Rhodium(I)-catalyzed cycloisomerization of allene-allenylcyclopropanes

Article abstract of DOI:10.1002/ejoc.201403535

The Rh^I-catalyzed intramolecular [5+2-2]-type cycloisomerization of allene-allenylcyclopropanes was developed. In this reaction, ethylene was liberated from the cyclopropane ring to afford the 1,5,6,7-tetrahydroazulene skeletons.

Full text of DOI:10.1002/ejoc.201403535

SHORT COMMUNICATION
DOI: 10.1002/ejoc.201403535
Rhodium(I)-Catalyzed Cycloisomerization of Allene–Allenylcyclopropanes
[a]
[a]
[a]
[a]
Takamasa Kawamura, Yasuaki Kawaguchi, Katsuya Sugikubo, Fuyuhiko Inagaki,
and Chisato Mukai*[
a]
Keywords: Allenes / Small ring systems / Rhodium / Cycloisomerization / Cycloaddition
I
The Rh -catalyzed intramolecular [5+2–2]-type cycloisomer-
ization of allene–allenylcyclopropanes was developed. In this
reaction, ethylene was liberated from the cyclopropane ring
to afford the 1,5,6,7-tetrahydroazulene skeletons.
diene derivatives 4 (Scheme 1).[13] The allyl group of 3
would have initially isomerized into the internal double
bond and took part in the ring-closing process. On the basis
of these results, our next endeavor focused on the intramo-
lecular reaction between allenylcyclopropane and allene
moieties to compare their reactivities with those of the alk-
yne and alkene π components. This paper describes the un-
Introduction
Cyclopropane is one of the most useful and powerful C
building blocks in organic reactions owing to its inherent
3
[
1]
–
1 [2]
high strain energy (27.5 kcalmol ). Several types of tran-
sition-metal-catalyzed ring cleavages of cyclopropane have
already been recorded, and they have been exemplified by
[
3–5]
[6]
[7]
[8]
[9]
[
[
5+2],
3+2+2],
[5+2+1],
[5+1+2+1],
[3+2],
[3+2+1],
precedented behavior of cyclopropane acting as a C -build-
1
[
10]
and [3+3+1][11] cycloadditions. Recent efforts
ing block accompanied by liberation of ethylene. Thus, a
new type of ring construction mode ([5+2–2]-type ring clo-
sure) could be developed by incorporation of cyclopropane
into five-membered carbocycles.
I
from our laboratory disclosed that the Rh -catalyzed intra-
molecular [5+2] cycloaddition of alkyne–allene substrates
possessing a cyclopropane moiety efficiently produced bicy-
clo[5.4.0]undecatrienes 2 (n = 0) and bicyclo[5.5.0]dodeca-
[
12]
trienes 2 (n = 1). Exchange of the reactive alkyne part of
by an alkene group (i.e., compound 3) significantly
1
Results and Discussion
changed the reaction pathway, which led to the stereoselec-
tive construction of unexpected bicyclo[4.3.0]nona-1(9),2-
The preliminary examination was initiated by using
allene–allenylcyclopropane 5a possessing phenysulfonyl
groups on both of the two allenyl moieties. Treatment of 5a
with [RhCl(CO)dppp] [10 mol-%, dppp = 1,3-bis(diphenyl-
2
phosphino)propane], which was effective for the [5+2] cy-
cloaddition of alkyne–allenylcyclopropane 1, in toluene at
80 °C for 1 h produced 1,5,6,7-tetrahydroazulene derivative
6
a in 41% yield along with cyclopentenylidene derivative 7a
[
14,15]
(42% yield, Scheme 2).
Bicyclic products 2 and 4,
which were predicted on the basis of previous experiments,
were never isolated. The formation of 7a could be easily
interpreted by a plausible rhodacyclohexenylidene interme-
diate, followed by a reductive elimination process (see
above). The reaction mechanism for the construction of bi-
cyclo[5.3.0]decatriene skeleton 6a is not straightforwardly
understood. The two-carbon unit of 5a was clearly lost and
I
Scheme 1. Rh -catalyzed cyclization of allenylcyclopropane mul- some unprecedented stepwise mechanism should have oc-
tiple bonds.
curred during the formation of 6a. A suitable catalyst for
the conversion of 5a into 6a was screened by using
[
a] Division of Pharmaceutical Sciences, Graduate School of
[
RhCl(CO)dppm] , [RhCl(CO)dppe] , [RhCl(CO)dppb] ,
2
2
2
Medical Sciences, Kanazawa University,
[
16]
[16]
Kakuma-machi, Kanazawa 920-1192, Japan
E-mail: mukai@p.kanazawa-u.ac.jp
http://www.p.kanazawa-u.ac.jp/~yakuzou/indexen.html
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201403535.
