Nickel-catalysed acylstannylation of 1,2-dienes: Synthesis and reactions of α-(acylmethyl)vinylstannanes

Article abstract of DOI:10.1039/b008190f

Bis(cycloocta-1,5-diene)nickel was found to be an effective catalyst for the acylstannylation of 1,2-dienes to give a wide variety of α-(acylmethyl)vinylstannanes, which were transformed to variously substituted conjugated and unconjugated enones by carbo

Full text of DOI:10.1039/b008190f

Nickel-catalysed acylstannylation of 1,2-dienes: synthesis and reactions of
a-(acylmethyl)vinylstannanes
Eiji Shirakawa,*a Yoshiaki Nakaob and Tamejiro Hiyama*b
a Graduate School of Materials Science, Japan Advanced Institute of Science and Technology, Asahidai,
Tatsunokuchi, Ishikawa, 923-1292, Japan
b Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto, 606-8501,
Japan
Received (in Cambridge, UK) 10th October 2000, Accepted 26th October 2000
First published as an Advance Article on the web 23rd January 2001
Bis(cycloocta-1,5-diene)nickel was found to be an effective
catalyst for the acylstannylation of 1,2-dienes to give a wide
variety of a-(acylmethyl)vinylstannanes, which were trans-
formed to variously substituted conjugated and uncon-
jugated enones by carbon–carbon bond forming reactions.
being lowered by an electron-withdrawing substituent on the
aromatic ring (entries 4–6). The reaction of 1-methoxypropa-
1,2-diene (2g) proceeded with the benzoyl group of 1a adding
mainly at the carbon having the methoxy group albeit in a low
yield (entry 7). The tributylstannyl derivative (1b) of 1a also
gave the acylstannylated product (entry 8). Tributyl(propa-
noyl)tin (1c) also added to various 1,2-dienes (entries 9–12).
Noteworthy is that 2g reacted with 1c better than with 1a to
afford acylstannylation product 3l in a higher yield. Amino-
carbonylstannane 1d reacted with allene (2a) in a low yield
(entry 13).
Disubstituted allenes also participated in the acylstannylation
(Scheme 3). Acylstannanes 1a and 1c added to 3-methylbuta-
1,2-diene (2h) with high regioselectivities. In addition, nona-
4,5-diene (2i) also underwent the reaction, giving a stereo-
isomeric mixture of 3p or 3q.
The catalytic cycle is considered to be initiated by the
oxidative addition of an acylstannane to a nickel(0) complex as
is the case with the nickel-catalysed acylstannylation of
1,3-dienes, since the decarbonylation of acylstannanes was
similarly observed as a side reaction.3 Although the succeeding
pathway remains yet to be clarified, two plausible catalytic
cycles leading to the main products are presented in Scheme 4.
In any event, the stannyl group invariably attacks the allene
central carbon. In Cycle A, coordination of the less hindered
double bond of 1,2-diene 2 on the nickel atom of oxidative
adduct 4 followed by insertion to the Ni–Sn bond (stannylnick-
elation) affords the acylstannylation product through p-allyl-
nickel complex 6. According to Cycle B, the more hindered
double bond of 2 coordinates on the nickel and then inserts to
Alkenylstannanes are one of the most versatile synthetic
reagents, since they can be transformed to various olefinic
