Preparation of multisubstituted allenes from allylsilanes

Article abstract of DOI:10.1021/jo050142h

A three-step route of converting allylsilanes to functionalized allenes was developed. Thermal decomposition of 1,1-dibromo-2-(silylmethyl)cyclopropanes, which were quantitatively prepared by treatment of allylsilane derivatives with CHBr₃/KO

Full text of DOI:10.1021/jo050142h

Preparation of Multisubstituted Allenes from Allylsilanes
Masamichi Ogasawara,* Yonghui Ge, Koichi Uetake, Liyan Fan, and Tamotsu Takahashi*
Catalysis Research Center and Graduate School of Pharmaceutical Sciences, Hokkaido University, and
SORST, Japan Science and Technology Agency (JST), Kita-ku, Sapporo 001-0021, Japan
ogasawar@cat.hokudai.ac.jp; tamotsu@cat.hokudai.ac.jp
Received January 24, 2005
A three-step route of converting allylsilanes to functionalized allenes was developed. Thermal
decomposition of 1,1-dibromo-2-(silylmethyl)cyclopropanes, which were quantitatively prepared by
treatment of allylsilane derivatives with CHBr3/KOtBu, afforded substituted 2-bromo-1,3-butadienes
with elimination of bromosilanes. The Pd-catalyzed reaction of the bromodienes with soft
nucleophiles gave the allene derivatives. Previously inaccessible tri- and tetrasubstituted allenes
can be prepared by this method as well.
SCHEME 1
Introduction
Allenes have received considerable attention as im-
portant synthetic intermediates in organic synthesis.1
Due to the cumulated propadienyl structure, allenes
possess unique electronic and steric properties, and these
facts make allenes attractive substrates/reagents for
transition-metal-catalyzed/-mediated reactions.2 Although
many interesting transformations of allenes have been
developed recently, their synthetic usefulness is clearly
associated with convenient methods of preparing allenic
compounds.1,3
Recently, we have reported a three-step conversion of
a variety of aldehydes into functionalized allenes utilizing
two Pd-catalyzed reactions (Scheme 1),4 and the final step
of the reaction sequence has been developed into a
catalytic asymmetric reaction giving enantiomerically
enriched axially chiral allenes.5 The key compounds of
the allene synthesis are 2-bromo-1,3-butadiene deriva-
tives. Besides the allene preparation, 2-bromo-1,3-buta-
dienes have been demonstrated as useful synthons in
other organic transformations, such as Diels-Alder reac-
tions6 and stereoselective preparation of conjugated poly-
(1) (a) Taylor, D. R. Chem. Rev. 1967, 67, 317. (b) Rutledge, T. F.
Acetylenes and Allenes; Reinhold: New York, 1969. (c) Patai, S. The
Chemistry of Ketenes, Allenes, and Related Compounds; Wiley: Chich-
ester, 1980. (d) Landor, S. R. The Chemistry of the Allenes; Academic
Press: London, 1982. (e) Coppola, G. M.; Schuster, H. F. Allenes in
Organic Synthesis; Wiley: New York, 1984. (f) Krause, N.; Hashmi,
A. S. K. Modern Allene Chemistry; Wiley-VCH: Weinheim, 2004. (g)
Pasto, D. J. Tetrahedron 1984, 40, 2805. (h) Marshall, J. A. Chem.
Rev. 1996, 96, 31. (i) Wang, K. K. Chem. Rev. 1996, 96, 207. (j) Lu, X.;
Zhang, C.; Xu, Z. Acc. Chem. Res. 2001, 34, 535. (k) Tius, M. A. Acc.
Chem. Res. 2003, 36, 284. (l) Brandsma, L.; Nedolya, N. A. Synthesis
2004, 735.
(2) (a) Yamamoto, Y.; Radhakrishnan, U. Chem. Soc. Rev. 1999, 28,
199. (b) Hashmi, A. S. K. Angew. Chem., Int. Ed. 2000, 39, 3590. (c)
Zimmer, R.; Dinesh, C. U.; Nandanan, E.; Khan, F. A. Chem. Rev. 2000,
100, 3067. (d) Ma, S.; Li, L. Synlett 2001, 1206. (e) Ma, S. In Handbook
of Organopalladium Chemistry for Organic Synthesis; Negishi, E., Ed.;
Wiley-Interscience: New York, 2002; p 1491. (f) Ma, S. Acc. Chem.
Res. 2003, 36, 701. (g) Ma, S. Eur. J. Org. Chem. 2004, 1175.
(3) (a) Sandler, S. R.; Karo, W. Organic Functional Group Prepara-
tions, 2nd ed.; Academic Press: Orlando, 1986; Vol. II, p 1. (b) Sydnes,
L. K. Chem. Rev. 2003, 103, 1133. (c) Brandsma, L. Synthesis of
Acetylenes, Allenes and Cumulenes; Elsevier: Oxford, 2004. (d) Miesch,
M. Synthesis 2004, 746.
(4) (a) Ogasawara, M.; Ikeda, H.; Hayashi, T. Angew. Chem., Int.
Ed. 2000, 39, 1042. (b) Ogasawara, M.; Ikeda, H.; Nagano, T.; Hayashi,
T. Org. Lett. 2001, 3, 2615.
(5) (a) Ogasawara, M.; Ikeda, H.; Nagano, T.; Hayashi, T. J. Am.
Chem. Soc. 2001, 123, 2089. (b) Ogasawara, M.; Ueyama, K.; Nagano,
T.; Mizuhata, T.; Hayashi, T. Org. Lett. 2003, 5, 217.
(6) For recent examples, see: (a) Roush, W. R.; Koyama, K.; Curtin,
M. L.; Moriarty, K. J. J. Am. Chem. Soc. 1996, 118, 7502. (b) Tsirk,
A.; Gronowitz, S.; Hornfeldt, A. B. Tetrahedron 1998, 54, 9529. (c)
Magnus, P.; Westwood, N.; Spyvee, M.; Frost, C.; Linnane, P.; Tavares,
F.; Lynch, V. Tetrahedron 1999, 55, 6435. (d) Abe H.; Aoyagi, S.;
Kibayashi, C. J. Am. Chem. Soc. 2000, 122, 4583.
