Catalyzed intramolecular olefin insertion into a carbon-carbon single bond

Article abstract of DOI:10.1021/ja021062n

Intramolecular insertion of a C-C double bond into a C-C single bond was achieved by treatment of cyclobutanone bearing an o-styryl group at the 3-position with a catalytic amount of a cationic rhodium(I)-dppp complex. Initially, rhodium is inserted betwe

Full text of DOI:10.1021/ja021062n

Published on Web 10/30/2002
Catalyzed Intramolecular Olefin Insertion into a Carbon-Carbon Single Bond
Masahiro Murakami,* Tamon Itahashi, and Yoshihiko Ito
Department of Synthetic Chemistry and Biological Chemistry, Kyoto UniVersity, Yoshida, Kyoto 606-8501, Japan
Received August 7, 2002
A wide variety of synthetic transformations are currently
available for the functionalization of organic compounds. Neverthe-
less, the controlled insertion of an unsaturated organic functionality
such as a carbon-carbon double bond into a carbon-carbon single
bond would be a synthetic protocol of considerable novelty as well
as utility. Such a transformation requires a particular method for
The production of 2a can be explained by assuming the pathway
the activation of carbon-carbon single bonds, for example, by way
of oxidative addition to a transition metal (eq 1).1
pictured below (path A in eq 3). Initially, rhodium(I) is inserted
between the carbonyl carbon and the R-carbon of 1a to generate a
five-membered cyclic acylrhodium intermediate (3) with the vinyl
group coordinating to rhodium. Migratory insertion of the vinyl
group into the rhodium-carbon bond affords the bicyclic acyl-
6
rhodium intermediate (4). Subsequent reductive elimination gives
rise to 2a and regenerates the rhodium(I) catalyst.
An alternative mechanism (path B) becomes conceivable when
the new cleavage site (â-bond cleavage) discovered with the dppe
ligand (vide infra) is taken into account. Rhodium(I) cleaves the
bond between the R-carbon and the â-carbon of 1a to generate a
five-membered rhodacycle (5). Migratory insertion of the vinyl
group into the rhodium-carbon bond and subsequent reductive
elimination afford the same ketone 2a.
However, carbon-carbon single bonds are arguably one of the
least reactive functional groups especially with respect to transition
metals. Hence, catalytic reactions in which oxidative addition of
carbon-carbon single bonds is the elementary step are still difficult
2
to achieve. We recently found that the bond between the carbonyl
carbon and the R-carbon of a cyclobutanone can be catalytically
3
cleaved by a rhodium(I) complex. Here we report the rhodium-
catalyzed intramolecular insertion reaction of a carbon-carbon
double bond into a carbon-carbon single bond which occurs as
depicted in eq 1. In a single step, the insertion reaction creates a
complex bicyclo[3.2.1]octane skeleton from cyclobutanone. In
addition, novel regioselectivity was observed in the key process of
carbon-carbon bond cleavage, presumably being brought about
through the ligation of the metal by a pendant vinyl group.
Our previous studies on the activation of carbon-carbon single
3
To determine which path the reaction follows, 13C-labeled
substrate (1b) was synthesized in which a 13C nuclide was installed
at the terminal vinylic position. The reaction of 1b furnished 2b
which contained a 13C nuclide at the R-position of the carbonyl
group. This experiment established that the initial insertion of
rhodium occurred between the carbonyl carbon and the R-carbon
bonds led us initially to attempt intermolecular insertion reactions,
all of which have so far proved unsuccessful. We then envisaged
that the desired transformation can be accomplished by situating
an unsaturated organic functionality at an appropriate position within
the substrate. The key substrate, that is, cyclobutanone equipped
with an o-substituted styryl group at the 3-position (1a), was
prepared from 1,2-divinylbenzene by [2 + 2] cycloaddition with
dichloroketene and the subsequent dechlorination with zinc. When
3
of the cyclobutanone (path A), as with the previous cases.
heated at 135 °C in xylene in the presence of [Rh(nbd)(dppp)]PF
6
4
(
5 mol %) and 2,6-di(tert-butyl)-4-methylphenol (BHT, 10 mol
5
%), cyclobutanone 1a was converted into benzobicyclo[3.2.1]octan-
3-one (2a) which was isolated in 81% yield after heating for 90
min. Obviously, this complex skeleton resulted from intramolecular
insertion of the vinyl group into a carbon-carbon single bond of
the cyclobutanone, as discussed below. The present reaction
proceeded much faster than the carbon-carbon bond cleaving
reactions of cyclobutanones previously reported, which normally
Other examples of the rhodium-catalyzed intramolecular insertion
of a carbon-carbon double bond into a carbon-carbon single bond
are shown in eq 5. The reaction of a cyclobutanone having an
electron-withdrawing substituent (1c) proceeded slightly faster than
that of 1d possessing an electron-donating group.7
3
took more than one-half of a day. It is likely that intramolecular
coordination of the vinyl group to rhodium facilitates its insertion.
*
To whom correspondence should be addressed. E-mail: murakami@
sbchem.kyoto-u.ac.jp.
1
3976 J. AM. CHEM. SOC. 2002, 124, 13976-13977
9
10.1021/ja021062n CCC: $22.00 © 2002 American Chemical Society