compounds through the reaction with organic electrophiles, e.g.
the palladium-catalysed cross-coupling reaction.1 Although the
reaction of other alkenylmetals with stannyl halides provides an
easy access to alkenylstannanes, this synthetic method cannot
be applied to those having such a reactive substituent as
carbonyl. Carbostannylation of alkynes has grown to be a
powerful alternative route to alkenylstannanes, especially
multi-substituted vinylstannanes (Scheme 1, a).2 Herein we
disclose that acylstannanes add to 1,2-dienes in the presence of
a nickel catalyst3 to give a-(acylmethyl)vinylstannanes4 as
main products (Scheme 1, b) and the resulting alkenylstannanes
can be transformed to variously conjugated and/or uncon-
jugated enones. To the best of our knowledge, this is the first
demonstration of the transition metal-catalysed addition of a
carbon–metal bond of organometallic compounds to
1,2-dienes.5,6
Scheme 1
Table 1 Nickel-catalysed acylstannylation of 1,2-dienesa
Acylstannylation of monosubstituted allenes were carried out
in the presence of a nickel catalyst (Scheme 2 and Table 1). The
following procedure is representative (entry 1). A mixture of
trimethyl(benzoyl)tin (1a) and 5 mol% of Ni(cod)2 in toluene
was heated at 50 °C for 1.5 h under an atmosphere of propa-
1,2-diene (2a) to give 1-phenyl-3-trimethylstannylbut-3-en-
1-one (3a) in 64% yield.7 Analysis of the reaction mixture by
119Sn NMR revealed that the ratio of 3a and (E)-1-phenyl-
3-trimethylstannylbut-2-en-1-one, derived probably through
the isomerization of 3a, was 97+3, although trimethyl(phe-
nyl)tin, the decarbonylated product of 1a, was obtained in a
small amount. Addition of 1a to hepta-1,2-diene (2b) took place
mainly at the internal C–C double bond to give 3b in 79% yield
(entry 2).8 Similar regioselectivity was observed in the reaction
of 4,4-dimethylpenta-1,2-diene (2c) (entry 3). Arylallenes also
participated in the acylstannylation with the selectivity of 3
Acylstannane
Entry R1 R2
1,2-Diene
R3
Time/ Yield of Prod 3+
3 (%)b othersc
h
1d Ph
Me (1a) H (2a)
Me (1a) Bu (2b)
Me (1a) t-Bu (2c)
1.5 64
1.5 79
1.5 59
3a
97+3
2
3
4
5
6
7
Ph
Ph
Ph
Ph
Ph
Ph
3b
3c
3d
3e
3f
3g
3h
3i
89+11
86+14
78+22
77+23
66+34
93+7
Me (1a) 4-MeOC6H4 (2d) 2
50
53
35
26
48
Me (1a) Ph (2e)
Me (1a) 4-CF3C6H4 (2f)
Me (1a) MeO (2g)
Bu (1b) H (2a)
2
2
2
4
8d Ph
9d Et
79+21
94+6
Bu (1c) H (2a)
1.5 67
53
10e Et
11e Et
12e Et
Bu (1c) Bu (2b)
Bu (1c) Ph (2e)
Bu (1c) MeO (2g)
2
3j
3k
3l
89+11
79+21
95+5
3.5 43
2.5 48
13d,f (CH2)5N Me (1d) H (2a)
2
25
3m
—
g
a The reaction was carried out in toluene (0.4 mL) at 50 °C using an
acylstannane (0.30 mmol), a 1,2-diene (0.90 mmol) and Ni(cod)2 (15 mmol).
b Isolated yield based on the organostannane. c Determined by 119Sn NMR.
d The reaction was carried out under an allene atmosphere (1 atm). e The
reaction was carried out at 80 °C. f The reaction was carried out at 100 °C
in the presence of 60 mmol of Ni(cod)2. g Accompanied by a complex
mixture of the products other than 3m.
Scheme 2
DOI: 10.1039/b008190f
Chem. Commun., 2001, 263–264
This journal is © The Royal Society of Chemistry 2001
263

