role in the addition
reaction, probably coordinating to the cobalt, which then ac-
celerates the addition reaction (see below). The correspond-
ing 2-vinylpyridine N-oxides were too unstable to use as
substrates, because they underwent polymerization.
of the internal double bond (see Scheme 1). While (Z)-1m
remained intact under the standard conditions, the reaction
of the E isomer proceeded smoothly.
Scheme 1. Stereochemical control of the addition to 1m.
It is worth noting that the efficiency of the addition to 2-
(1-propenyl)pyridine (1m) depended on the stereochemistry
An electron-neutral or -donating substituent at the para
position of styrylboronic acids had little influence on the ef-
ficiency of the reaction (Table 3, entries 1, 3, and 5). In con-
trast, the ortho substituent of 2c and the para electron-with-
drawing group of 2e diminished the yields of the corre-
sponding adducts (entries 2 and 4), probably because of
slower transmetalation (see below). 2-(2-Thienyl)ethenylbor-
onic acid (2g) participated in the addition reaction (entry 6).
Unfortunately, 1-phenylethenylboronic acid, phenylboronic
acids, and 1-hexenylboronic acid failed to react. In these
cases, small amounts of homocoupling products, such as 2,3-
diphenyl-1,3-butadiene, biphenyl, and 5,7-dodecadiene were
observed, which indicates that transmetalation from boron
Abstract in Japanese:
670
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ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2011, 6, 669 – 673

Cobalt-Catalyzed Addition of Styrylboronic Acids
Table 3. Scope of organoboronic acids.
accelerate the regioselective insertion of 1a to yield 6. Pro-
tonation of 6 with 2a or other possible proton sources, such
as potassium hydrogen carbonate, would afford product 3a
and regenerate 4.
Entry
1
2
Product
Yield [%]
86
Conclusions
3n
We have developed a cobalt-catalyzed addition of alkenyl-
boronic acids to vinyl heteroarenes. Cobalt is cheaper and
more abundant than rhodium. In this report, cobalt proves
to show similar catalytic activity to rhodium, and to catalyze
the unprecedented assembly of organoboronic acids and ac-
tivated alkenes.
2
3
4
3o
3p
3q
41
75
39
Experimental Section
Typical Procedure
The reaction of 2-vinylpyridine (1a) with styrylboronic acid (2a) is repre-
sentative (Table 1, entry 1). Cobalt(II) bromide (5.5 mg, 0.025 mmol), tri-
phenylphosphine (13.1 mg, 0.050 mmol), potassium carbonate (138 mg,
1.0 mmol), and 2a (222 mg, 1.5 mmol) were placed in a 20 mL reaction
5
6
3r
3s
72
63
flask under argon. Toluene (2.0 mL) was added.
A solution of 1a
(52.6 mg, 0.50 mmol) in toluene (1.5 mL) was then added at room tem-
perature. The mixture was stirred for 4 h at reflux. Water (10 mL) was
added, and the organic compounds were extracted with ethyl acetate
(10 mLꢁ3). The combined organic phase was dried over anhydrous
sodium sulfate and concentrated. Silica gel column purification afforded
1-phenyl-4-(2-pyridyl)-1-butene (3a, 101 mg, 0.48 mmol, 96%).
to cobalt proceeded, but that the subsequent addition to 1a
was sluggish.
