Nickel-catalyzed carbostannylation of alkynes with allyl-, acyl-, and alkynylstannanes: Stereoselective synthesis of trisubstituted vinylstannanes [6]

Full text of DOI:10.1021/ja992597s

J. Am. Chem. Soc. 1999, 121, 10221-10222
10221
Scheme 1
Nickel-Catalyzed Carbostannylation of Alkynes with
Allyl-, Acyl-, and Alkynylstannanes: Stereoselective
Synthesis of Trisubstituted Vinylstannanes
Eiji Shirakawa,*,† Kenji Yamasaki,‡ Hiroto Yoshida,‡ and
Tamejiro Hiyama*,‡
Graduate School of Materials Science
Japan AdVanced Institute of Science and Technology
Asahidai, Tatsunokuchi, Ishikawa 923-1292, Japan
Department of Material Chemistry
Graduate School of Engineering, Kyoto UniVersity
Sakyo-ku, Kyoto 606-8501, Japan
Table 1. Nickel-Catalyzed Carbostannylation of 1-Octyne (2a)
with Allyl(tributyl)tin (1a)a
ReceiVed July 22, 1999
conv
conv
Carbostannylation of internal alkynes should be one of the most
useful tools for stereoselective synthesis of olefins, since the
resulting trisubstituted vinylstannanes are readily converted into
various tetrasubstituted ethenes via various synthetic transforma-
tions.1 There have been, however, only a limited number of reports
on this synthesis subject.1b,2 Although Yamamoto and co-workers
have reported that allylstannanes add to terminal alkynes with
anti-selectivity when a Lewis acid catalyst is used, available
alkynes are limited to terminal ones.3 Anti-selective allylstannyl-
ation of alkynes is found also by Hosomi and co-workers and is
mediated by such a radical initiator as AIBN to give a mixture
of stereo- and regioisomers, the internal alkynes being restricted
to relatively electron-deficient ones.4 On the other hand, the
palladium-catalyzed alkynylstannylation of alkynes proceeds with
exclusive syn-selectivity and acceptable regioselectivity.5,6 How-
ever, the scope of the reaction is limited to alkynylstannanes and
relatively electron-deficient alkynes. Herein we report that the
nickel-catalyzed carbostannylation of alkynes has following superb
features: (1) a nickel(0) complex mediates the reaction of even
relatively electron-rich internal alkynes, (2) the reaction is
applicable not only to alkynylstannanes but also to acyl- and
allylstannanes, (3) syn-selectivity results also in allylstannylation
of alkynes, and (4) regioselectivities are much higher than the
palladium-catalyzed alkynylstannylation.
The catalytic activity of various nickel complexes was first
examined for the reaction of allyl(tributyl)tin (1a, R1 ) R2 ) H)
with 1-octyne (2a, R3 ) hexyl, R4 ) H) (Scheme 1). The
conversion of 1a and the ratio of carbostannylation products 3a
and 4a were readily monitored by 119Sn NMR; the results obtained
from the reaction carried out at 80 °C for 1 h are summarized in
Table 1. As can be readily seen, reaction with 5 mol % of bis-
(1,5-cyclooctadiene)nickel(0), Ni(cod)2, in toluene gave a 68:32
mixture of 3a and 4a in 85% conversion (entry 1).7 Polar solvents
accelerated the reaction at the slight expense of regioselectivity
(entries 2-4). Octane or pyridine as a solvent retarded the reaction
(entries 5 and 6). Use of triphenylphosphine (10 mol %) or
entry solvent (%)b 3a:4ab entry
solvent
(%)b 3a:4ab
1
2
3
toluene 85
68:32
58:42
60:40
4
5
6
1,4-dioxane 85
65:35
58:42
60:40
DMF
DME
92
91
octane
pyridine
70
20
a The reaction was carried out in a solvent (0.3 mL) at 80 °C using
allyl(tributyl)tin (0.46 mmol) and 1-octyne (1.38 mmol) for 1 h in the
presence of Ni(cod)2 (23 µmol). b Determined by 119Sn NMR.