[Rh(CO)(dppp)
]Cl,
2
[Rh(dppp)
2
]Cl,
[RhCl(CO)
2
] ,
2
RhCl(PPh ) , and trans-RhCl(CO)(PPh ) , but all of them
3
3
3 2
were less effective and furnished poor results [dppm = 1,1-
bis(diphenylphosphino)methane, dppe = 1,2-bis(diphenyl-
Eur. J. Org. Chem. 2015, 719–722
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
719

T. Kawamura, Y. Kawaguchi, K. Sugikubo, F. Inagaki, C. Mukai
SHORT COMMUNICATION
I
phosphino)ethane, dppb = 1,4-bis(diphenylphosphino)- Table 1. Rh -catalyzed cyclization of allene–allenylcyclopropanes
b–l.[
a]
5
butane]. Changing the solvent [dioxane, 1,2-dichloroethane
DCE), DMF, CH CN, iPrOH] and/or reaction tempera-
(
3
ture (25 °C to reflux) also did not give better results.
I
Scheme 2. Rh -catalyzed cyclization of allene–allenylcyclopropane
5a.
Several other bis(phenylsulfonyl) substrates were exposed
to the standard conditions {10 mol-% [RhCl(CO)dppp] in
2
toluene at 80 °C}. These results are summarized in Table 1.
Treatment of the ortho-tolylsulfonyl (oTs) derivative 5b with
[
RhCl(CO)dppp] afforded desired bicyclo[5.3.0] product 6b
2
in 28% yield together with 7b in 31% yield (Table 1, en-
try 1). The reaction of para-tolyl (pTol) and pMeOC H4
6
substrates 5c and 5d provided results similar to those ob-
tained with 5b (Table 1, entries 2 and 3). In the case of
pClC H derivative 5e, bicyclo[5.3.0] product 6e was ob-
6
4
tained in poor yield together with cyclopentenylidene prod-
uct 7e (54% yield; Table 1, entry 4). Bulky mesityl (Mes)
derivative 5f produced bicyclic product 6f in moderate yield
(45% yield; Table 1, entry 5). Aliphatic sulfonyl derivatives
5g and 5h provided desired products 6g and 6h, but their
yields were rather low (Table 1, entries 6 and 7). Thus, the
consistent formation of the bicyclo[5.3.0]decatriene skeleton
from the carbon-tethered bis(phenylsulfonyl) substrates was
achieved in low to moderate yields. The diethylphosphonate
group on the allenylcyclopropane moiety was found to
work in a manner similar to that of the sulfonyl function-
ality to furnish 6i in 30% yield (Table 1, entry 8). Applica-
I
tion of the Rh -catalyzed [5+2–2]-type cycloaddition for the
construction of the oxabicyclo[5.3.0] ring systems as well as [a] Reactions were performed by using [RhCl(CO)dppp]
2
(10 mol-
%
) in toluene at 80 °C. [b] Chemical yields were calculated on the
azabicyclo[5.3.0] ring systems was next investigated. Ether
derivative 5j was exposed to conditions similar to those
used for simple carbon tether derivatives 5a–i, and desired
oxabicyclo[5.3.0]decatriene derivative 6j was obtained in
1
basis of H NMR spectroscopy. [c] The [5+2] product was formed
in 13% yield.
3
9% yield along with cyclopentenylidene derivative 7j (28% this assumption, a deuterium labeling experiment was per-
yield; Table 1, entry 9). The reaction of N-tosylamide deriv- formed (Scheme 3). Exposure of tetradeuterated substrate
ative 5k also provided corresponding azabicyclo[5.3.0] de- [D ]5j to [RhCl(CO)dppp] in toluene at 80 °C produced
rivative 6k in 19% yield. The major product, however, be- bicyclo[5.3.0] derivative 6j in 37% yield along with deuter-
]7j in 27% yield.
