Rhodium(I)-catalyzed intramolecular carbonylative [2+2+1] cycloaddition of bis(allene)s: Bicyclo[6.3.0]undecadienones and bicyclo[5.3.0]decadienones

Article abstract of DOI:10.1002/anie.200806029

(Chemical Equation Presented) No templates needed: The title reaction makes it easy to construct the bicyclo[6.3.0]undecadienone framework in high yields (see scheme). A template effect is not required to achieve this ring-closing reaction efficiently. Th

Full text of DOI:10.1002/anie.200806029

Angewandte
Chemie
DOI: 10.1002/anie.200806029
Cyclization
Rhodium(I)-Catalyzed Intramolecular Carbonylative [2+2+1]
Cycloaddition of Bis(allene)s: Bicyclo[6.3.0]undecadienones and
Bicyclo[5.3.0]decadienones
Fuyuhiko Inagaki, Syu Narita, Takuma Hasegawa, Shinji Kitagaki, and Chisato Mukai*
The [Co2(CO)8]-mediated [2+2+1] cycloaddition involving
an alkyne p bond, an alkene p bond, and carbon monoxide
(CO) is known as the Pauson–Khand reaction,[1] and the
intramolecular Pauson–Khand reaction of enynes (alkyne/
alkene derivatives) can generally be applied to the formation
of bicyclo[3.3.0]octenones and bicyclo[4.3.0]nonenones in
good to high yields. However, the application of this protocol
to the construction of larger systems, bicyclo[5.3.0]decenones,
could not be achieved except for a few specific substrates,
which have, for example, an aromatic ring as the template.[2]
The RhI-catalyzed carbonylative [2+2+1] cycloaddition[3,4] of
allenynes (alkyne/allene derivatives)[5–7] or allenenes (alkene/
allene),[8] however, has been described by us[5,8] and Brum-
mond et al.,[6] to afford the corresponding bicyclo[5.3.0]
compounds in satisfactory yields.[9] Described herein are
the preliminary results of the [{RhCl(CO)2}2]- and
[{RhCl(CO)dppp}2]-catalyzed carbonylative ring-closing
reaction of bis(allene)s to effect the preparation of the
medium-sized bicyclo[m.3.0] skeletons (m = 5, 6).[10]
Table 1, entry 2). The formation of 2b can be interpreted in
terms of the intermediacy of the initially formed 1,3-diene
derivative 2b’’ and subsequent isomerization to the
a,b-unsaturated ketone 2b. The bicyclo[4.3.0] derivative 4,
having the exo-methylene moiety, must have been obtained
through the reaction between the terminal and internal
double bonds of the two allenyl groups. In the case of the
methylene tethered mono-phenylsulfonyl derivative 1c, the
corresponding bicyclo[5.3.0] derivative 2c became the sole
isolable product in 45% yield. Neither the bicyclo[4.3.0]
derivative nor the [2+2] cycloadduct could be detected
(Table 1, entry 3). Increasing the amount of the catalyst
used led to an increase in the total yield of the [2+2+1] cyclo-
addition products (63% yield), including isomer 2c’ (Table 1,
entry 4).[12] Gratifyingly, the bis(phenylsulfonylallene) deriv-
ative 1d was shown to be a suitable substrate affording
2,6-bis(phenylsulfonyl)bicyclo[5.3.0]deca-1,7-dien-9-one (2d)
in a quantitative yield under the influence of 5 mol% of
[{RhCl(CO)dppp}2] for one hour (Table 1, entry 5). An
alternative catalyst, [{RhCl(CO)2}2], also gave the ring-
closing product 2d in 85% yield, although a longer reaction
time (6 h) was necessary (Table 1, entry 6). Increasing the
amount of [{RhCl(CO)2}2] from 5 to 10 mol% provided 2d in
a better yield and within a shorter reaction time (Table 1,