C O MMU N I C A T I O N S
For comparison, analogous reactions of cyclobutanone 13 having
an allyl group instead of a vinyl group were studied. Only
decarbonylation took place to form diolefin or a mixture of
cyclopropane and diolefin with a catalysis of either dppe, dppp, or
dppb complex. Appropriate location of a C-C double bond in a
4
molecule or η -type coordination of a styryl unit is important for
olefin insertion (with dppp) as well as for â bond cleavage (with
dppe).
Surprisingly, decreasing the length of the tether between the two
phosphorus atoms in the bidentate phosphine ligand dppp by only
4
one carbon to dppe gave a completely different result. While the
dppp complex gave olefin insertion via R-bond cleavage, the [Rh-
(
nbd)(dppe)]PF
R,â-unsaturated ketone (9) in 51% isolated yield. No formation of
a was observed in the NMR spectrum of the crude reaction mixture
the other starting material remained unreacted due to gradual
6
-catalyzed reaction of 1a furnished the ring-opened
2
(
In summary, a new rhodium-catalyzed synthetic sequence was
developed in which a carbon-carbon double bond was inserted
into a carbon-carbon single bond. Construction of a complex
bicyclic carbon framework from a simple cyclobutanone in a single
step is noteworthy. While the full potential awaits exploration, this
new insertion process may eventually lead to a general synthetic
protocol. An additional highlight is that the reaction patterns of
cyclobutanone 1a change dramatically according to the chain length
separating two phosphorus atoms of the employed ligand. In
particular, the use of the dppe ligand found a new site selection in
the carbon-carbon bond cleavage of cyclobutanone. A bond
deterioration of the catalyst). It is likely that rhodium(I) cleaves
3
the â-bond, that is, the bond between the R sp carbon and the â
3
sp carbon of 1a, to generate the five-membered rhodacycle (7).
Rhodacycle 7 then undergoes â-hydride elimination to give 8.
Finally, reductive elimination affords 9.
3
between two sp carbon atoms is the most inert one because no
π-orbital participation is available for incipient interaction with a
metal orbital. The present example proved it promising that the
aid of a coordinating directive group steers the position of activation
even to such an inert bond.
Acknowledgment. This research was supported by a Grant-in-
Aid for Scientific Research on Priority Areas (A) “Exploitation of
Multi-Element Cyclic Molecules” from the Ministry of Education,
Culture, Sports, Science, and Technology, Japan.
When 3-phenylcyclobutanone lacking a vinyl group was sub-
jected to identical conditions, no reaction occurred, and 3-phenyl-
cyclobutanone remained unreacted. Moreover, diphenylacetylene
Supporting Information Available: Preparation of 1, spectroscopic
data, and experimental procedure for 2, 9, and 12 (PDF). This material
is available free of charge via the Internet at http://pubs.acs.org.
(