10.1021/jo050142h CCC: $30.25 © 2005 American Chemical Society
Published on Web 04/14/2005
J. Org. Chem. 2005, 70, 3871-3876
3871

Ogasawara et al.
SCHEME 2
SCHEME 3
enes.7 Most of the previously reported preparation of
2-bromo-1,3-butadienes has involved regioselective cross-
coupling reactions of 1,1-dibromoolefins.4a,7-9 However,
1,1-disubstituted bromodienes are not accessible by the
route shown in Scheme 1 (vide infra). This fact restricts
preparation of the corresponding 1,1-disubstituted al-
lenes by the method shown in Scheme 1.
Here we report a high-yield route to the bromobuta-
diene derivatives from substituted allylsilanes. The route
described in this paper enables us to prepare 1,1-
disubstituted-2-bromo-1,3-butadienes, and thus, the mul-
tisubstituted allenes are now within our reach.
It has been known that thermolysis of gem-dihalo-
cyclopropanes affords 2-halo-1,3-diene derivatives via
ring-opening and 1,4-dehydrohalogenation when the
compounds have hydrogen(s) in an appropriate exocyclic
position.6c,10 However, the critical problem of this method
is selectivity in the thermolysis: the products were
obtained as mixtures of several isomers in many cases if
gem-dihalocyclopropanes have more than one chemically
inequivalent hydrogen atoms on exocyclic R-carbons
(Scheme 2). In addition, the thermolysis often requires
vigorous reaction conditions (e.g., vacuum pyrolysis at
ca. 500 °C),10c which may induce thermal rearrangement
of the products. A useful strategy of solving these
problems is utilizing a silyl group as a potential leaving
group in the thermolysis reaction, which might increase
selectivity of the reaction and enable to perform the
reaction under milder conditions.11
derivatives from allylsilanes12 is summarized in Scheme
3 and Table 1. Treatment of allylsilanes 1 with an
equimolar mixture of CHBr3 and KOtBu (3 equiv with
respect to 1) in hexane afforded 1,1-dibromo-2-(silylm-
ethyl)cyclopropanes 2 in nearly quantitative yields
(Scheme 3).13
When thermolysis of dibromocyclopropane 2a was
performed under vacuum without solvent (150-180 °C,
bath temperature),11b ring opening and 1,4-debromosily-
lation took place as expected and 1-phenyl-2-bromo-1,3-
butadiene 3a was obtained as a single isomer in 66%
yield by vacuum distillation (Table 1, entry 1). The
geometry of 3a was determined to be (Z) by comparison
of its 1H and 13C NMR spectra with those reported
previously.4a,14 GC-MS and NMR analysis of the residue
of the vacuum distillation revealed that major byproducts
in the thermolysis were an isomeric mixture of dehydro-
bromination species 4a (Scheme 4). It was found that the
undesirable dehydrobromination was nearly completely
suppressed when the thermal decomposition of 2a was
carried out in DMF. The thermolysis of 2a in DMF
proceeded within 15 min at 150 °C, and 3a was obtained
in 81% isolated yield after usual workup (entry 2). For
the thermolysis of the dibromocyclopropane 2 with alkyl
substituents at the R1, R2, and/or R3 positions (Scheme
3), the reactions at lower temperature (110 °C) generally
afforded the corresponding bromodiene 3 in higher yields
although the reactions took longer to reach completion.
While the bromodiene 3a prepared from 2a without
solvent consisted of the (Z)-isomer only, the thermolysis
of 2a in DMF afforded 3a as a mixture of (Z)- and (E)-
isomers with a (Z)/(E) ) 67/33 ratio. Analogous stereo-
selectivity was seen in the thermal decomposition of 2b:
while 3b was obtained in 22% yield as a pure (Z)-isomer
by the reaction of 2b without solvent (entry 3), the
reaction in DMF at 110 °C gave a (Z)/(E)-mixture of 3b
((Z)/(E) ) 86/14) in 86% yield (entry 4). The two isomers
in 3a and 3h were separable by silica gel column
Results and Discussion
Preparation of 2-Bromo-1,3-diene Derivatives
from Allylsilanes. Preparation of 2-bromo-1,3-butadiene
(7) (a) Xu, C.; Negishi, E. Tetrahedron Lett. 1999, 40, 431. (b) Zeng,
X.; Hu, Q.; Qian, M.; Negishi, E. J. Am. Chem. Soc. 2003, 125, 13636.
(c) Zeng, X.; Qian, M.; Hu, Q.; Negishi, E. Angew. Chem., Int. Ed. 2004,
43, 2259.
(8) (a) Roush, W. R.; Moriarty, K. J.; Brown, B. B. Tetrahedron Lett.
1990, 31, 6509. (b) Shen, W.; Wang, L. J. Org. Chem. 1999, 64, 8873.
(9) For other reports on preparation of 2-bromo-1,3-dienes, see: (a)
Gronowitz, S.; Hallberg, A.; Nikitidis, G. Tetrahedron 1987, 43, 4793.
(b) Alper, H.; Vasapollo, G. Tetrahedron Lett. 1989, 30, 2617. (c)
Horva´th, A.; Ba¨ckvall, J.-E. J. Org. Chem. 2001, 66, 8120. (d) Ma, S.;
Wang, G. Tetrahedron Lett. 2002, 43, 5723.
(10) (a) Sandler, S. R. J. Org. Chem. 1968, 12, 4537. (b) Weyerstahl,
P.; Klamann, D.; Finger, D.; Fligge, M.; Nerdel, F.; Buddrus, J. Chem.
Ber. 1968, 101, 1303. (c) Nerdel, F.; Hentschel, P.; Brodowski, W.;
Buddrus, J. Liebigs Ann. Chem. 1971, 746, 6. (d) Molchanov, A. P.;
Kostikov, R. R. Zh. Org. Khim. 1989, 25, 2533; J. Org. Chem. USSR
1990, 25, 2272. (e) Werstiuk, N. H.; Roy, C. D. Tetrahedron Lett., 2001,
42, 3255 and references therein.
(12) For preparation of allylsilanes used in this study, see: (a)
Colvin, W. E. Silicon Reagents in Organic Synthesis; Academic Press:
London, 1988; Chapter 5, pp 25-37. (b) Fleming, I.; Pearce, A. J. Chem.