Scheme 3
Scheme 5 Reagents and conditions: i, 4-EtOCO–C6H4–I (8, 1.0 equiv), 2.5
mol% of Pd2(db a)3, NMP, 30 °C, 15 h (from 3i to 9) or 10 h (from 14 to
15); ii, NaH (0.2 equiv.), THF, rt, 4 h (from 3i to 10) or 3 h (from 9 to 12);
iii, 8 (1.0 equiv.), 5 mol% of Pd2(dba)3, NMP, 30 °C, 69 h; iv, PhCOCl (1.0
equiv.), 2.5 mol% of Pd2(dba)3, NMP, 30 °C, 8 h; v, Me–I (3.0 equiv.) THF,
rt, 17 h.
the C–Ni bond of 4 (acylnickelation), giving the product via
alkenylnickel 7.9 The results that the acylstannylation of nona-
4,5-diene (2i) gave a mixture of stereoisomers should give us a
clue to discriminate the reaction mechanism. In the case that the
reaction with 2i follows Cycle B, only (E)-3p or 3q should be
provided through syn-addition of the C–Ni bond to the C–C
double bond and stereo-retained reductive elimination. As this
was not the case, Cycle A appears to be more plausible,
although it is unclear yet why reductive elimination from 6 takes
place mainly at the more hindered carbon of the allyl moiety.
unsaturated substrates and organostannanes are in progress in
our laboratories.
We thank the Ministry of Education, Science, Sports and
Culture, Japan, for the Grant-in-Aids for COE Research on
Elements Science, No. 12CE2005 and Scientific Research,
No.12750758. E. S. thanks the Asahi Glass Foundation for
financial support.
Notes and references
1 (a) A. G. Davies, Organotin Chemistry, VCH, Weinheim, 1997; (b) V.
Farina, V. Krishnamurthy and W. J. Scott, Org. React., 1997, 50, 1.
2 Lewis acid-catalysed reaction: (a) N. Asao, Y. Matsukawa and Y.
Yamamoto, Chem. Commun., 1996, 1513; (b) Y. Matsukawa, N. Asao,
H. Kitahara and Y. Yamamoto, Tetrahedron, 1999, 55, 3779; with a
radical initiator: (c) K. Miura, D. Itoh, T. Hondo, H. Saito, H. Ito and A.
Hosomi, Tetrahedron Lett., 1996, 37, 8539; transition metal-catalysed
reaction: (d) E. Shirakawa, H. Yoshida, T. Kurahashi, Y. Nakao and T.
Hiyama, J. Am. Chem. Soc., 1998, 120, 2975; (e) E. Shirakawa, H.
Yoshida, Y. Nakao and T. Hiyama, J. Am. Chem. Soc., 1999, 121, 4290;
(f) E. Shirakawa, K. Yamasaki, H. Yoshida and T. Hiyama, J. Am.
Chem. Soc., 1999, 121, 10221; (g) E. Shirakawa, H. Yoshida, Y. Nakao
and T. Hiyama, Org. Lett., 2000, 2, 2209.
3 We reported the nickel-catalysed acylstannylation of 1,3-dienes: E.
Shirakawa, Y. Nakao, H. Yoshida and T. Hiyama, J. Am. Chem. Soc.,
2000, 122, 9030.
Scheme 4
4 a-Substituted vinylstannanes are available by stannylcupration of
alkynes followed by quenching the resulting C–Cu bond with methanol:
J. A. Carbezas and A. C. Oehlschlager, Synthesis, 1994, 432.
5 There have been many reports on the transition metal-catalysed
bismetalation of 1,2-dienes: for example, M. Suginome, Y. Ohmori and
Y. Ito, Synlett, 1999, 1567 and references cited therein.
6 The palladium-catalysed three component coupling of 1,2-dienes,
distannanes and organic iodides is reported to provide allylstannanes:
F.-Y. Yang, M.-Y. Wu and C.-H. Cheng, Tetrahedron Lett., 1999, 40,
6055.
The applicability of the acylstannylation products was
demonstrated by the transformation of 3i to a wide variety of
enones (Scheme 5). The reaction of 3i with ethyl 4-iodo-
benzoate (8) in the presence of 2.5 mol% of Pd2(dba)3 gave the
corresponding coupling product 9 in 91% yield10 without cine-
substitution.1b Conjugated b-arylenone 11 was obtained11 by
cross-coupling reaction with 8 after isomerization of 3i to 10 by
20 mol% of sodium hydride, whereas the corresponding (E)-
isomer 12 was obtained by base-catalysed isomerization of 9.
The cross-coupling of 3i with benzoyl chloride proceeded to
give 83% yield of enedione 13. Stannylenone 3i reacted with
iodomethane in the presence of sodium hydride, giving
dimethylation product 14, which was subjected to the cross-
coupling reaction with 8 to afford arylenone 15. Thus, variously
substituted conjugated and unconjugated enones were synthe-
sized from a single acylstannylation product.
7 The reaction conditions are essentially identical with those used in the
nickel-catalysed carbostannylation of alkynes, see ref. 2e.
8 The reaction mixture contains 2-methylene-1-phenyl-3-trimethylstan-
nylheptan-1-one (5% yield) and (E)-1-phenyl-3-trimethylstannyloct-
3-en-1-one (4% yield). Although we did not characterize the minor
isomer(s) in the following entries thoroughly, peak(s) in 119Sn NMR
was always observed at 242.2 to 14.2 ppm, being attributed to an
alkenyl- or allyl(trialkyl)stannane.
9 Platinum-catalysed diboration of monosubstituted allenes, which is
considered to proceed via an alkenylplatinum complex similar to 7, gave
the (Z)-isomer stereoselectively. T. Ishiyama, T. Kitano and N. Miyaura,
Tetrahedron Lett., 1998, 39, 2357.
In conclusion, we have demonstrated that the acylstannyla-
tion of 1,2-dienes readily takes place to give a-(acylmethyl)-
vinylstannanes, which were transformed to a wide variety of
conjugated and unconjugated enones. Studies on details of the
mechanism as well as synthetic applications to various
10 Conjugated arylenone 12 was also generated in 5% yield.
11 The reaction mixture contains 12 (8% yield).
264
Chem. Commun., 2001, 263–264