entry 7). Notably, a lower reaction temperature (808C),
compared to the cases of allenynes and allenenes which
required refluxing toluene or xylene, was sufficient to
complete this ring-closing reaction. No [2+2] cycloaddition
products could be detected under either set of reaction
conditions, presumably because of the low reaction temper-
ature (Table 1, entries 5 and 6). The malonate derivative 1e in
the presence of 5 mol% of [{RhCl(CO)dppp}2] however,
unexpectedly furnished 2e in a low yield along with the
predominant production of the [2+2] cycloaddition product
3e in 70% yield (Table 1, entry 8). Increasing the amount of
[{RhCl(CO)dppp}2] used did not improve the yield of
2e (Table 1, entry 9). A satisfactory yield (83 or 89%) of
2e was realized by using [{RhCl(CO)2}2] instead of
[{RhCl(CO)dppp}2] (Table 1, entries 10 and 11). The
nitrogen-atom-containing substrate 1 f reacted with
[{RhCl(CO)dppp}2] to afford the corresponding azabicyclo-
[5.3.0]decadienone 2 f in 98% yield (Table 1, entry 12),
whereas 2 f was formed in a low yield (44%) when treated
with [{RhCl(CO)2}2] and the [2+2] cycloaddition product 3 f
was obtained as a by-product (Table 1, entry 13). The
oxa congener 2g could also be synthesized from 1g in the
Our initial evaluation of the RhI-catalyzed carbonylative
[2+2+1] cycloaddition of a bis(allene) focused on the prep-
aration of bicyclo[5.3.0]decadienones which would require
the participation of the two allenic terminal double bonds of
compounds 1. Indeed, the reaction of 5,5-bis(methoxycar-
bonyl)-1,2,7,8-nonatetraene (1a)[11] was first submitted to
several ring-closing reaction conditions, but only an intract-
able mixture was obtained. We then turned to examining
phenylsulfonyl-substituted derivatives, which have been uti-
lized as substrates for most of our allenyne and allenene
cyclometalation reactions because of their ready availability
as well as their ability to selectively react at the terminal
double bonds.[5,8] After several reaction conditions were
screened, we found that treatment of the malonate derivative
1b with 5 mol% of [{RhCl(CO)dppp}2] in toluene at 808C
under an atmosphere of CO produced two carbonylative
[2+2+1] cycloaddition products 2b and 4, each in 15% yield,
along with the [2+2] cycloaddition product 3b (14% yield;
[*] Dr. F. Inagaki, S. Narita, T. Hasegawa, Dr. S. Kitagaki,
Prof. Dr. C. Mukai
Division of Pharmaceutical Sciences
Graduate School of Natural Science and Technology
Kanazawa University, Kakuma-machi, Kanazawa 920-1192 (Japan)
Fax : (+81)76-234-4410
E-mail: cmukai@kenroku.kanazawa-u.ac.jp
Homepage:
http://www.p.kanazawa-u.ac.jp/~yakuzou/indexen.html
presence of [{RhCl(CO)dppp}2] in
(Table 1, entry 14). Again, [{RhCl(CO)2}2] provided 2g in a
a satisfactory yield
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.200806029.
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Table 1: Rhodium(I)-catalyzed synthesis of bicyclo[5.3.0] compounds by a carbonylative [2+2+1] cycloaddition of bis(allene)s.[a]
Entry
1
Bis(allene)
RhI catalyst
t [h]
Products (yield)[b]
1a (Z=CO2Me)
[{RhCl(CO)dppp}2]
11
complex mixture
2
1b (Z=CO2Me)
[{RhCl(CO)dppp}2]
20
2b (15%)
4 (15%, d.r. 2:1)
3b (14%)
3
4
1c
1c
[{RhCl(CO)dppp}2]
[{RhCl(CO)dppp}2][c]
21
23
2c (45%)
2c (42%)
2c’ (trace)
2c’ (21%)
5
6
7
1d
1d
1d
[{RhCl(CO)dppp}2]
[{RhCl(CO)2}2]
1
6
3
2d (quant.)