Soc., Perkin Trans. 1 1981, 251. (c) Negishi, E.; Luo, F.-T.; Rand, C.
L. Tetrahedron Lett. 1982, 23, 27. (d) Narayanan, B. A.; Bunnelle, W.
H. Tetrahedron Lett. 1987, 28, 6261. (e) Okamoto, S.; Tani, K.; Sato,
F.; Sharpless, K. B.; Zargarian, D. Tetrahedron Lett. 1993, 34, 2509.
(f) Denmark, S. E.; Fu, J. Org. Lett. 2002, 4, 1951.
(11) For preparation of 2-halo-1,3-butadienes with similar strategy,
see: (a) Seyferth, D.; Jula, T. J. Am. Chem. Soc. 1968, 90, 2938. (b)
Schlosser, M.; Dahan, R.; Cottens, S. Helv. Chim. Acta 1984, 67, 284.
(c) Mitani, M.; Kobayashi, Y.; Koyama, K. J. Chem. Soc., Perkin Trans.
1 1995, 653. (d) Roux, M.; Santelli, M.; Parrain, J.-L. Org. Lett. 2000,
2, 1701.
(13) (a) Creary, X.; Jiang, Z.; Butchko, M.; McLean, K. Tetrahedron
Lett. 1996, 37, 579. (b) Lahrech, M.; Hacini, S.; Parrain, J.-L.; Santelli,
M. Tetrahedron Lett. 1997, 38, 3395. (c) Fedorynski, M. Chem. Rev.
2003, 103, 1099.
(14) Krijnen, E. S.; Zuilhof, H.; Lodder, G. J. Org. Chem. 1994, 59,
8139.
3872 J. Org. Chem., Vol. 70, No. 10, 2005

Preparation of Multisubstituted Allenes from Allylsilanes
TABLE 1. Preparation of 2-Bromo-1,3-butadienes 3 from Allylsilane 1
entry
allylsilane 1
yield of 2a (%)
thermolysis conditions
yield of 3a (%)
(Z)/(E)b
1
2
1a
1a
1b
1b
1c
1d
1e
1f
99 (2a)
neat, 150-180 °C
66 (3a)
81 (3a)
22 (3b)
86 (3b)
94 (3c)
82 (3d)
87 (3e)
79 (3f)
87 (3g)d
96 (3h)
90 (3i)
100/0c
67/33c
100/0c
86/14c
77/23c
in DMF, 150 °C, 15 min
neat, 150-180 °C
3
99 (2b)
4
in DMF, 110 °C, 4 h
in DMF, 110 °C, 4 h
in DMF, 110 °C, 4 h
in DMF, 150 °C, 15 min
in DMF, 110 °C, 4 h
in DMF, 110 °C, 4 h
in DMF, 110 °C, 4 h
in DMF, 110 °C, 4 h
5
81 (2c)
97 (2d)
97 (2e)
97 (2f)
98 (2g)
98 (2h)
98 (2i)
6
7
8
9
1g
1h
1i
10
11
91/9e
a Isolated yield by silica gel chromatography. b Determined by 1H NMR analysis. c The geometry of the major isomers was determined
by comparison of their NMR spectra with those of (Z)-isomers prepared by the route shown in Scheme 1 (ref 4a). d With ca. 8% of 5g.e The
geometry of the major isomer was determined by comparison of its NMR spectrum with that of the (Z)-isomer reported previously (ref
10d).
TABLE 2. Palladium-Catalyzed Synthesis of
Multisubstituted Allenes 7 from Bromodienes 3a
SCHEME 4
entry
bromodiene 3
nucleophile 6 T (°C) yield of 7b (%)
1
2
(Z)- and (E)-3ac
6m
6m
6m
6m
6m
6m
6m
6n
23
23
23
23
23
23
23
40
40
23
23
40
40
23
91 (7am)
87 (7bm)
95 (7cm)
97 (7dm)
93 (7em)d
70 (7fm)e
94 (7gm)
96 (7gn)
92 (7go)
92 (7hm)
96 (7hm)
87 (7hn)
92 (7ho)
91 (7im)
(Z)- and (E)-3bc
3
(Z)- and (E)-3cc
4
3d
5
3e
6
3f
SCHEME 5
7
3g
8
3g
9
3g
6o
10
11
12
13
14
(Z)-3h
(E)-3h
(Z)-3h
(Z)-3h
3i
6m
6m
6n
6o
6m
chromatography using hexane as an eluent; however,
separation of the (Z)/(E)-isomers in 3b and 3c could not
be achieved.
a Reaction was carried out with 3 (1.0 mmol) and 6 (1.1 mmol)
in THF in the presence of the catalyst (2 mol %) generated from
[PdCl(π-allyl)]2 and dpbp. b Isolated yield by silica gel chromatog-
raphy. c As a (Z)- and (E)-mixture. d Taken from ref 4a. e The
relatively low yield could be ascribed to high volatility of the
product. The GC analysis of the crude reaction mixture showed a
nearly quantitative yield of 7fm.
The scope of the present reaction is broad, and a wide
range of substitution patterns are acceptable to the
allylsilane substrates. Allylsilanes with a terminal alk-
enyl moiety such as 1d and 1e gave bromobutadienes
with no substituents at both termini (entries 6 and 7).
This synthetic strategy could be applicable to γ,γ-disub-
stituted allylsilanes, and 1,1-disubstituted-2-bromo-1,3-
butadiene derivatives were prepared in excellent yields
(entries 8-11). Note that diene 3g was obtained with ca.
8% of an inseparable isomeric diene 5g (entry 9). When
the thermolysis of 2g was performed at higher temper-
ature (150 °C) in DMF, a mixture of 3g and 5g was
obtained in 73% yield with a ratio of 3g/5g ) 83/17.