4
2
came [2+2] cycloaddition product 8k, which was obtained ated cyclopentenylidene derivative [D
4
in 49% yield alongside cyclopentenylidene derivative 7k in Deuterated 6j was not detected, whereas 7j possessing the
2
1% yield (Table 1, entry 10).[
17]
N-Nosylated (Ns) sub- tetradeuterated cyclopentenylidene framework was exclu-
strate 5l behaved similarly to 5k to furnish three products:
bicyclo[5.3.0]decatriene 6l, cyclopentenylidene 7l, and bicy-
clo[5.2.0] derivative 8l (Table 1, entry 11).
It is postulated that the C H component must have been
2
4
lost during the conversion of 5 into tetrahydroazulene de-
rivatives 6. We tentatively assumed that the collapse of the
cyclopropane ring into ethylene and a C species occurred
1
and the thus-formed C unit would take part in the ring
formation reaction. To obtain some information to prove Scheme 3. Rh -catalyzed cyclization of deuterated substrate [D
1
I
4
]5j.
7
20 Eur. J. Org. Chem. 2015, 719–722
www.eurjoc.org
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

I
Rh -Catalyzed Cycloisomerization of Allene–Allenylcyclopropanes
sively formed. These results provided fairly informative
clues for understanding the reaction mechanism.
On the basis of the deuteration experiment, the following
plausible reaction mechanism might be proposed. Relief of
the high strain energy of the cyclopropane ring of substrate
5
would result in a fast reaction with the Rh catalyst to
form vinylidene π–allyl complex A (Scheme 4). Intermediate
A could be in equilibrium between rhodacyclobutane B
and/or rhodacyclohexenylidene BЈ. Intermediate B would
then liberate ethylene, which would result in the formation
[
18]
of rhodium carbenoid species C.
This could then un-
dergo a 6π-electrocyclic type ring closure[
19]
to afford
rhodabicyclo[5.4.0] intermediate D. Reductive elimination
of D would finally lead to desired tetrahydroazulene deriva-
tive 6. The production of cyclopentenylidene derivative 7
can be rationalized by the mechanism that involves interme-
diate BЈ followed by reductive elimination.
I
Scheme 5. Rh -catalyzed miscellaneous reactions of allene–allenyl-
cyclopropanes.
It is too early to conclude definitively, but judging from
the results described in Table 1 and Scheme 5, it might ten-
tatively be stated that the ring-closing pattern of allene–
allenylcyclopropane 5 clearly depends on the electronic
properties of both allenyl functionalities. The formation of
bicyclo[5.3.0]deca-1,6,8-triene skeleton 6 requires both elec-
tron-deficient groups on both allenyl groups, whereas bicy-
clo[5.5.0] derivative 8 could be produced if starting sub-
strate 5 has an alkyl substituent on its allenylcyclopropane
moiety.
Conclusions
I
Scheme 4. Plausible mechanism for the Rh -catalyzed cyclization
of allene–allenylcyclopropane substrates 5.
I
We found that the Rh -catalyzed intramolecular [5+2–2]-
type cycloisomerization of allene–allenylcyclopropane fur-
nished bicyclo[5.3.0]deca-1,6,8-triene skeletons; this was ac-
companied by the liberation of ethylene from the cyclo-
propane ring. To the best of our knowledge, this is the first
I
We next examined the Rh -catalyzed cyclization of al-
lene–allenylcyclopropanes possessing electron-donating
groups on the allene moiety. Upon exposure to the standard
conditions, 5m with a methyl group on the allenylcyclo-
propane produced bicyclo[5.5.0] derivative 8m in 60% yield
example in which the cyclopropane ring is used as a C1
building block. This novel transformation was significantly
affected by the properties of the substituents on both of the
two allenyl moieties. Details of the reaction mechanism are
still unclear. Methods to improve the chemical yields and
elucidation of the mechanism are currently under investiga-
tion.
