Nickel-catalysed bis-allylation of internal alkynes with triallylindium

Article abstract of DOI:10.1039/b603663e

The Ni-catalysed reaction of triallylindium with internal alkynes underwent bis-allylation to afford octa-1,4,7-trienes in high yield. The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b603663e

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Nickel-catalysed bis-allylation of internal alkynes with triallylindium
Tsunehisa Hirashita,* Kazuhiko Akutagawa, Toshiya Kamei and Shuki Araki
Received (in Cambridge, UK) 10th March 2006, Accepted 20th April 2006
First published as an Advance Article on the web 10th May 2006
DOI: 10.1039/b603663e
The Ni-catalysed reaction of triallylindium with internal
alkynes underwent bis-allylation to afford octa-1,4,7-trienes in
high yield.
Table 1 Reaction of triallylindium with 1-phenylprop-1-yne
Addition of allylindium reagents (allylindation) to terminal alkynes
provides linear- or branch-type 1,4-dienes depending on the
existence or absence of a chelation functionality, in particular a
hydroxy group adjacent to the alkyne moiety:1 propargyl and
homopropargylic alcohols undergo allylindation in an anti-
Markovnikov fashion to afford linear-type 1,4-dienes, whereas
non-functionalized alkynes give branch-type 1,4-dienes. The
allylindation of inner alkynes, on the other hand, is limited to
alkynes bearing a hydroxy group or a trimethylsilyl group and
only the benzylindation of non-functionalized inner alkynes has
hitherto been documented.2 During our course of study for
allylindation, we found that non-functionalized inner alkynes
react with triallylindium in the presence of a nickel catalyst to give
octa-1,4,7-trienes selectively in high yields.
Yield (%)a
Entry
Catalyst (mol%)
1a
2a
3a
1
2
3
4
5
6
7
8
9
a
None
Ni(acac)2 (20)
Ni(acac)2 (50)
Ni(acac)2 (100)
Ni(acac)2 (20) + COD (40)
Ni(acac)2 (100) + COD (200)
Ni(acac)2 (100) + hexa-1,5-diene (200)
Ni(acac)2 (100) + PPh3 (100)
Ni(cod)2 (136)
0
25
58
72
34
83
78
1
0
4
7
4
6
0
4
2
3
0
0
0
0
0
0
0
1
0
55
Triallylindium, prepared from allylmagnesium bromide and
indium trichloride in THF, was allowed to react with 1-phenyl-
prop-1-yne and the results are summarized in Table 1.3 No
product was observed without catalyst and the starting alkyne was
recovered completely (entry 1). In the presence of Ni(acac)2, the
bis-allylated product 1a and the mono-allylated product 2a were
obtained (entry 2). The cis-geometry of 1a was determined by
Yields of products were determined by GC.
and diallylzinc were employed, a significant erosion of the yields
was observed (entries 3 and 4). Allylstannane gave no product
(entry 5). Allylmagnesium bromide, the precursor to triallylindium,
afforded 1a in only 20% yield (entry 6), suggesting that
the transmetallation into triallylindium is crucial for the successful
bis-allylation.
1
comparison with the H NMR in the literature.4 The yield of 1a
was increased by increasing the amount of Ni(acac)2 (entries 3 and
4). The addition of dienes proved useful for improving the yields
(entries 5–7), whereas the presence of PPh3 severely inhibited
the allylation (entry 8). Ni(cod)2 served as a catalyst for the
reaction (entry 9), while Pd(acac)2 and Pt(acac)2 did not promote
the bis-allylation.
Ikeda and co-workers have reported that the Ni-catalysed
reaction of terminal alkynes with allyl chloride and Me3Al gave the
three-component coupling products.6 In order to gain some
insights into the reaction mechanism of this bis-allylation, we
The bis-allylations with other alkynes were conducted under the
best conditions observed in Table 1. Oct-2-yne gave the
corresponding bis-allylated product 1b quantitatively (Table 2,
entry 1). Diphenyl acetylene also underwent the bis-allylation to
afford the octa-1,4,7-triene 1c in modest yield together with the
mono-allylated product 2c (entry 2).
Table 2 Reaction of triallylindium with alkynes
Next, we turned our attention to comparing a variety of
allylating agents for the bis-allylation (Table 3). Allylindium
diiodide gave 1a in 13% yield together with 2a in 7% yield (entry 1).
Allylindium sesquiiodide5 afforded similar results (entry 2). As
the best results were obtained with triallylindium among
allylindium reagents, we focused on other allylic metal reagents
bearing no halogen on the metal (entries 3–5). When triallylgallium
Entry
R1
R2
Yielda (%)
1
2
a
n-C5H11
Ph
Me
Ph
1b: 100
1c: 34 (40)b
Department of Materials Science and Engineering, Graduate School of
Engineering, Nagoya Institute of Technology, Gokiso, Showa, Nagoya,
466-8555, Japan. E-mail: hirasita@nitech.ac.jp; Fax: +81-52-735-5206;
Tel: +81-52-735-5206
2c: 6
b
Yields of products were determined by GC. Recovery of diphenyl
acetylene.
2598 | Chem. Commun., 2006, 2598–2600
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Table 3 Reaction of various allylic metals with alkynes
Yielda (%)
Entry
Allylic metal
1a
2a
3a
Recovery
b
1
2
3
4
5
6
a
(allyl)InI2
(allyl)3In2I3
13
9
18
5
0
20
7
11
5
5
0
0
0
1
2
0
1
b
50
21
9
19
97
1
c
(allyl)3Gad
