Divergent syntheses of fused β-naphthol and indene scaffolds by rhodium-catalyzed direct and decarbonylative alkyne-benzocyclobutenone couplings

Article abstract of DOI:10.1002/anie.201310100

A tunable rhodium-catalyzed intramolecular alkyne insertion reaction proceeding through the C-C cleavage of benzocyclobutenones is described. Selective formation of either the direct or decarbonylative insertion product can be controlled by using different catalytic systems. A variety of fused β-naphthol and indene scaffolds were obtained in good yields with high functional group tolerance. This work illustrates a divergent approach to synthesize fused-ring systems by C-C activation/functionalization. Cat. in control: A tunable rhodium-catalyzed intramolecular alkyne insertion reaction proceeding through C-C cleavage of benzocyclobutenones is described. Selective formation of either the direct or decarbonylative insertion product can be controlled by using different catalytic systems. A variety of fused β-naphthol and indene scaffolds were obtained in good yields with high functional-group tolerance. Copyright

Full text of DOI:10.1002/anie.201310100

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DOI: 10.1002/anie.201310100
À
C C Activation Very Important Paper
Divergent Syntheses of Fused b-Naphthol and Indene Scaffolds by
Rhodium-Catalyzed Direct and Decarbonylative
Alkyne–Benzocyclobutenone Couplings**
Peng-hao Chen, Tao Xu, and Guangbin Dong*
Abstract: A tunable rhodium-catalyzed intramolecular alkyne
[X + Y-1]-type coupling by extruding CO from the substrate
to give the fused ring D (Scheme 1), a process which remains
largely elusive.[8,9] Herein, we describe our efforts in devel-
oping a divergent approach to realize both regular and
decarbonylative “cut and sew” transformations through
rhodium-catalyzed intramolecular couplings between benzo-
cyclobutenones[10] and alkynes (Scheme 2B). The resulting b-
naphthol and indene fused-ring products provided by this
approach are useful synthetic building blocks,[11] and have also
been found in a number of biologically important molecules
(Figure 1).
À
insertion reaction proceeding through the C C cleavage of
benzocyclobutenones is described. Selective formation of
either the direct or decarbonylative insertion product can be
controlled by using different catalytic systems. A variety of
fused b-naphthol and indene scaffolds were obtained in good
yields with high functional group tolerance. This work
illustrates a divergent approach to synthesize fused-ring
À
systems by C C activation/functionalization.
À
T
ransition-metal-catalyzed C C activation/functionalization
À
offers unique opportunities to develop novel transformations,
because it allows reorganization of bond connections leading
to novel molecular structures with high complexity.[1] Lately,
Catalytic C C s-bond cleavage followed by alkyne
insertion is of significant synthetic value particularly because
it can introduce an olefin moiety which permits further
functionalization of the substrate.[12] Alkyne insertion into the
saturated cyclobutanones, thus giving cyclohexones, was first
reported by Murakami et al. using a nickel catalyst, and a b-
À
cleavage of a C C bond followed by insertion of an
unsaturated unit serves as a rapid and atom-economical[2]
approach for constructing homologated or ring-expanded
products.[3,1l] In particular, the synthesis of fused-ring systems
is benefited by this strategy. For instance, we recently
developed a rhodium-catalyzed intramolecular carboacyla-
tion of olefins with benzocyclobutenones to construct chiral
polyfused scaffolds.[4] Good yields and excellent regio- and
enantioselectivity were obtained with a broad range of
substrates. Such a “cut and sew” transformation[5] involves
À
carbon elimination mechanism is proposed for the C C
activation step (Scheme 2A).[12e,13] For the unsaturated cyclo-
butenones, given their unsymmetrical structures, a site-selec-
[10]
À
tivity issue arises concerning which C C bond to cleave.
The intermolecular alkyne insertion into cyclobutenones was
previously known to occur either by thermal heating[14] or
through catalysis using nickel[15] or rhodium.[16] In all these
À
À
oxidative addition of a metal into the a C C bond of a cyclic
cases, the C1 C4 bond is cleaved through a vinyl ketene
intermediate. For the intramolecular alkyne insertion, we
hypothesized that: 1) the alkyne group would serve as
ketone to generate a key acylmetallacycle intermediate (B),
which, followed by an intramolecular migratory insertion and
reductive elimination, provides the fused-ring system C
(Scheme 1).
À
a directing group and guide metals to cleave the C1 C2
bond of benzocyclobutenones (Scheme 2B),[4] which, in turn,
provides different site selectivity from that of the intermo-
lecular insertion; 2) the resulting “cut and sew” products,
conjugated enones, would undergo spontaneous tautomeriza-
tion to give b-naphthols as the ultimate products.