It is possible that the reaction mechanism is similar to
that of the well-known rhodium-catalyzed reaction
(Scheme 2). Initially, a divalent cobalt species would be re-
duced in situ to monovalent cobalt 4 since the reaction of
Characterization Data for New Products
1-Phenyl-4-(2-pyridyl)-1-butene (3a): IR (neat): n˜ =2924, 2855, 1588,
1
1458, 1373, 964 cmÀ1; H NMR (CDCl3): d=2.66 (dt, J=7.5, 7.5 Hz, 2H),
2.96 (t, J=7.5 Hz, 2H), 6.26 (dt, J=16.0, 7.5 Hz, 1H), 6.42 (d, J=
16.0 Hz, 1H), 7.11 (dd, J=5.0, 7.5 Hz, 1H), 7.14–7.21 (m, 2H), 7.25–7.34
(m, 4H), 7.58 (dt, J=7.5, 2.0 Hz, 1H), 8.55 ppm (d, J=5.0 Hz, 1H);
13C NMR (CDCl3): d=33.21, 38.28, 121.25, 123.02, 126.14, 127.08, 128.60,
129.81, 130.70, 136.43, 137.80, 149.48, 161.44 ppm; elemental analysis:
calcd (%) for C15H15N: C 86.08, H 7.22; found: C 86.16, H 7.29.
1a with 2a proceeded in the presence of CoClACHTNUTRGNE(UNG PPh3)3 (80%
yield).[10] The monovalent cobalt 4 would then undergo
transmetalation with the aid of potassium carbonate to yield
styryl cobalt 5. The coordinating proximal nitrogen would
1-Phenyl-4-(2-pyrimidyl)-1-butene (3b): m.p.: 40–448C. IR (nujol): n˜ =
1
2924, 2855, 2361, 1558, 1458 cmÀ1; H NMR (CDCl3): d=2.77 (dt, J=7.0,
7.0 Hz, 2H), 3.15 (t, J=7.0 Hz, 2H), 6.30 (dt, J=16.0, 7.0 Hz, 1H), 6.44
(d, J=16.0 Hz, 1H), 7.12 (dd, J=5.0, 5.0 Hz, 1H), 7.18 (dd, J=7.5,
7.5 Hz, 1H), 7.23 (dd, J=7.5, 7.5 Hz, 2H), 7.32 (d, J=7.5 Hz, 2H),
8.68 ppm (d, J=5.0 Hz, 2H); 13C NMR (CDCl3): d=31.93, 39.35, 118.71,
126.20, 127.11, 128.61, 129.60, 130.77, 137.80, 157.19, 170.82 ppm; HRMS
(DI-EI+) (m/z) observed: 210.1158 (D=+0.7 ppm); calcd for C14H14N2
[M+]: 210.1157.
1-Phenyl-4-(2-pyrazyl)-1-butene (3c): IR (neat): n˜ =2924, 2855, 2361,
1
1458, 1373 cmÀ1; H NMR (CDCl3): d=2.68 (dt, J=7.0, 7.5 Hz, 2H), 3.00
(t, J=7.5 Hz, 2H), 6.24 (dt, J=16.0, 7.0 Hz, 1H), 6.42 (d, J=16.0 Hz,
1H), 7.20 (dd, J=2.0, 2.0 Hz, 1H), 7.25–7.35 (m, 4H), 8.41 (d, J=2.5 Hz,
1H), 8.48 (s, 1H), 8.52 ppm (d, J=2.5 Hz, 1H); 13C NMR (CDCl3): d=
32.64, 35.41, 126.21, 127.31, 128.67, 128.93, 131.31, 137.55, 142.50, 144.30,
144.83, 157.04 ppm; elemental analysis: calcd (%) for C14H14N2: C 79.97,
H 6.71; found: C 79.82, H 6.75.
1-Phenyl-4-(2-quinolyl)-1-butene (3d): IR (neat): n˜ =2924, 2855, 2731,
1458, 1373, 1034 cmÀ1 1H NMR (CDCl3): d=2.76 (dt, J=6.5, 7.5 Hz,
;
2H), 3.16 (t, J=7.5 Hz, 2H), 6.32 (dt, J=16.0, 6.5 Hz, 1H), 6.45 (d, J=
16.0 Hz, 1H), 7.19 (dd, J=7.0, 7.0 Hz, 1H), 7.26–7.34 (m, 5H), 7.49 (dd,
J=8.0, 8.0 Hz, 1H), 7.69 (dd, J=8.0, 8.0 Hz, 1H), 7.78 (d, J=8.0 Hz,
1H), 8.06 (d, J=8.0 Hz, 1H), 8.07 ppm (d, J=8.0 Hz, 1H); 13C NMR
(CDCl3): d=33.31, 39.20, 121.66, 125.97, 126.23, 127.01, 127.17, 127.71,
Scheme 2. A plausible mechanism.