(
Scheme 5). The corresponding tetrahydroazulene com-
pound, such as 6, was not obtained at all. Similarly, the
selective production of 8n (52%) from butyl derivative 5n
was observed. The formation of 8m and 8n could be inter-
preted in line with the plausible mechanism proposed for
the conversion of 1 into 2. Substrate 5o, having the two Supporting Information (see footnote on the first page of this arti-
substituents reversed on the allenyl moieties of 5m, no cle): Experimental procedures, characterization data, and spectro-
scopic data.
longer produced any bicyclic derivatives. Cyclopentenylid-
ene derivative 7o was instead isolated in 70% yield as the
sole isolatable product. N-Tosylamide derivative 5q with
two methyl groups on both of the two allene groups pro-
Acknowledgments
vided [5+2] product 8q in 31% yield, although correspond-
ing carbon-tethered analogue 5p gave an intractable mix- Education, Culture, Sports, Science, and Technology (Japan)
The authors are grateful for financial support by the Ministry of
ture.
through a Grant-in-Aid for Scientific Research.
Eur. J. Org. Chem. 2015, 719–722
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
721

T. Kawamura, Y. Kawaguchi, K. Sugikubo, F. Inagaki, C. Mukai
SHORT COMMUNICATION
[
8] a) L. Jiao, S. Ye, Z.-X. Yu, J. Am. Chem. Soc. 2008, 130, 7178–
7179; b) L. Jiao, M. Lin, Z.-X. Yu, Chem. Commun. 2010, 46,
1059–1061; c) T. Tamaki, M. Ohashi, S. Ogoshi, Angew. Chem.
Int. Ed. 2011, 50, 12067–12070; Angew. Chem. 2011, 123,
12273–12276.
[
1] For reviews, see: a) O. G. Kulinkovich, Chem. Rev. 2003, 103,
2597–2632; b) M. Rubina, V. Gevorgyan, Tetrahedron 2004, 60,
3129–3159; c) M. Yu, B. L. Pagenkopf, Tetrahedron 2005, 61,
321–347; d) M. Rubin, M. Rubina, V. Gevorgyan, Chem. Rev.
2007, 107, 3117–3179; e) C. A. Carson, M. A. Kerr, Chem. Soc.
[9] Y. Koga, K. Narasaka, Chem. Lett. 1999, 28, 705–706.
Rev. 2009, 38, 3051–3060; f) K. E. O. Ylijoki, J. M. Stryker,
Chem. Rev. 2013, 113, 2244–2266.
[
10] P. A. Evans, P. A. Inglesby, J. Am. Chem. Soc. 2008, 130,
2838–12839.
1
[
[
2] J. W. Knowlton, F. D. Rossini, J. Res. Natl. Bur. Stand. 1949,
[
11] S. Y. Kim, S. I. Lee, S. Y. Choi, Y. K. Chung, Angew. Chem.
Int. Ed. 2008, 47, 4914–4917; Angew. Chem. 2008, 120, 4992–
43, 113–115.
3] a) P. A. Wender, H. Takahashi, B. Witulski, J. Am. Chem. Soc.
995, 117, 4720–4721; b) P. A. Wender, C. O. Husfeld, E. Lang-
4995.
1
[12] F. Inagaki, K. Sugikubo, Y. Miyashita, C. Mukai, Angew.
kopf, J. A. Love, J. Am. Chem. Soc. 1998, 120, 1940–1941; c)
P. A. Wender, D. Sperandio, J. Org. Chem. 1998, 63, 4164–4165;
d) P. A. Wender, C. O. Husfeld, E. Langkopf, J. A. Love, N.
Pleuss, Tetrahedron 1998, 54, 7203–7220; e) P. A. Wender, A. J.
Dyckman, C. O. Husfeld, D. Kadereit, J. A. Love, H. Rieck, J.
Am. Chem. Soc. 1999, 121, 10442–10443; f) P. A. Wender, A. J.
Dyckman, Org. Lett. 1999, 1, 2089–2092; g) P. A. Wender, F. C.
Bi, M. A. Brodney, F. Gosselin, Org. Lett. 2001, 3, 2105–2108;
h) P. A. Wender, T. J. Williams, Angew. Chem. Int. Ed. 2002,
Chem. Int. Ed. 2010, 49, 2206–2210; Angew. Chem. 2010, 122,
2252–2256.
[13] K. Sugikubo, F. Omachi, Y. Miyanaga, F. Inagaki, C. Matsum-
oto, C. Mukai, Angew. Chem. Int. Ed. 2013, 52, 11369–11372;
Angew. Chem. 2013, 125, 11579–11582.