On the other hand, it is well established that the acylmetal
complexes (i.e. intermediate B) can also undergo reversible
CO de-insertion reactions.[6,7] Thus, complementary to the
direct insertion reaction (regular “cut and sew”), the corre-
sponding decarbonylative “cut and sew” would provide an
To test our hypothesis, we started with benzocyclobute-
none 1a as a model substrate (see Table S1 in the Supporting
Information; see Table 1 for structures). Wilkinsonꢀs catalyst
[*] P.-H. Chen, Dr. T. Xu, Prof. Dr. G. Dong
Department of Chemistry and Biochemistry
University of Texas at Austin
100 east 24th street, Austin, TX 78712 (USA)
E-mail: gbdong@cm.utexas.edu
Homepage: http://gbdong.cm.utexas.edu/
[**] We thank UT Austin and CPRIT for start-up funds, and the Welch
Foundation (F 1781) for research grants. G.D. thanks ORAU for
a New Faculty Enhancement Award. G.D. is a Searle Scholar. We
also thank Prof. Siegel for helpful discussions, and Professors
Sessler, Siegel, and Anslyn for the loan of chemicals. Dr. Lynch is
acknowledged for X-ray crystallography. We thank Johnson Matthey
for a generous donation of Rh salts.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201310100.
Scheme 1. A divergent approach for fused-ring synthesis: Regular and
decarbonylative cyclization.
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Table 1: Substrate scope for direct alkyne Insertion.[a]
Entry
Substrate
Product
Yield
[%][b]
1
2
3
4
5
6
7
8
9
1a
1b
1c
1d
1e
1 f
1g
1h
1i
R1 =Et
2a
2b
2c
2d
2e
2 f
2g
2h
2i
R1 =Et
93
86
53
67
93
40
77
83
78
R2 =H
R2 =H
R1 =Ph
R1 =Ph
R2 =H
R2 =H
R1 =TMS
R2 =H
R1 =TMS
R2 =H
R1 =Me
R2 =H
R1 =Me
R2 =H
R1 =p-C6H4OMe
R2 =H
R1 =p-C6H4OMe
R2 =H
R1 =p-C6H4NO2
R2 =H
R1 =p-C6H4NO2
R2 =H
R1 =p-C6H4F
R2 =H
R1 =p-C6H4F
R2 =H
À
Scheme 2. C C bond cleavage in cyclobutenones and cyclobutanones.
R1 =Et
R1 =Et
R2 =Me
R1 =Et
R2 =Me
R1 =Et
R2 =CO2Me
R2 =CO2Me
10
1j
2j
23[c]
11
1k
2k
56
[a] Reaction conditions: [{Rh(cod)Cl}2] (5 mol%), dppp (12 mol%), 1,4-
dioxane, 1308C, 24 h, sealed vial. [b] Yields of isolated products. [c] 27%
of 1j was recovered; with 0.1 equiv of ZnCl2 added, only 13% yield of 2j
was isolated. cod=1,5-cyclooctadiene, TMS=trimethylsilyl.
Figure 1. Representative examples of related bioactive molecules.
[RhCl(PPh3)3] was initially investigated, and the desired b-
naphthol 2a was isolated, albeit in low yield. Given the
importance of bidentate ligands in the related olefin insertion
reaction,[4] a series of bidentate phosphine ligands were
examined. l,3-Bis(diphenylphosphanyl)propane (dppp) was
found to be most efficient, while the one-carbon unit longer
1,4-bis(diphenylphosphino)butane (dppb) or shorter 1,2-bis-
(diphenylphosphino)ethane (dppe) ligand was less effective.
A survey of different solvents revealed that 1,4-dioxane
provided the highest yield for this transformation, whereas
using other solvents resulted in different degrees of decom-
position of the starting material or product.
With the optimized reaction conditions in hand, the scope
of this reaction was examined (Table 1). Substrates containing
alkyl, aryl, or alkenyl alkynes were converted into the
corresponding b-naphthols in good to excellent yields.[17]
Both electron-donating and electron-withdrawing substitu-
ents on the benzocyclobutenone rings were well tolerated
(entries 8 and 9, Table 1). Moreover, a number of functional
groups were found to be compatible with this transformation,
including esters, ethers, trimethylsilyl, nitro groups, aryl
fluorides, and conjugated olefins (entries 3, 5–7, 9 and 11,
Table 1). Substitution at the C8-position of the benzocyclo-
butenone slowed the reaction, but the desired polysubstituted
naphthol 2j was nevertheless obtained (entry 10, Table 1).
The alkynes 1l/1m are more challenging substrates because
the formation of six/seven-membered rings are kinetically less
favorable compared to forming five-membered rings [Eq. (1)
in Table 2]. Indeed, under the optimized reaction conditions,
low conversions were observed for these substrates. However,
we recently discovered that using a Lewis acid as a cocatalyst
can dramatically enhance the reaction rate of olefin carboa-
cylation, likely because of its coordination with the carbonyl
group promoting both oxidative addition and reductive
elimination.[4a,18]
Thus, we hypothesized that the related alkyne insertion
would benefit from this Lewis-acid effect. To our delight,
when 1 equivalent of ZnCl2 was employed as an additive,
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Table 2: ZnCl2 as an additive in the formation of six- and seven-
membered rings.
less effective in promoting the direct alkyne insertion reaction
for substrate 1l,[22] and likely to be a result of a less favorable
reductive elimination step from the seven-membered acyl-
metallacycle intermediate (Scheme 2B). Having examined
a number of different solvents, mixed xylenes proved to be the
optimal solvent. Finally, with a slight increase of the catalyst
loading, the decarbonylative product, the fused-indene 3l (see
Table 3), was isolated in 64% yield.