Formation of 5g could be rationalized as thermal isomer-
ization of the initially formed 3g under the thermolysis
conditions as shown in Scheme 5.15 Indeed, 2g was
treated in DMF for a short period (ca. 20 min), and an1H
NMR analysis of the reaction mixture revealed that
conversion of 2g into 3g was ca. 40% and no 5g was
detected.
conditions identical with the previous report,4a i.e., with
2 mol % of Pd(PPh3)4 at room temperature, no reaction
was observed and the dibromoolefin was recovered in
>90% yield.16 On the other hand, under more vigorous
conditions, i.e., with (CH2dCH)MgBr using 10 mol % of
NiCl2(PPh3)2 in refluxing THF, the dibromoolefin was
completely consumed; however, the product was obtained
as a complex mixture and only a trace amount of
bromobutadienes (Z)- and (E)-3h was detected in the 1H
NMR spectrum.17
Palladium-Catalyzed Reactions of 2-Bromo-1,3-
dienes with Nucleophiles. The bromodienes 3 obtained
here are excellent substrates for the Pd-catalyzed allene
synthesis.4,5 The results of the Pd-catalyzed reaction are
summarized in Table 2 and Scheme 6. As reported
previously,4a 1-monosubstituted 2-bromo-1,3-butadienes
(3a-c) and terminally unsubstituted 3-hydrocarbyl-2-
bromo-1,3-butadienes (3d,e) reacted with a soft nucleo-
phile Na[CMe(COOMe)2] (6m) in THF in the presence
As a leaving silyl group, not only Me3Si- but PhMe2Si-
is applicable for the bromodiene synthesis (entries 8 and
11).
For preparation of 1,1-disubstituted 2-bromo-1,3-buta-
dienes, reactions of 1,1-dibromo-2-phenylpropene with a
(vinyl)metal reagent were also examined. When the
dibromoolefin was treated with (CH2dCH)ZnCl under
(16) Stoichiometric reactions of 1,1-dibromo-2-phenylpropene with
Pd(PPh3)4 were reported; see: Ma, S.; Xu, B.; Ni, B. J. Org. Chem.
2000, 65, 8532.
(17) Reaction of 1,1-dibromo-2-phenylpropene with
a Grignard
(15) (a) Frey, H. M.; Walsh, R. Chem. Rev. 1969, 69, 103. (b) Curry,
M. J.; Stevens, I. D. R. J. Chem. Soc., Perkin Trans. 1 1980, 1756.
reagent in the presence of a Ni catalyst was reported; see: Okamoto,
Y.; Yoshikawa, Y.; Hayashi, T. J. Organomet. Chem. 1989, 359, 143.
J. Org. Chem, Vol. 70, No. 10, 2005 3873

Ogasawara et al.
SCHEME 6
SCHEME 8
process, 2-bromo-1,3-butadienes, have been demonstrated
as useful synthons in many organic transformations, and
our method also provides a novel route to these bromo-
diene derivatives as well. Allylsilanes have been estab-
lished as versatile synthetic intermediates, and their
preparation methods have been well-developed. This fact,
combined with the high yield of the present process,
should enhance the synthetic usefulness of our method.
SCHEME 7
Experimental Section
of 2 mol % of a Pd catalyst generated in situ from [PdCl-
(π-allyl)]2 and dpbp18 to give the corresponding allenes
in excellent yields (Table 2, entries 1-5).
Preparation of Dibromosilylmethylcyclopropanes 2.
The yields are described in Table 1. To a suspension of
allylsilane 1 (10 mmol) and KOtBu (3.4 g, 30 mmol) in dry
hexane (20 mL) was slowly added bromoform (7.6 g, 30 mmol)
at 0 °C. The mixture was stirred for 1 h at 0 °C and an
additional 1 h at room temperature. The mixture was then
filtered through Celite, and the filtrate was washed with
saturated NaCl solution. The aqueous phase was extracted
with ether, and the combined organic layer was dried over
MgSO4. After removal of the solvent, the crude product was
purified by column chromatography on silica gel (with hexane)
to give the dibromocyclopropane 2 as colorless oil. These
compounds were >95% pure (by 1H NMR) and used for the
next step without further purification. Because of their
thermal instability, the products were characterized by NMR
measurements, and HRMS and EA analyses were not per-
The bromodiene 3a was used for the Pd-catalyzed
reaction as a mixture of the (Z)- and (E)-isomers, and
the allene 7am was obtained as the sole product in 91%
yield (entry 1). During the transformation of 3a into 7am,
the geometrical isomeric information in 3a was lost
because of the perpendicular structure of the allenic Cd
CdC moiety in 7am, and thus, the isostructural allene
was obtained from both (Z)- and (E)-3a (Scheme 7).
Similarly, 3b and 3c, which were obtained as the (Z)/
(E)-mixtures, could be used for the allene synthesis
without separating the isomers.
The 1,1-disubstituted 2-bromo-1,3-dienes 3f-h are as
reactive as the 1-monosubstituted bromodienes for the
Pd-catalyzed reaction. With these bromodienes, 1,1-
disubstituted allenes, which were not accessible by the
previous method,4a were prepared in excellent yields
(entries 6-13). The two geometrical isomers of 3h were
easily separated by silica gel chromatography, and both
(Z)- and (E)-3h displayed nearly identical reactivity
toward the Pd-catalyzed reaction with 6m (entries 10 and
11). Other soft nucleophiles, such as 6n and a N-
nucleophile 6o, are applicable for preparation of 1,1-
disubstituted allenes as well (entries 8, 9, 12, and 13).
Even persubstituted allenes could be made by the route
developed in this study. Allylsilane 1i, which possesses
a persubstituted alkenyl moiety, was converted into 1,1,3-
trisubstituted 2-bromo-1,3-butadiene 3i. Treatment of 3i
with 6m under the Pd catalysis afforded the persubsti-
tuted allene 7im in 91% yield (entry 14). The Pd-
catalyzed reaction of 3i with 0.5 equiv of dimethyl
malonate in the presence of equimolar NaH gave a
persubstituted bis-allene 8i in 89% yield (Scheme 8).