Table 2. Nickel-Catalyzed Allylstannylation of Alkynesa
temp time yield
entry allylstannane alkyne (°C) (h) (%)b product(s) 3:4c
1
2d
3
4
5
6
7
8
9
1a
2a
2b
2c
2d
2e
2f
2g
2h
2i
80
80 14
80
100 12
100 12
100 14
100 40
100 14
5
93
80
0.5 77
3a, 4a
3b
64:36
-
-
3c
78
77
76
78
64
70
64
87
3d, 4d
3e
65:35
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
-
3f
3g
3h
100
100 14
80
8
3i
10
11
1b
1c
2e
2c
3j
3
3k
a The reaction was carried out in toluene (0.3 mL) using an
organostannane (0.46 mmol), an alkyne (1.38 mmol), and Ni(cod)2 (23
µmol). b Isolated yield based on the organostannane. c Determined by
119Sn NMR. d The reaction was carried out under an acetylene
atmosphere (1 atm).
N-(2-diphenylphosphinobenzylidene)-2-phenylethylamine (5)
(5 mol %), an efficient ligand for the palladium-catalyzed
alkynylstannylation of alkynes,5 inhibited the reaction.
The allylstannylation of various alkynes with Ni(cod)2 catalyst
was next studied in toluene (Scheme 1 and Table 2). Whereas
acetylene (2b) also reacted with 1a in good yield (entry 2),
phenylacetylene and ethyl propiolate did not give significant
amounts of carbostannylation products due to competitive self-
polymerization of the alkynes. In contrast, internal alkynes gave
good yields of the corresponding carbostannylation products,
irrespective of electron-withdrawing or -donating character of
substituent R3 and/or R4 (entries 3-9). Furthermore, a single
† Japan Advanced Institute of Science and Technology.
‡ Kyoto University.
(1) (a) Farina, V.; Krishnamurthy, V.; Scott, W. J. Org. React. 1997, 50,
1-652. (b) Davies, A. G. Organotin Chemistry; VCH: Weinheim, 1997. (c)
Pereyre, M.; Quintard, J.-P.; Rahm, A. Tin in Organic Synthesis; Butter-
worth: London, 1987.
(7) Configuration of the carbostannylation products was determined by
NMR studies (coupling constants and NOE) of the alkenylstannanes and/or
the alkenes obtained by protonolysis. For example, the stereochemistry of 3a
and 4a was determined on the basis of NOE (irradiation at the methine peak)
and the H-Sn coupling constant, as shown below. For the coupling constants
between tin and olefinic protons in alkenylstannanes, see: Leusink, A. J.;
Budding, H. A.; Marsman, J. W. J. Organomet. Chem. 1967, 9, 285-294.
(2) Multistep synthesis of trisubstituted vinylstannanes has been reported.
Wang, K. K.; Chu, K.-H.; Lin, Y.; Chen, J.-H. Tetrahedron 1989, 45, 1105-
1118.
(3) Asao, N.; Matsukawa, Y.; Yamamoto, Y. Chem. Commun. 1996, 1513-
1514.
(4) Miura, K.; Itoh, D.; Hondo, T.; Saito, H.; Ito, H.; Hosomi, A.
Tetrahedron Lett. 1996, 37, 8539-8542.
(5) Shirakawa, E.; Yoshida, H.; Kurahashi, T.; Nakao, Y.; Hiyama, T. J.
Am. Chem. Soc. 1998, 120, 2975-2976.
(6) Depending on the ligand, the palladium-catalyzed carbostannylation is
accompanied by dimerization of alkynes. Shirakawa, E.; Yoshida, H.; Nakao,
Y.; Hiyama, T. J. Am. Chem. Soc. 1999, 121, 4290-4291.
10.1021/ja992597s CCC: $18.00 © 1999 American Chemical Society
Published on Web 10/16/1999

10222 J. Am. Chem. Soc., Vol. 121, No. 43, 1999
Communications to the Editor
Table 4. Nickel-Catalyzed Alkynylstannylation of Alkynesa
Scheme 2
entry alkynylstannane alkyne time (h) yield (%)b product
1
2
3
4
5
9a
9b
9c
9d
9b
2a
2a
2a
2a
2j
24
4
10
36
5
72
82
70
56
79
10a
10b
10c
10d
10e
a The reaction was carried out in toluene (0.5 mL) at 80 °C using
an alkynylstannane (0.76 mmol) and an alkyne (2.3 mmol) in the
presence of a Ni(0) catalyst prepared in situ from Ni(acac)2 (38 µmol)
and a 1.5 M toluene solution of diisobutylaluminum hydride (76 µmol).
b Isolated yield based on the organostannane.