1 equiv) or ethylene (7 atm) as a coordinating additive completely
hampered the reaction of 1a. These results demonstrate that cleavage
at the â carbon-carbon bond of 1a is guided by the vinyl
substituent; it acts as a ligand bringing rhodium into the immediate
vicinity of the â carbon-carbon bond and promotes cleavage of
this otherwise unreactive bond.
References
(
1) For reviews, see: (a) Crabtree, R. H. Chem. ReV. 1985, 85, 245. (b)
Rybtchinski, B.; Milstein, D. Angew. Chem., Int. Ed. 1999, 38, 870. (c)
Murakami, M.; Ito, Y. In ActiVation of UnreactiVe Bonds and Organic
Synthesis; Murai, S., Ed.; Springer: Berlin, 1999; p 97.
4
The use of dppb as a ligand for rhodium yielded a third distinct
and exclusive reaction pathway for 1a. As was often the case with
dppb,3 1a underwent decarbonylation to furnish diolefin (12, 93%
GC yield) when treated with [Rh(nbd)(dppb)]PF . Similarly to the
6
case with dppp, rhodium initially inserted into the R C-C bond to
form 10. Expulsion of the carbonyl group was followed by
â-hydride elimination and reductive elimination, leading to 12. The
preference the dppb ligand has for expulsion of the carbonyl group
from 10 may be attributed to the wider P-Rh-P angle, which is
expected to squeeze the ligated substrate to form a rhodacycle of
a smaller ring size through decarbonylation.
b,d
(2) (a) Kaneda, K.; Azuma, H.; Wayaku, M.; Teranishi, S. Chem. Lett. 1974,
2
9
15. (b) Suggs, J. W.; Jun, C.-H. J. Chem. Soc., Chem. Commun. 1985,
2. (c) Edelbach, E. L.; Lachicotte, R. J.; Jones, W. D. J. Am. Chem. Soc.
1998, 120, 2843. (d) Liou, S.-Y.; van der Boom, M. E.; Milstein, D. Chem.
Commun. 1998, 687. (e) Jun, C.-H.; Lee, H. J. Am. Chem. Soc. 1999,
1
21, 880. (f) Jun, C.-H.; Lee, D.-Y.; Kim, Y.-H.; Lee, H. Organometallics
2001, 20, 2928. (g) Miller, J. A. Tetrahedron Lett. 2001, 42, 6991. (h)
M u¨ ller, C.; Lachicotte, R. J.; Jones, W. D. Organometallics 2002, 21,
1975.
(
3) (a) Murakami, M.; Amii, H.; Ito, Y. Nature 1994, 370, 540. (b) Murakami,
M.; Amii, H.; Shigeto, K.; Ito, Y. J. Am. Chem. Soc. 1996, 118, 8285. (c)
Murakami, M.; Takahashi, K.; Amii, H.; Ito, Y. J. Am. Chem. Soc. 1997,
1
19, 9307. (d) Murakami, M.; Itahashi, T.; Amii, H.; Takahashi, K.; Ito,
Y. J. Am. Chem. Soc. 1998, 120, 9949. (e) Murakami, M.; Tsuruta, T.;
Ito, Y. Angew. Chem., Int. Ed. 2000, 39, 2484.
(
4) nbd ) 2,5-norbornadiene, dppp ) Ph
2
PCH
2
2
CH
2
2 2 2 2
CH PPh , dppe ) Ph -
PCH CH PPh , dppb ) Ph PCH CH CH
2
2
2
2
2
2
CH
PPh .
2
(
5) 2,6-Di(tert-butyl)-4-methylphenol (BHT) was used to prevent polymeri-
zation of the styryl group. When the reaction was carried out in the absence
of BHT, the yield of 2a decreased to 15%, while 1a was consumed.
(
6) Migratory insertion into the rhodium-(acyl carbon) linkage is also
conceivable.
(
3 6 4 2
7) For promotion by o-CF C H CHdCH , see: Giovannine, R.; St u¨ demann,
T.; Dussin, G.; Knochel, P. Angew. Chem., Int. Ed. 1998, 37, 2387.
JA021062N
J. AM. CHEM. SOC.
9
VOL. 124, NO. 47, 2002 13977