(allyl)2Znd
(allyl)(n-Bu)3Sn
(allyl)MgBr
2
Yields of products were determined by GC. Prepared from allyl
iodide and InI. Prepared from allyl iodide and In. Prepared from
allylmagnesium bromide and MCln.
c
d
Scheme 1 Reaction mechanism for the formation of 1.
applied Me3In to the above reaction and found that the results
were similar to those observed in the case of Me3Al (Table 4). The
reaction mechanism involving Me3In is considered to be analogous
to that proposed for the reaction of Me3Al (Scheme 1): Initially a
p-allylnickel intermediate is formed from allyl chloride and an
active nickel(0) catalyst generated in situ by the reduction of
Ni(acac)2 with Me3In. The addition of the p-allylnickel(II) to an
alkyne gives a vinylic nickel intermediate, which undergoes a cross-
coupling reaction with Me3In affording the products and
regenerating the nickel(0) catalyst.
At present the reaction mechanism of the bis-allylation
remains unclear. p-Allylnickel intermediates have to be generated
from not allyl chloride but (allyl)3In. As a p-allylnickel reagent
can be prepared from nickel(II) with allyl Grignard bromide,4 a
transmetallation of (allyl)3In with Ni(acac)2 to a p-allylnickel
compound seems to be feasible. It is notable that (i) Ni(acac)2
showed, although not efficient, a catalytic activity (Table 1,
entries 2 and 3) and (ii) the reaction can start with a nickel(0)
catalyst (Table 1, entry 9). These results could be rationalized by
assuming that an alternative path generating a p-allylnickel
compound from nickel(0) and (allyl)3In operates during the
bis-allylation.7
As a logical progression from the above three-component
reaction, we initiated an approach to the bis-allylation product
by involving triallylindium instead of Me3In. The reaction of
1-phenylprop-1-yne, triallylindium and allyl chloride was
performed in the presence of Ni(acac)2 (20 mol%) in THF
at room temperature. The yield of the bis-allylation product
(17%) was, however, less than expected, showing that some
side reactions of the p-allylnickel intermediate, such as a cross-
coupling with triallylindium, take place prior to the addition to
the alkyne.
In conclusion, we have demonstrated that the reaction of
internal alkynes with triallylindium in the presence of nickel
catalyst affords the cis-bis-allylated products in high yield. Further
studies on details of this reaction and applications for other C–C
unsaturated bonds are in progress.
We are grateful to the Ministry of Education, Sports, Culture,
Science, and Technology, Japan Government, for Grant-in-Aid
for Scientific Research, No. 14340195 for financial support.
Table 4 Reaction of trimethylindium and allyl chloride with alkynesa
Notes and references
1 S. Araki, A. Imai, K. Shimizu and Y. Butsugan, Tetrahedron Lett., 1992,
33, 2581; S. Araki, A. Imai, K. Shimizu, M. Yamada, A. Mori and
Y. Butsugan, J. Org. Chem., 1995, 60, 1841; B. C. Ranu and A. Majee,
Chem. Commun., 1997, 1225; G. Engstrom, M. Morelli, C. Palomo and
T. Mitzel, Tetrahedron Lett., 1999, 40, 5967; E. Klaps and W. Schmid, J.
Org. Chem., 1999, 64, 7537; M. M. Salter and S. Sardo-Inffiri, Synlett,
2002, 2068.
2 N. Fujiwara and Y. Yamamoto, J. Org. Chem., 1997, 62, 2318.
3 Representative experimental procedure (Table 1, entry 6): All reactions
were performed under argon atmosphere. 1. Preparation of In(allyl)3: To
a solution of InCl3 (0.22 g, 1.0 mmol) in THF (5.0 mL), allylmagnesium
bromide (1.0 M, 3.0 mL, 3.0 mmol, Et2O solution) was added at 278 uC.
The reaction mixture was kept at the temperature for 1 h and another 1 h
at room temperature before use. 2. Reaction of alkyne with triallylindium:
Ni(acac)2 was obtained from Ni(acac)2?2H2O (150 mg, 0.50 mmol) by
heating with a heat gun in vacuo. To a solution of Ni(acac)2 in THF
(5.0 mL), the aforementioned solution of triallylindium (1.0 mmol),
1-phenylprop-1-yne (62 mL, 0.50 mmol), PhCH2Ph (10 mL, standard
material), and cycloocta-1,4-diene (125 mL, 1.0 mmol) were added at 0 uC.
Entry
R1
R2
Time/h
Yield (%) (2 : 3)b
1
2
a
n-C6H13
Ph
H
Me
4
24
78 (89 : 11)
51 (91 : 9)
The reactions were performed with acetylene (1.1 mmol), Me3In
(1.5 mmol), allyl chloride (1.0 mmol) and Ni(acac)2 (5 mol%).
Yields and the ratios of products were determined by GC.
b
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The reaction mixture was refluxed for 16 h and the reaction was
quenched with 1 M HCl (5.0 mL). The products were extracted with
ether and washed with water and brine, and dried over Na2SO4. The
yields were determined by GC analysis.
5 S. Araki, H. Ito and Y. Butsugan, J. Org. Chem., 1988, 53, 1831.
6 S. Ikeda, H. Miyashita and Y. Sato, Organometallics, 1998, 17, 4316.
7 A referee has suggested a possibility that triallylindium undergoes a
disproportionation into In(allyl)4 and In(allyl)2 to explain the
formation of p-allylnickel from triallylindium.
2
+
4 J. J. Eisch and G. A. Damasevitz, J. Organomet. Chem., 1975, 96, C19.
2600 | Chem. Commun., 2006, 2598–2600
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