Table 3. Nickel-Catalyzed Acylstannylation of Alkynesa
entry acylstannane alkyne time (h) yield (%)b product(s) 7:8c
1
2
3
4
6a
2c
2e
2c
2e
2
65
61
66
81
7a
7b, 8b
7c
-
Scheme 4
1.5
1.5
2
83:17
-
6b
7d, 8d
64:36
a The reaction was carried out in toluene (0.3 mL) at 100 °C using
an organostannane (0.46 mmol) and an alkyne (0.69 mmol) in the
presence of Ni(cod)2 (23 µmol). b Isolated yield based on the orga-
nostannane. c Determined by 119Sn NMR.
Scheme 3
regioisomer formed in the reaction of unsymmetrical internal
alkynes except for ethyl 2-butynoate. The regioselectivity is
proved to be extremely sensitive to the type of R3 and/or R4: a
Bu3Sn group invariably adds to the carbon having a more electron-
withdrawing group. Crotyltin added to 1-phenyl-1-propyne with-
out any allylic rearrangement (entry 10). Methallyltin also gave
the corresponding carbostannylation product (entry 11).
The nickel catalyst was demonstrated to be effective also for
the acylstannylation of alkynes. For example, benzoyl(trimethyl)-
tin and piperidinocarbonyl(tributyl)tin reacted with 4-octyne or
1-phenyl-1-propyne stereoselectively with Ni(cod)2 catalyst,
giving (Z)-â-stannyl-R,â-unsaturated carbonyl compounds (Scheme
2 and Table 3). To the best of our knowledge, this is the first
example of acylstannylation of alkynes.
The carbostannylation reaction with alkynylstannanes is also
effected with a nickel(0) catalyst. Particularly, the one prepared
from Ni(acac)2 and diisobutylaluminum hydride (1:2 ratio)
(Scheme 3 and Table 4) was more effective than Ni(cod)2 for
this reaction. For example, phenylethynyl(tributyl)tin reacted with
1-octyne in the presence of 5 mol % of the in situ-generated Ni-
(0) catalyst (toluene, 80 °C, 24 h) to give (Z)-2-hexyl-4-phenyl-
1-tributylstannyl-1-buten-3-yne in 72% yield (entry 1). (Phenyl-
ethynyl)stannanes with a variety of substituents gave the
corresponding carbostannylation products (entries 2-4). The
alkynyl moiety of 1-ethynylcyclohexene solely reacted (entry 5).
It is noteworthy that the regioselectivity is perfect, in sharp
contrast to the palladium-catalyzed alkynylstannylation that always
gave mixtures of regioisomers.5 Internal alkynes failed to give
products, as was the case with palladium catalyst. Although
electron-deficient terminal alkynes were not suitable for the nickel
catalyst as in the allystannylation, the palladium catalyst can
complement the reaction of such substrates.5
The utility of the carbostannylation products derived from
internal alkynes is demonstrated by transformation of the car-
bostannylation products to tetrasubstituted ethenes (Scheme 4).
Dienylstannane 3f coupled with cinnamyl carbonate 11 or
4-iodonitrobenzene to give 1,4-diphenyl-1,4,7-octatriene 12 or 1,1-
diaryl-1,4-pentadiene 13; â-acylethenylstannane 7c afforded R,â-
unsaturated carboxamide 14 in good yields. Exclusive syn- and
high regioselectivities of the nickel-catalyzed carbostannylation
reaction readily allows one to synthesize tetrasubstituted ethenes
without troublesome separation of isomers. For example, the
reaction of 1-phenylpropyne with 1a followed by the Negishi
cyclization8 gave cyclopentenone 15 in 52% total yield.
In conclusion, we have disclosed that, in the presence of a
nickel catalyst, the carbostannylation of both electron-rich and
-deficient alkynes takes place with allyl- acyl- or alkynylstannanes
to give various alkenylstannanes stereo- and regioselectively. This,
coupled with the palladium-catalyzed reaction, has made multiply
substituted ethenes readily accessible with high stereospecificity.
Further studies on synthetic applications to various organostan-
nanes and unsaturated target compounds as well as on the reaction
mechanism are in progress in our laboratories.
Supporting Information Available: Detailed experimental proce-
dures including spectroscopic and analytical data (PDF). This material
is available free of charge via the Internet at http://pubs.acs.org.
JA992597S
(8) Negishi, E.; Miller, J. A. J. Am. Chem. Soc. 1983, 105, 6761-6763.