I
[14] Similar cyclopentenylidene products were observed in the Rh -
catalyzed cyclization of alkyne– and alkene–allenylcyclo-
propanes, see ref.[
10,11]
41, 4550–4553; Angew. Chem. 2002, 114, 4732–4735.
[15] M. Hayashi, T. Ohmatsu, Y.-P. Meng, K. Saigo, Angew. Chem.
Int. Ed. 1998, 37, 837–839; Angew. Chem. 1998, 110, 877–879.
[16] a) A. R. Sanger, J. Chem. Soc., Dalton Trans. 1977, 120–129;
b) B. R. James, D. Mahajan, Can. J. Chem. 1979, 57, 180–187;
c) G. La Monica, C. Monti, S. Cenini, J. Mol. Catal. 1983, 18,
93–98.
[17] Similar [2+2] cycloaddition of bis(allene)s was reported, see: a)
F. Inagaki, S. Narita, T. Hasegawa, S. Kitagaki, C. Mukai, An-
gew. Chem. Int. Ed. 2009, 48, 2007–2011; Angew. Chem. 2009,
121, 2041–2045; b) T. Kawamura, F. Inagaki, S. Narita, Y. Tak-
ahashi, S. Hirata, S. Kitagaki, C. Mukai, Chem. Eur. J. 2010,
16, 5173–5183.
[
4] For asymmetric versions of the rhodium(I)-catalyzed cycload-
dition of vinylcyclopropanes with multiple bonds, see: a) P. A.
Wender, L. O. Haustedt, J. Lim, J. A. Love, T. J. Williams, J.-Y.
Yoon, J. Am. Chem. Soc. 2006, 128, 6302–6303; b) R. Shintani,
H. Nakatsu, K. Takatsu, T. Hayashi, Chem. Eur. J. 2009, 15,
8
692–8694; for some related [5+2] cycloaddition reactions, see:
c) X.-Z. Shu, S. Huang, D. Shu, I. A. Guzei, W. Tang, Angew.
Chem. Int. Ed. 2011, 50, 8153–8156; Angew. Chem. 2011, 123,
8303–8306; d) X.-Z. Shu, X. Li, D. Shu, S. Huang, C. M.
Schienebeck, X. Zhou, P. J. Robichaux, W. Tang, J. Am. Chem.
Soc. 2012, 134, 5211–5221.
[
5] For [5+2] cycloaddition of allene–vinylcyclopropanes, see: a)
P. A. Wender, F. Glorius, C. O. Husfeld, E. Langkopf, J. A.
Love, J. Am. Chem. Soc. 1999, 121, 5348–5349; b) P. A.
Wender, M. Fuji, C. O. Husfeld, J. A. Love, Org. Lett. 1999, 1,
[18] a) M. A. A. Walczak, P. Wipf, J. Am. Chem. Soc. 2008, 130,
6924–6925; b) J. Cid, J. J. Carbó, E. Fernández, Chem. Eur. J.
2012, 18, 1512–1521; c) Y. Dang, S. Qu, Z.-X. Wang, X. Wang,
Organometallics 2013, 32, 2804–2813.
1
2
37–139; c) P. A. Wender, L. Zhang, Org. Lett. 2000, 2, 2323– [19] a) J. Barluenga, S. López, J. Flórez, Angew. Chem. Int. Ed.
326.
2003, 42, 231–233; Angew. Chem. 2003, 115, 241–243; b) J. Bar-
luenga, R. Vincente, P. Barrio, L. A. López, M. Tomás, J. Am.
Chem. Soc. 2004, 126, 5974–5975; c) Y. Lian, W. D. Wulff, J.
Am. Chem. Soc. 2005, 127, 17162–17163.
[
6] a) P. A. Wender, G. G. Gamber, R. D. Hubbard, L. Zhang, J.
Am. Chem. Soc. 2002, 124, 2876–2877; b) Y. Wang, J. Wang, J.
Su, F. Huang, L. Jiao, Y. Liang, D. Yang, S. Zhang, P. A.
Wender, Z.-X. Yu, J. Am. Chem. Soc. 2007, 129, 10060–10061.
7] P. A. Wender, G. G. Gamber, R. D. Hubbard, S. M. Pham, L.
Zhang, J. Am. Chem. Soc. 2005, 127, 2836–2837.
Received: November 26, 2014
Published Online: December 22, 2014
[
722
www.eurjoc.org
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2015, 719–722