2d (85%)
2d (93%)
[{RhCl(CO)2}2][c]
8
9
10
11
1e (Z=CO2Me)
1e (Z=CO2Me)
1e (Z=CO2Me)
1e (Z=CO2Me)
[{RhCl(CO)dppp}2]
[{RhCl(CO)dppp}2][c]
[{RhCl(CO)2}2]
2
2
1
1
2e (20%)
2e (31%)
2e (83%)
2e (89%)
3e (70%)
3e (65%)
3e (16%)
3e (7%)
[{RhCl(CO)2}2][c]
12
13
1 f
1 f
[{RhCl(CO)dppp}2]
[{RhCl(CO)2}2]
1
3
2 f (98%)
2 f (44%)
3 f (–)
3 f (34%)
14
15
16
1g
1g
1g
[{RhCl(CO)dppp}2]
[{RhCl(CO)2}2]
0.5
20
4
2g (92%)
2g (28%)
2g (54%)
[{RhCl(CO)2}2][c]
[a] Reaction conditions: A solution of bis(allene) 1 (0.1 mmol) and RhI catalyst (5 mol%) in toluene (1 mL) was stirred at 808C under CO atmosphere.
[b] Yields of isolated products. [c] Used 10 mol% of the catalyst. dppp=1,3-bis(diphenylphosphino)propane. Ts=p-toluenesulfonyl.
rather low yield (Table 1, entries 15 and 16). Therefore the
results in Table 1 indicate that [{RhCl(CO)dppp}2] is superior
to [{RhCl(CO)2}2] in the carbonylative [2+2+1] cycloaddition
of the bis(allene) derivatives 1, except for the malonate
derivative 1e (Table 1, entries 8–11).
The results in Table 1 imply that the introduction of two
phenylsulfonyl groups on both allenyl functionalities makes
the intramolecular carbonylative [2+2+1] cycloaddition
between the terminal double bonds of the two allenyl
groups extremely smooth. The bulky phenylsulfonyl groups
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Table 2: Rhodium(I)-catalyzed synthesis of bicyclo[6.3.0] compounds by
a carbonylative [2+2+1] cycloaddition of bis(allene)s.[a]
might not only suppress the cyclometalation between the two
internal double bonds[11d] or between a terminal and a internal
double bond of two allenyl groups,[11c,f,g] but might also orient
the two terminal double bonds of the allenyl moieties such
that they can react. An unexpectedly easy formation of the
bicyclo[5.3.0]decadienone framework from bis(allene)s, par-
ticularly from bis(phenylsulfonylallene) derivatives, under
mild reaction conditions (5 mol% of [{RhCl(CO)dppp}2],
1 atm CO, toluene 808C, 1 h) encouraged us to apply this new
method to the construction of the bicyclo[6.3.0] skeleton. The
preparation of a bicyclo[6.3.0] ring system based on the
Pauson–Khand-type [2+2+1] cycloaddition was previously
reported by us, in which allenynes were used as substrates and
a template effect was necessary to attain high yields.[5e]
The exposure of the 3,8-bis(phenylsulfonyl)-1,2,8,9-deca-
tetraene (5a) to the standard ring-closing conditions (5 mol%
of [{RhCl(CO)dppp}2], 1 atm CO, 808C in toluene) for three
hours afforded the bicyclo[6.3.0]undecadienone derivative 6a
in 70% yield together with its isomer 6a’ in 23% yield
(Table 2, entry 1). Interconversion between 6a and 6a’ could
not be observed under the standard reaction conditions.
Therefore, the production of these two eight-membered ring
products could be rationalized by having the common
intermediate 7a; 7a could undergo a 1,3-hydrogen shift
(Ha’) to provide 6a, or a 1,5-hydrogen shift (Hb)[13] to give 6a’
(Scheme 1). Under similar conditions, the malonate deriva-
Entry Bis(allene)
t [h] Products (yield)[b]
1
3
2
3
4
5
1
1
5
22
18
6[c]
[a] Reaction conditions: A solution of bis(allene) 5 (0.1 mmol) and
[{RhCl(CO)dppp}2] (5 mol%) in toluene (1 mL) was stirred at 808C
under CO atmosphere. [b] Yields of isolated products. [c] Used 10 mol%
of the catalyst.