1
formed. The H and 13C{1H} NMR data of the dibromocyclo-
propanes are listed below.
trans-1,1-Dibromo-2-phenyl-3-(trimethylsilylmethyl)-
cyclopropane (2a). 1H NMR (CDCl3): δ 0.09 (s, 9H), 0.77
(dd, J ) 9.4 and 14.7 Hz, 1H), 1.31 (dd, J ) 5.3 and 14.7 Hz,
1H), 1.87 (ddd, J ) 5.3, 8.5, and 9.4 Hz, 1H), 2.38 (d, J ) 8.5
Hz, 1H), 7.19-7.28 (m, 2H), 7.29-7.32 (m, 3H). 13C{1H} NMR
(CDCl3): δ -1.3, 20.4, 32.5, 41.4, 42.8, 127.4, 128.2, 128.5,
136.5.
trans-1,1-Dibromo-2-hexyl-3-(trimethylsilylmethyl)cy-
clopropane (2b). 1H NMR (CDCl3): δ 0.11 (s, 9H), 0.61-0.68
(m, 1H), 0.90-1.08 (m, 6H), 1.34-1.59 (m, 10H). 13C{1H} NMR
(CDCl3): δ -0.8, 14.6, 20.7, 23.1, 28.7, 29.5, 32.2, 33.3, 34.3,
38.8, 42.5.
trans-1,1-Dibromo-2-cyclohexyl-3-(trimethylsilylmeth-
yl)cyclopropane (2c). 1H NMR (CDCl3): δ 0.12 (s, 9H), 0.70
(dd, J ) 7.3 and 14.9 Hz, 1H), 0.81-0.85 (m, 1H), 0.99 (dd, J
) 6.9 and 14.9 Hz, 1H), 1.09-1.31(m, 7H), 1.68-1.76 (m, 4H),
2.08-2.10 (m, 1H). 13C{1H} NMR (CDCl3): δ -0.3, 21.5, 26.4,
26.9, 27.1, 32.5, 32.9, 33.6, 42.2, 43.3 44.8.
1,1-Dibromo-2-heptyl-2-(trimethylsilylmethyl)cyclo-
1
propane (2d). H NMR (CDCl3): δ 0.06 (s, 9H), 0.82-0.93-
(m, 4H), 1.14-1.65 (m, 15H). 13C{1H} NMR (CDCl3): δ 0.0,
14.4, 22.9, 23.7, 26.6, 29.5, 29.8, 32.1, 32.7, 35.8, 38.2, 42.7.
Conclusions
1,1-Dibromo-2-phenyl-2-(trimethylsilylmethyl)cyclo-
1
propane (2e). H NMR (CDCl3): δ 0.07 (s, 9H), 1.41 (d, J )
In summary, we have developed a general and efficient
new method for the conversion of allylsilane derivatives
to functionalized allenes. Using allylsilanes with proper
substituents at proper positions, a variety of multisub-
stituted allenes can be made. The intermediates of the
14.5 Hz, 1H), 1.99 (d, J ) 7.7 Hz, 1H), 2.03 (d, J ) 14.5 Hz,
1H), 2.56 (d, J ) 7.7 Hz, 1H), 7.57-7.68 (m, 5H). 13C{1H} NMR
(CDCl3): δ -1.3, 29.5, 33.4, 37.8, 39.9, 127.3, 128.3, 128.9,
141.4.
1,1-Dibromo-2,2-dimethyl-3-[(phenyldimethylsilyl)m-
1
ethyl]cyclopropane (2f). H NMR (CDCl3): δ 0.38 (s, 3H),
0.39 (s, 3H), 0.77 (dd, J ) 7.6 and 15.1 Hz, 1H), 0.99 (dd, J )
6.7 and 15.1 Hz, 1H), 1,02 (s, 3H), 1.25 (dd, J ) 6.7 and 7.6
Hz, 1H), 1.29 (s, 3H), 7.35-7.38 (m, 3H), 7.52-7.54 (m, 2H).
(18) dpbp)2,2′-bis(diphenylphosphino)-1,1′-biphenyl.See: Ogasawara,
M.; Yoshida, K.; Hayashi, T. Organometallics 2000, 19, 1567 and
references cited therein.
3874 J. Org. Chem., Vol. 70, No. 10, 2005

Preparation of Multisubstituted Allenes from Allylsilanes
13C{1H} NMR (CDCl3): δ -2.6, -2.3, 15.1, 19.9, 27.8, 28.8,
(CDCl3): δ 14.1, 22.6, 28.3, 29.1, 29.3, 31.8, 33.5, 117.5, 118.4,
132.5, 145.5. EI-HRMS: calcd for C11H19Br 230.0670, found
230.0677.
37.2, 51.6, 128.3, 129.7, 134.0, 138.7.
1,1-Dibromo-2,2-(1,5-pentanediyl)-3-(trimethylsilylm-
3-Bromo-4-methyl-1,3-pentadiene (3f).19 1H NMR
(CDCl3): δ 1.95 (s, 3H), 2.03 (s, 3H), 5.18 (d, J ) 10.8 Hz, 1H),
5.53 (d, J ) 15.9 Hz, 1H), 6.50 (dd, J ) 10.8 and 15.9 Hz, 1H).
13C{1H} NMR (CDCl3): δ 21.1, 26.4, 117.8, 119.8, 131.6, 135.9.
EI-HRMS: calcd for C6H9Br 159.9888, found 159.9883.
2-Bromo-1,1-(1,5-pentanediyl)-1,3-butadiene (3g). 1H
NMR (CDCl3): δ 1.54 (m, 6H), 2.46-2.57 (m, 4H), 5.22 (d, J
) 10.8 Hz, 1H), 5.60 (d, J ) 15.9 Hz, 1H), 6.74 (dd, J ) 10.8
and 15.9 Hz, 1H). 13C{1H} NMR (CDCl3): δ 26.4, 27.4, 27.8,
31.9, 36.5, 117.3, 118.6, 131.1, 143.6. EI-HRMS: calcd for
C9H13Br 200.0200, found 200.0192.
1
ethyl)cyclopropane (2g). H NMR (CDCl3): δ 0.04 (s, 9H),
0.54 (dd, J ) 6.4 and 15.0 Hz, 1H), 0.64 (dd, J ) 7.8 and 15.0
Hz, 1H), 1.13 (dd, J ) 6.4 and 7.8 Hz, 1H), 1.33-1.60 (m, 10H).
13C{1H} NMR (CDCl3): δ -1.3, 14.0, 24.5, 25.0, 25.9, 30.0, 33.4,
36.9, 37.5, 50.8.
trans-1,1-Dibromo-2-methyl-2-phenyl-3-(trimethylsi-
1
lylmethyl)cyclopropane (2h). H NMR (CDCl3): δ 0.15 (s,
9H), 0.75 (dd, J ) 7.0 and 15.1 Hz, 1H), 0.88 (dd, J ) 7.4 and
15.1 Hz, 1H), 1.42 (s, 3H), 1.95 (dd, J ) 7.0 and 7.4 Hz, 1H),
7.22-7.26 (m, 3H), 7.31-7.34 (m, 2H). 13C{1H} NMR
(CDCl3): δ -1.2, 15.0, 21.9, 35.0, 37.7, 48.0, 127.0, 128.3, 128.4,
144.6.