Chem. Asian J. 2011, 6, 669 – 673
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671

H. Yorimitsu, K. Oshima, and T. Kobayashi
FULL PAPERS
128.66, 129.12, 129.59, 129.83, 130.87, 136.44, 137.86, 148.24, 162.06 ppm;
elemental analysis: calcd (%) for C19H17N: C 87.99, H 6.61; found:
C 88.07, H 6.83.
6.12 (dt, J=15.5, 7.0 Hz, 1H), 6.36 (d, J=15.5 Hz, 1H), 6.83 (d, J=
9.0 Hz, 2H), 7.11 (dd, J=5.0, 7.5 Hz, 1H), 7.16 (d, J=7.5 Hz, 1H), 7.26
(d, J=9.0 Hz, 2H), 7.58 (dd, J=7.5, 7.5 Hz, 1H), 8.55 ppm (d, J=5.0 Hz,
1H); 13C NMR (CDCl3): d=33.25, 38.50, 55.45, 114.07, 121.24, 123.04,
127.25, 127.68, 130.07, 130.69, 136.42, 149.51, 158.92, 161.61 ppm; HRMS
(DI-EI+) (m/z) observed:239.1315 (D=+2.2 ppm); calcd for C16H17NO
[M+]: 239.1310.
1-Phenyl-4-(2-thiazolyl)-1-butene (3e): IR (neat): n˜ =3024, 2847, 1705,
1497, 964, 741 cmÀ1 1H NMR (CDCl3): d=2.73 (dt, J=7.0, 7.0 Hz, 2H),
;
3.21 (t, J=7.0 Hz, 2H), 6.26 (dt, J=16.0, 7.0 Hz, 1H), 6.46 (d, J=
16.0 Hz, 1H), 7.19 (d, J=3.0 Hz, 1H), 7.20–7.22 (m, 1H), 7.27–7.35 (m,
4H), 7.70 ppm (d, J=3.0 Hz, 1H); 13C NMR (CDCl3): d=33.27, 33.29,
118.36, 126.26, 127.35, 128.53, 128.68, 131.59, 137.54, 142.47, 170.33 ppm;
elemental analysis: calcd (%) for C13H13NS: C 72.52, H 6.09; found:
C 72.73, H 6.13.
4-(2-Pyridyl)-1-(4-trifluoromethylphenyl)-1-butene (3q): m.p.: 66–698C.
IR (nujol): n˜ =2855, 2677, 2361, 1458, 1373, 1126 cmÀ1
;
1H NMR
(CDCl3): d=2.70 (dt, J=6.5, 7.5 Hz, 2H), 2.98 (t, J=7.5 Hz, 2H), 6.37
(dt, J=16.0, 6.5 Hz, 1H), 6.45 (d, J=16.0 Hz, 1H), 7.13 (dd, J=5.0,
7.5 Hz, 1H), 7.17 (d, J=7.5 Hz, 1H), 7.40 (d, J=8.0 Hz, 2H), 7.53 (d, J=
8.0 Hz, 2H), 7.60 (dd, J=7.5, 7.5 Hz, 1H), 8.56 ppm (d, J=5.0 Hz, 1H);
13C NMR (CDCl3): d=33.17, 38.02, 121.38, 123.03, 123.37, 125.58 (q, J=
31.0 Hz), 126.29, 128.95 (q, J=257 Hz), 129.57, 132.73, 136.51, 141.31,
149.58, 161.18 ppm; HRMS (DI-EI+) (m/z) observed: 277.1074 (D=
À1.7 ppm); calcd for C16H14F3N [M+]: 277.1078.