Scheme 1. Hydrogen shift within intermediate 7.
submitted to the standard reaction conditions to give the
carbonylative product 10 in 17% yield along with the tetraene
derivative 11 (34% yield); 11 may have arisen from a thermal
[3,3]-sigmatropic rearrangement of the starting material
(Scheme 2).[14] The mono-phenylsulfonyl substrate 12
afforded the desired product 13 in 67% yield. These results
are in good agreement with the prediction based on the
aforementioned results in Table 1. Upon treatment with
5 mol% [{RhCl(CO)dppp}2] in toluene under an atmosphere
of CO, bis(phenylsulfonylallene) derivative 14 produced 15 in
a quantitative yield as expected.
The sulfonyl group is known to be easily transformed into
various functional groups.[15] For example, a phenylsulfonyl
group can be regarded as a surrogate for a hydrogen atom,
and can be easily converted into a hydrogen atom by
conventional means. In fact, we examined the selective
desulfonylation of one of the two phenylsulfonyl groups of
the [2+2+1] cycloaddition products (Scheme 3). The removal
of a vinylic sulfone of 2e was realized in a highly selective
manner by using of two equivalents of tributyltin hydride in
the presence of AIBN[16] and the subsequent acidic workup.
Exposure of 2e to an excess of tributyltin hydride led to the
desulfonylation of both vinylic and allylic positions.
tive 5b afforded a mixture of 6b and 6b’ in 75% yield in a
ratio of 1:6 (Table 2, entry 2). Interestingly, the carbonylative
[2+2+1] cycloaddition of the nitrogen congener 5c and the
oxygen congener 5d led to the formation of the eight-
membered ring products 6c (87% yield) and 6d (86% yield),
respectively, through an exclusive 1,3-hydrogen (Ha) shift on
the side nearest to the heteroatom of 7c and d (Table 2,
entries 3 and 4). In the case of the diaza derivative 5e, the
desired carbonylative [2+2+1] cycloaddition product 6e was
formed in 27% yield as a minor product after a prolonged
reaction time. Instead, the corresponding [2+2] cycloaddition
product 8e was obtained as a major product (Table 2,
entry 5). The data in entry 6 of Table 2 indicate a significant
improvement in the yield of 6e by using 10 mol% of the
catalyst. Thus, it might be concluded that the carbonylative
[2+2+1] cycloaddition reaction of bis(allene) derivatives can
consistently and efficiently be applied to the preparation
of
both
bicyclo[5.3.0]decadienone
and
bicyclo-
[6.3.0]undecadienone skeletons.
To extend the scope of this method, we examined some
bis(allene)s that would lead to bicyclo[4.3.0]nonadienone
derivatives. The bis(allene) 9, prepared from l-tartrate, was
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Scheme 2. Formation of bicyclo[4.3.0]nonadienones by rhodium(I)-cat-
alyzed carbonylative [2+2+1] cycloaddition of bis(phenylsulfonylallene)
derivatives 9, 12, and 14.
Scheme 3. Desulfonylation of 2e. AIBN=2,2’-azobis(isobutyronitrile).
In summary, we developed a novel [{RhCl(CO)dppp}2]-
catalyzed intramolecular [2+2+1] cycloaddition of bis(phe-
nylsulfonylallene) derivatives under mild conditions leading
to the facile formation of the 2,7-bis(phenylsulfonyl)bicyclo-
[6.3.0]undecadien-10-one framework, in which the terminal
double bonds of both allenyl moieties exclusively served as
the two p components. This method is superior to that
previously reported, which took advantage of the carbon-
ylative [2+2+1] cycloaddition of allenynes possessing a
suitable template functionality. The newly developed
method was also shown to be applicable to the construction
of 2,6-bis(phenylsulfonyl)bicyclo[5.3.0]decadien-9-one and
2,5-bis(phenylsulfonyl)bicyclo[4.3.0]nonadien-8-one skele-
tons in high yields. We have demonstrated the usefulness of
a bis(allene) functionality in the carbonylative [2+2+1] cyclo-
addition reaction. The additional scope and limitations of this
method, as well as application to the synthesis of natural
products are now being investigated.
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[10] During these course of these studies, the construction of
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this paper.
Received: December 11, 2008
Published online: February 6, 2009
Keywords: allenes · bicyclic compounds · cycloaddition ·
[11] Compound 1a is a typical substrate for some reactions of 1,5-
bis(allene)s developed to date. See: a) S.-K. Kang, T.-G. Baik,
.
rhodium · sulfur
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