(Z)-3-Bromo-4-phenyl-1,3-pentadiene (Z-3h). 1H NMR
(CDCl3): δ 2.34 (s, 3H), 5.08 (d, J ) 10.5 Hz, 1H), 5.56 (d, J )
15.9 Hz, 1H), 6.32 (dd, 10.5 and 15.9 Hz, 1H), 7.15-7.38 (m,
5H). 13C{1H} NMR (CDCl3): δ 21.3, 119.3, 126.5, 128.0, 128.1,
128.9, 129.5, 136.5, 141.8. EI-HRMS: calcd for C11H11Br
222.0044, found 222.0042.
1,1-Dibromo-2,2,3-trimethyl-3-[(phenyldimethylsilyl)-
methyl]cyclopropane (2i). 1H NMR (CDCl3): δ 0.41 (s, 3H),
0.42 (s, 3H), 1.16 (d, J ) 14.5 Hz, 1H), 1.17 (s, 3H), 1.20 (s,
3H), 1.24 (s, 3H), 1.25 (d, J ) 14.5 Hz, 1H), 7.22-7.36 (m,
3H), 7.53-7.56 (m, 2H). 13C{1H} NMR (CDCl3): δ -1.5, -1.5,
21.7, 21.9, 22.5, 23.1, 30.3, 32.3, 61.1, 127.8, 129.0, 133.5, 139.6.
Preparation of Bromodienes 3. The reaction conditions
and results are described in Table 1. Dibromocyclopropane 2
(4.0 mmol) was dissolved in DMF (30 mL), and the solution
was heated to 110 °C for 4 h (or 150 °C for 15 min) with
stirring. Then the solution was poured onto ice-water and the
mixture was extracted with hexane four times. The combined
hexane solution was washed with water twice and dried over
MgSO4. After removal of the solvent, the crude product was
purified by column chromatography on silica gel (with hexane)
or by vacuum-transfer to give the bromodiene 3 as colorless
oil. The bromodienes (Z)-3a,4a,14 3e,4a and 3i6c were character-
ized by comparison of their spectroscopic data with those
reported previously. The characterization data of the other
bromodienes are listed below.
1
(E)-3-Bromo-4-phenyl-1,3-pentadiene (E-3h). H NMR
(CDCl3): δ 2.24 (s, 3H), 5.39 (d, J ) 10.5 Hz, 1H), 5.74 (d, J )
15.6 Hz, 1H), 6.80 (dd, 10.5 and 15.6 Hz, 1H), 7.19-7.40 (m,
5H). 13C{1H} NMR (CDCl3): δ 22.2, 120.2, 120.3, 127.2, 127.7,
128.1, 131.8, 139.6, 144.7. EI-HRMS: calcd for C11H11Br
222.0044, found 222.0044.
1-Bromo-1-(1-cyclohexenyl)propene (5g). This com-
pound was an inseparable minor product and characterized
1
1
by H and 13C{1H} NMR only. H NMR (CDCl3): δ 1.59 (m,
4H), 1.87 (d, J ) 6.6 Hz, 3H), 2.18-2.19 (m, 2H), 2.23-2.26
(m, 2H), 5.97 (q, J ) 6.6 Hz, 1H), 6.24 (m, 1H). 13C{1H} NMR
(CDCl3): δ 17.7, 22.1, 22.8, 25.7, 27.0, 121.8, 129.2, 130.4,
134.5.
Palladium-Catalyzed Synthesis of Allenes 7. The reac-
tion was conducted according to a reported procedure.4a The
reaction conditions and results are described in Table 2. A
mixture of [PdCl(π-allyl)]2 (1.8 mg, 10 µmol/Pd), dpbp (5.7 mg,
11 mmol), and 3 (0.50 mmol) was dissolved in THF (5 mL),
and the solution was added to the nucleophile 6 (0.55 mmol)
by cannula transfer under nitrogen. The mixture was stirred
at appropriate temperature for 12 h, then filtered through a
short pad of SiO2 to remove precipitated inorganic salts. The
silica gel pad was washed with a small amount of Et2O three
times and the combined solution was evaporated to dryness
under reduced pressure. The yellow residue was chromato-
graphed on silica gel to give the allene 7. The allenes 7am
and 7em were characterized by comparison of their spectro-
scopic data with those reported previously.4a The characteriza-
tion data of the other allenic products are listed below.
Dimethyl 2-Methyl-2-(2,3-decadienyl)propan-1,3-dio-
ate (7bm). 1H NMR (CDCl3): δ 0.88 (t, J ) 6.8 Hz, 3H), 1.27-
1.40 (m, 8H), 1.44 (s, 3H), 1.92-1.98 (m, 2H), 2.50 (m, 2H),
4.90-5.00 (m, 1H), 5.04-5.11 (m, 1H). 13C{1H} NMR
(CDCl3): δ 14.0, 19.7, 22.5, 28.7, 28.7, 29.8, 31.6, 35.9, 52.37,
52.40, 53.9, 84.9, 90.9, 172.18, 172.24, 205.9. Anal. Calcd for
C16H26O4: C, 68.06; H, 9.28. Found: C, 67.77; H, 9.19.
Dimethyl 2-Methyl-2-(4-cyclohexyl-2,3-butadienyl)pro-
pan-1,3-dioate (7cm). 1H NMR (CDCl3): δ 1.04-1.32 (m, 6H),
1.44 (s, 3H), 1.61-1.73 (m, 4H), 1.90-1.95 (m, 1H), 2.51-2.63
(m, 2H), 3.72 (s, 6H), 4.92-5.00 (m, 1H), 5.04-5.09 (m, 1H).
13C{1H} NMR (CDCl3): δ 19.8, 25.9, 26.1, 32.96, 32.99, 36.2,
37.1, 52.4, 52.5, 53.8, 85.9, 96.9, 172.27, 172.31, 204.7. Anal.