1-Phenyl-4-(3-methyl-2-pyridyl)-1-butene (3i): IR (neat): n˜ =3024, 2932,
1582, 1450, 965, 741 cmÀ1 1H NMR (CDCl3): d=2.33 (s, 3H), 2.65 (dt,
;
J=7.0. 8.0 Hz, 2H), 2.95 (t, J=8.0 Hz, 2H), 6.32 (dt, J=16.0, 7.0 Hz,
1H), 6.44 (d, J=16.0 Hz, 1H), 7.04 (dd, J=5.0, 7.5 Hz, 1H), 7.19 (dd, J=
7.0, 7.0 Hz, 1H), 7.26–7.35 (m, 4H), 7.41 (d, J=7.5 Hz, 1H), 8.40 ppm (d,
J=5.0 Hz, 1H); 13C NMR (CDCl3): d=19.02, 32.25, 35.39, 121.39, 126.18,
127.09, 128.65, 130.25, 130.51, 131.15, 137.73, 137.92, 146.95, 159.74 ppm;
elemental analysis: calcd (%) for C16H17N: C 86.05, H 7.67; found:
C 85.80, H 7.74.
1-(4-Chlorophenyl)-4-(2-pyridyl)-1-butene (3r): m.p.: 51–528C. IR
(nujol): n˜ =2924, 2855, 2700, 1458, 1373, 1304, 964 cmÀ1
;
1H NMR
(CDCl3): d=2.66 (dt, J=7.0, 8.0 Hz, 2H), 2.96 (t, J=8.0 Hz, 2H), 6.24
(dt, J=16.0, 7.0 Hz, 1H), 6.37 (d, J=16.0 Hz, 1H), 7.12 (dd, J=4.5,
8.0 Hz, 1H), 7.16 (d, J=8.0 Hz, 1H), 7.24 (s, 4H), 7.60 (dd, J=8.0,
8.0 Hz, 1H), 8.55 ppm (d, J=4.5 Hz, 1H); 13C NMR (CDCl3): d=33.18,
38.21, 121.35, 123.05, 127.39, 128.77, 129.59, 130.62, 132.69, 136.35, 136.49,
149.57, 161.35 ppm; elemental analysis: calcd (%) for C15H14ClN:
C 73.92, H 5.79; found: C 73.88, H 5.82.
1-Phenyl-4-(4-methyl-2-pyridyl)-1-butene (3j): IR (neat): n˜ =3024, 2924,
1605, 1443, 964, 741 cmÀ1 1H NMR (CDCl3): d=2.32 (s, 3H), 2.65 (dt,
;
J=6.5, 7.5 Hz, 2H), 2.92 (t, J=7.5 Hz, 2H), 6.27 (dt, J=16.0, 6.5 Hz,
1H), 6.43 (d, J=16.0 Hz, 1H), 6.94 (d, J=5.0 Hz, 1H), 7.00 (s, 1H),
7.17–7.21 (m, 1H), 7.25–7.34 (m, 4H), 8.40 ppm (d, J=5.0 Hz, 1H);
13C NMR (CDCl3): d=21.18, 33.31, 38.19, 122.34, 123.95, 126.18, 127.10,
128.64, 130.02, 130.63, 137.89, 147.53, 149.24, 161.23 ppm; HRMS (DI-
EI+) (m/z) observed: 223.1362 (D=+0.4 ppm); calcd for C16H17N [M+]:
223.1361.