Calcd for C16H24O4: C, 68.54; H, 8.63. Found: C, 68.40; H,
8.61.
(E)-2-Bromo-1-phenyl-1,3-butadiene (E-3a). 1H NMR
(CDCl3): δ 5.35 (d, J ) 10.6 Hz, 1H), 5.72 (d, J ) 16.2 Hz,
1H), 6.69 (dd, J ) 10.6 and 16.2 Hz, 1H), 7.10 (s, 1H), 7.14-
7.28 (m, 5H). 13C{1H} NMR (CDCl3): δ 122.3, 125.1, 127.8,
128.4, 128.9, 131.4, 134.5, 136.0. EI-HRMS: calcd for C10H9-
Br 207.9887, found 207.9893.
(Z/E)-3-Bromo-1,3-decadiene
(Z/E-3b).
1H
NMR
(CDCl3): δ 0.88-0.92 (m, 3H of Z/E-isomers), 1.31-1.48 (m,
8H of Z/E-isomers), 2.23 (td, J ) 6.8 and 7.9 Hz, 2H of
E-isomer), 2.32 (dt, J ) 7.1 and 7.6 Hz, 2H of Z-isomer), 5.16
(d, J ) 10.4 Hz, 1H of Z-isomer), 5.31 (d, J ) 10.6 Hz, 1H of
E-isomer), 5.54 (d, J ) 16.3 Hz, 1H of Z-isomer), 5.63 (d, J )
16.1 Hz, 1H of E-isomer), 5.99 (t, J ) 7.1 Hz, 1H of Z-isomer),
6.09 (t, J ) 7.9 Hz, 1H of E-isomer), 6.31 (dd, J ) 10.4 and
16.3 Hz, 1H of Z-isomer), 6.58 (dd, J ) 10.6 and 16.3 Hz, 1H
of E-isomer). 13C{1H} NMR for (Z)-isomer (CDCl3): δ 14.1, 22.6,
28.3, 28.9, 31.5, 31.6, 117.0, 125.8, 135.3, 135.9. 13C{1H} NMR
for (E)-isomer (CDCl3): δ 14.1, 22.7, 28.8, 29.1, 29.6, 31.6,
120.1, 122.0, 129.9, 136.3. EI-HRMS: calcd for C10H17Br
216.0513, found 216.0500.
(Z/E)-2-Bromo-1-cyclohexyl-1,3-butadiene (Z/E-3c). 1H
NMR (CDCl3): δ 1.04-1.41 (m, 6H of Z/E-isomers), 1.63-2.05
(m, 4H of Z/E-isomers), 2.45-2.63 (m, 1H of Z/E-isomers), 5.16
(d, J ) 10.2 Hz, 1H of Z-isomer), 5.30 (d, J ) 10.5 Hz, 1H of
E-isomer), 5.52 (d, J ) 16.5 Hz, 1H of Z-isomer), 5.61 (d, J )
16.2 Hz, 1H of E-isomers), 5.80 (d, J ) 8.7 Hz, 1H of Z-isomer),
5.95 (d, J ) 9.9 Hz, 1H of E-isomer), 6.28 (dd, J ) 10.2 and
16.5 Hz, 1H of Z-isomer), 6.58 (dd, J ) 10.5 and 16.2 Hz, 1H
of E-isomer). 13C{1H} NMR for (Z)-isomer (CDCl3): δ 25.5, 25.9,
31.7, 40.4, 117.1, 123.8, 135.9, 140.0. 13C{1H} NMR for (E)-
isomer (CDCl3): δ 25.6, 25.7, 32.7, 38.9, 120.0, 120.9, 130.0,
141.5. EI-HRMS: calcd for C10H15Br 214.0357, found 214.0349.
Dimethyl 2-Methyl-2-(2-heptyl-2,3-butadienyl)propan-
1,3-dioate (7dm). 1H NMR (CDCl3): δ 0.88 (t, J ) 6.6 Hz,
3H), 1.26-1.44 (m, 10H), 1.48 (s, 3H), 1.83-1.90 (m, 2H), 2.58
(t, J ) 2.7 Hz, 2H), 3.70 (s, 6H), 4.62-4.66 (m, 2H). 13C{1H}
NMR (CDCl3): δ 14.1, 19.8, 22.6, 27.4, 29.12, 29.14, 31.8, 33.3,
2-Bromo-3-heptyl-1,3-butadiene (3d). 1H NMR (CDCl3):
δ 0.88 (t, J ) 6.8 Hz, 3H), 1.27-1.34 (m, 8H), 1.41-1.47 (m,
2H), 2.31 (dt, J ) 1.6 and 7.8 Hz, 2H), 5.15 (s, 1H), 5.51 (s,
1H), 5.65 (s, 1H), 5.87 (d, J ) 1.6 Hz, 1H). 13C{1H} NMR
(19) Nilsen, N. O.; Skattebøl, L.; Baird, M. S.; Buxton, S. R.; Slowey,
P. D. Tetrahedron Lett. 1984, 25, 2887.
J. Org. Chem, Vol. 70, No. 10, 2005 3875

Ogasawara et al.
37.4, 52.4, 53.5, 76.3, 98.4, 172.5, 206.6. Anal. Calcd for
C17H28O4: C, 68.89; H, 9.52. Found: C, 68.73; H, 9.50.
Dimethyl 2-Methyl-2-(4-methyl-2,3-pentadienyl)pro-
pan-1,3-dioate (7fm). 1H NMR (CDCl3): δ 1.41 (s, 3H), 1.62
(d, J ) 2.7 Hz, 6H), 2.50 (d, J ) 7.5 Hz, 2H), 3.69 (s, 6H), 4.79
(m, 1H). 13C{1H} NMR (CDCl3): δ 19.6, 20.5, 36.1, 52.5, 53.8,
82.9, 95.1, 172.4, 203.8. Anal. Calcd for C12H18O4: C, 63.70;
H, 8.02. Found: C, 63.67; H, 8.18.
Dimethyl 2-Methyl-2-[4,4-(1,5-pentanediyl)-2,3-butadi-
enyl]propan-1,3-dioate (7gm). 1H NMR (CDCl3): δ 1.44 (s,
3H), 1.44-1.61 (m, 6H), 2.04-2.08 (m, 4H), 2.54 (d, J ) 7.5
Hz, 2H), 3.72 (s, 6H), 4.80-4.85 (m, 1H). 13C{1H} NMR
(CDCl3): δ 19.5, 26.0, 27.1, 31.4, 36.3, 52.4, 53.8, 82.7, 102.1,
172.3, 200.5. Anal. Calcd for C15H22O4: C, 67.64; H, 8.33.
Found: C, 67.80; H, 8.26.
Diethyl 2-Acetamido-2-[4,4-(1,5-pentanediyl)-2,3-buta-
dienyl]propane-1,3-dioate (7gn). 1H NMR (CDCl3): δ 1.26
(t, J ) 7.2 Hz, 6H), 1,46-1.57(m, 6H), 2.02-2.06 (m, 7H), 2.98
(d, J ) 7.5 Hz, 2H), 4.16-4.32 (m, 4H), 4.69-4.75 (m, 1H),
6.82 (br, 1H). 13C{1H} NMR (CDCl3): δ 14.0, 23.0, 25.9, 27.1,
31.4, 33.0, 62.5, 66.5, 81.6, 102.4, 167.7, 168.7, 200.6. Anal.
Calcd for C18H27NO5: C, 64.07; H, 8.07; N, 4.15. Found: C,
64.09; H, 8.26; N, 4.05.
Di-tert-butyl N-[4,4-(1,5-Pentanediyl)-2,3-butadienyl]-
iminodicarboxylate (7go). 1H NMR (CDCl3): δ 1.50 (s, 18H),
1.54-1.62 (m, 6H), 2.09 (m 4H), 4.18 (d, J ) 2.7 Hz, 2H), 5.01-
5.06 (m, 1H). 13C{1H} NMR (CDCl3): δ 26.0, 27.3, 28.1, 31.4,
45.5, 82.0, 85.9, 104.8, 152.2, 198.1. Anal. Calcd for C19H31-
NO4: C, 67.63; H, 9.26; N, 4.15. Found: C, 67.57; H, 9.20; N,
4.14.
Hz, 3H), 1.25 (t, J ) 7.2 Hz, 3H), 1.86 (s, 3H), 2.05 (d, J ) 2.7
Hz, 3H), 3.14 (d, J ) 7.5 Hz, 2H), 4.09-4.31 (m, 4H), 5.20-
5.26 (m, 1H), 6.77 (br, 1H), 7.18-7.37 (m, 5H). 13C{1H} NMR
(CDCl3): δ 13.9, 14.0, 17.0, 22.8, 32.4, 62.59, 62.63, 66.3, 86.0,
101.0, 125.7, 126.8, 128.3, 136.8, 167.5 (2C), 169.0, 206.1. Anal.
Calcd for C20H25NO5: C, 66.83; H, 7.01; N, 3.90. Found: C,
66.99; H, 7.01; N, 3.70.
Di-tert-butyl N-(4-Phenyl-2,3-pentadienyl)iminodicar-
boxylate (7ho). 1H NMR (CDCl3): δ 1.45 (s, 18H), 2.09 (d, J
) 2.7 Hz, 2H), 4.26 (d, J ) 5.7 Hz, 3H), 5.53 (qt, J ) 2.7 and
5.7 Hz, 1H), 7.15-7.41 (m, 5H). 13C{1H} NMR (CDCl3): δ 17.0,
28.0, 44.9, 82.3, 90.1, 102.8, 125.9, 126.7, 128.1, 136.7, 152.2,
204.2. Anal. Calcd for C21H29NO4: C, 70.17; H, 8.13; N, 4.15.
Found: C, 70.11; H, 8.18; N, 3.83.
Dimethyl 2-Methyl-2-(2,4-dimethyl-2,3-pentadienyl)-
1
propan-1,3-dioate (7im). H NMR (CDCl3): δ 1.46 (s, 3H),
1.60 (s, 6H), 1.61 (s, 3H), 2.56 (s, 2H), 3.70 (s, 6H). 13C{1H}
NMR (CDCl3): δ 19.5, 20.6, 20.8, 39.6, 52.4, 53.2, 91.8, 95.3,
172.5, 199.6. Anal. Calcd for C13H20O4: C, 64.98; H, 8.39.
Found: C, 65.12; H, 8.21.
Dimethyl 2,2-Bis(2,4-dimethyl-2,3-pentadienyl)propan-
1,3-dioate (8i). 1H NMR (CDCl3): δ 1.60 (s, 12H), 1.61 (s, 6H),
2.69 (s, 4H), 3.67 (s, 6H). 13C{1H} NMR (CDCl3): δ 20.8, 21.1,
35.5, 52.4, 56.7, 92.2, 95.2, 171.4, 199.8. Anal. Calcd for
C19H28O4: C, 71.22; H, 8.81. Found: C, 71.20; H, 8.87.
Acknowledgment. A part of this work was sup-
ported by a Grant-in-Aid for Scientific Research (the
Ministry of Education, Japan) and the Kurata Founda-
tion (to M.O.).
Dimethyl 2-Methyl-2-(4-phenyl-2,3-pentadienyl)propan-
1,3-dioate (7hm). 1H NMR (CDCl3): δ 1.50 (s, 3H), 2.07 (d, J
) 3.0 Hz, 3H), 2.69 (d, J ) 7.8 Hz, 2H), 3.69 (s, 6H), 5.33 (qt,
J ) 3.0 and 7.8 Hz, 1H), 7.17-7.38 (m, 5H). 13C{1H} NMR
(CDCl3): δ 17.1, 19.9, 35.8, 52.5 (2C), 53.7, 87.2, 100.6, 125.7,
126.6, 128.2, 136.8, 172.2 (2C), 205.9. Anal. Calcd for
C17H20O4: C, 70.81; H, 6.99. Found: C, 70.26; H, 7.07.
Diethyl 2-Acetamido-2-(4-phenyl-2,3-pentadienyl)pro-
Supporting Information Available: 1H- and 13C NMR
spectra for all of the new compounds. This material is available
free of charge via the Internet at http://pubs.acs.org.
1
pane-1,3-dioate (7hn). H NMR (CDCl3): δ 1.20 (t, J ) 7.2
JO050142H
3876 J. Org. Chem., Vol. 70, No. 10, 2005