4-(2-Pyridyl)-1-(2-thienyl)-1-butene (3 s): IR (neat): n˜ =3071, 2845, 1589,
1435, 957, 694 cmÀ1 1H NMR (CDCl3): d=2.62 (dt, J=7.0, 7.5 Hz, 2H),
;
2.94 (t, J=7.5 Hz, 2H), 6.11 (dt, J=15.5, 7.0 Hz, 1H), 6.54 (d, J=
15.5 Hz, 1H), 6.85 (d, J=3.5 Hz, 1H), 6.91 (dd, J=3.5, 5.0 Hz, 1H), 7.07
(d, J=5.0 Hz, 1H), 7.10 (dd, J=5.0, 7.5 Hz, 1H), 7.15 (d, J=7.5 Hz, 1H),
7.58 (dd, J=7.5, 7.5 Hz, 1H), 8.54 ppm (d, J=5.0 Hz, 1H); 13C NMR
(CDCl3): d=32.97, 38.15, 121.29, 123.02, 123.42, 123.96, 124.58, 127.36,
129.81, 136.43, 143.01, 149.52, 161.32 ppm; HRMS (DI-EI+) (m/z) ob-
served: 215.0768 (D=À0.6 ppm); calcd for C13H13NS [M+]: 215.0769.
1-Phenyl-4-(5-methyl-2-pyridyl)-1-butene (3k): IR (neat): n˜ =2924, 2855,
1
1458, 1373, 964 cmÀ1; H NMR (CDCl3): d=2.30 (s, 3H), 2.64 (dt, J=6.8,
7.8 Hz, 2H), 2.92 (t, J=7.8 Hz, 2H), 6.26 (dt, J=16.0, 6.8 Hz, 1H), 6.41
(d, J=16.0 Hz, 1H), 7.06 (d, J=8.0 Hz, 1H), 7.16–7.21 (m, 1H), 7.25–
7.34 (m, 4H), 7.40 (d, J=8.0 Hz, 1H), 8.37 ppm (s, 1H); 13C NMR
(CDCl3): d=18.23, 33.39, 37.84, 122.49, 126.17, 127.08, 128.63, 130.01,
130.48, 130.63, 137.08, 137.89, 149.85, 158.46 ppm; elemental analysis:
calcd (%) for C16H17N: C 86.05, H 7.67; found: C 86.06, H 7.78.
3-Methyl-1-phenyl-4-(2-pyridyl)-1-butene (3m): IR (neat): n˜ =3024, 2963,
1
1589, 1435, 964, 748 cmÀ1; H NMR (CDCl3): d=1.12 (d, J=6.0 Hz, 3H),
Acknowledgements
2.81 (dd, J=6.0, 12.0 Hz, 1H), 2.83–2.90 (m, 1H), 2.92 (dd, J=6.0,
12.0 Hz, 1H), 6.18 (dd, J=7.0, 16.0 Hz, 1H), 6.30 (d, J=16.0 Hz, 1H),
7.08–7.13 (m, 2H), 7.14–7.20 (m, 1H), 7.25–7.32 (m, 4H), 7.57 (dt, J=
2.0, 7.5 Hz, 1H), 8.53 ppm (d, J=4.5 Hz, 1H); 13C NMR (CDCl3): d=
20.23, 37.92, 45.97, 121.25, 123.90, 126.20, 127.06, 128.61, 128.66, 135.72,
136.24, 137.89, 149.46, 160.71 ppm; HRMS (DI-EI+) (m/z) observed:
223.1364 (D=+1.5 ppm); calcd for C16H17N [M+]: 223.1361.
This work was supported by Grants-in-Aid for Scientific Research and
GCOE Research from JSPS.
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1-(4-Methylphenyl)-4-(2-pyridyl)-1-butene (3n): IR (neat): n˜ =3017,
1
2924, 2855, 1589, 1435, 964, 733 cmÀ1; H NMR (CDCl3): d=2.31 (s, 3H),
2.65 (dt, J=7.0, 7.5 Hz, 2H), 2.96 (t, J=7.5 Hz, 2H), 6.21 (dt, J=15.5,
7.0 Hz, 1H), 6.39 (d, J=15.5 Hz, 1H), 7.09 (d, J=8.0 Hz, 2H), 7.11 (dd,
J=5.0, 8.0 Hz, 1H), 7.16 (d, J=8.0 Hz, 1H), 7.22 (d, J=8.0 Hz, 2H), 7.58
(dd, J=8.0, 8.0 Hz, 1H), 8.55 ppm (d, J=5.0 Hz, 1H); 13C NMR
(CDCl3): d=21.30, 33.24, 38.42, 121.25, 123.05, 126.08, 128.82, 129.33,
130.57, 135.08, 136.42, 136.83, 149.53, 161.59 ppm; elemental analysis:
calcd (%) for C16H17N: C 86.05, H 7.67; found: C 86.24, H 7.84.
[3] M. Lautens, A. Roy, K. Fukuoka, K. Fagnou, B. Martin-Matute, J.
Am. Chem. Soc. 2001, 123, 5358–5359.
1-(2-Methylphenyl)-4-(2-pyridyl)-1-butene (3o): IR (neat): n˜ =3402,
[4] For rhodium-catalyzed addition of arylboronic acids to alkynyl aza-
heteroaromatic compounds, see: a) M. Lautens, M. Yoshida, J. Org.
Chem. 2003, 68, 762–769; b) E. Genin, V. Michelet, J.-P. GenÞt, Tet-
rahedron Lett. 2004, 45, 4157–4161; c) E. Genin, V. Michelet, J.-P.
GenÞt, J. Organomet. Chem. 2004, 689, 3820–3830.
1
3017, 2361, 1589, 1435, 964, 748 cmÀ1; H NMR (CDCl3): d=3.26 (s, 3H),
2.68 (dt, J=7.0, 7.5 Hz, 2H), 2.98 (t, J=7.5 Hz, 2H), 6.12 (dt, J=16.0,
7.0 Hz, 1H), 6.59 (d, J=16.0 Hz, 1H), 7.09–7.15 (m, 4H), 7.17 (d, J=
7.5 Hz, 1H), 7.38 (d, J=7.5 Hz, 1H), 7.59 (dd, J=7.5, 7.5 Hz, 1H),
8.55 ppm (d, J=5.0 Hz, 1H); 13C NMR (CDCl3): d=19.91, 33.49, 38.41,
121.25, 123.11, 125.71, 126.15, 127.07, 128.77, 130.28, 131.14, 135.17,
136.41, 137.03, 149.53, 161.53 ppm; HRMS (DI-EI+) (m/z) observed:
223.1363 (D=+1.1 ppm); calcd for C16H17N [M+]: 223.1361.
[5] R. Amengual, V. Michelet, J.-P. GenÞt, Tetrahedron Lett. 2002, 43,
5905–5908.
[6] Reviews: a) H. Yorimitsu, K. Oshima, Pure Appl. Chem. 2006, 78,
441–449; b) H. Shinokubo, K. Oshima, Eur. J. Org. Chem. 2004,
2081–2091; c) K. Oshima, Bull. Chem. Soc. Jpn. 2008, 81, 1–24.
[7] Recent examples: a) H. Someya, H. Ohmiya, H. Yorimitsu, K.
Oshima, Tetrahedron 2007, 63, 8609–8618; b) H. Someya, H.
1-(4-Methoxyphenyl)-4-(2-pyridyl)-1-butene (3p): m.p.: 56–588C. IR
(nujol): n˜ =2855, 2677, 2361, 1458, 1373, 1042 cmÀ1 1H NMR (CDCl3):
;
d=2.63 (dt, J=7.0, 7.5 Hz, 2H), 2.95 (t, J=7.5 Hz, 2H), 3.79 (s, 3H),
672
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Chem. Asian J. 2011, 6, 669 – 673

Cobalt-Catalyzed Addition of Styrylboronic Acids
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[8] Recent reviews on cobalt-catalyzed reactions by other groups: a) C.
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Received: April 19, 2010
Published online: July 21, 2010
Chem. Asian J. 2011, 6, 669 – 673
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