1l n=1, R=Et
The substrate scope for the decarbonylative alkyne
insertion was then examined (Table 3).[23] In general,
a range of indene-based fused rings were obtained in decent
yields. Compared to the ethyl-substituted alkynes, when the
aryl-substituted alkynes were employed as the coupling
partner, the yields for the decarbonylative insertion were
significantly increased (entries 2–7, and 11, Table 3), and is
consistent with our earlier observation of the low cyclization
rate of phenyl-substituted substrates (e.g. 1m) in the absence
of ZnCl2 [Eq. (1)]. The ortho-methyl-substituted phenyl
substrate 1t gave lower yield, and is likely a result of
without ZnCl2
with 10 mol% ZnCl2
with 1 equiv ZnCl2
with 1 equiv ZnCl2, but no [{Rh(cod)Cl}2]/dppp
70%, 48h
81%, 24h
91%, 24h
0%, 24h
1m
1n
n=1, R=Ph
without ZnCl2
with 10 mol% ZnCl2
with 1 equiv ZnCl2
4%, 24h
89%, 24h
91%, 24h
n=2, R=Ph
without ZnCl2
with 10 mol% ZnCl2
with 1 equiv ZnCl2,
0%, 24h
64%, 24h
77%, 24h
7.5 mol% [{Rh(cod)Cl}2], 18 mol% dppp
Table 3: Substrate scope for decarbonylative alkyne insertion.[a]
good to excellent yields of the six- and seven-membered fused
rings were obtained [Eq. (1)]. A catalytic amount of ZnCl2
(10 mol%) was also found to be effective, albeit with a slightly
lower yield. We also found ZnCl2 itself did not catalyze the
reaction. The structure of 2l was unambiguously character-
ized by X-ray crystallography (see the Supporting Informa-
tion).
Entry
Substrate
Product
Yield [%][b]
Although the direct decarbonylation of cyclobutanones to
give cyclopropanes (ring contraction) has been known for
almost two decades since the seminal work by Murakami, Ito,
1
1l
R1 =Et
R2 =H
3l
R1 =Et
R2 =H
64
and co-workers,[19] C C cleavage with subsequent decarbon-
À
2
1m R1 =Ph
R2 =H
3m R1 =Ph
83
R2 =H
ylation and insertion of an unsaturated moiety has been much
underdeveloped. The intermolecular decarbonylative cou-
plings of cyclobutenediones and cyclobutenones with norbor-
nene and ethylene were first reported by Kondo, Mitsudo, and
co-workers,[8] and the only example of an intramolecular
coupling of squaric acid derivatives and olefins was described
by Yamamoto et al.[9] However, to the best of our knowledge,
the decarbonylative coupling between any cyclic ketones and
alkynes was previously unknown.[20]
3
1o R1 =p-C6H4OMe
R2 =H
3o R1 =p-C6H4OMe
R2 =H
64 (68)
75
4
1p R1 =p-C6H4F
R2 =H
3p R1 =p-C6H4F
R2 =H
5
1q R1 =p-C6H4Cl
R2 =H
3q R1 =p-C6H4Cl
R2 =H
75
6
1r
R1 =1-naphthyl
R2 =H
3r
R1 =1-naphthyl
R2 =H
76
7
1s R1 =p-C6H4CO2Me 3s R1 =p-C6H4CO2Me 62
R2 =H
R2 =H
The proposed decarbonylative “cut and sew” transforma-
tion (Scheme 2B) was explored using 1l as the model
substrate. Given the challenge of removing CO from the
metal center, an open system reflux under an argon atmos-
phere with high-boiling-point solvents was chosen to facilitate
CO extrusion from the reaction vessel (see Table S2).[21]
Although using PPh3 as the ligand provided a good con-
version, it suffered from poor selectivity of the decarbon-
ylative insertion versus the direct insertion. A number of
bidentate phosphine ligands were subsequently investigated.
Interestingly, the chiral DTBM-segphos provided the highest
conversion and yield for the desired indene product.
Although the exact reason why DTBM-segphos facilitates
the decarbonylation pathway is unclear, control experiments
indicated this four-carbon-linked bidentate ligand was much
8
1t
R1 =o-C6H4Me
R2 =H
3t
R1 =o-C6H4Me
R2 =H
28 (33)
57( 62)
56
9
1u R1 =Et
R2 =Me
3u R1 =Et
R2 =Me
10
11
1v R1 =Et
3v R1 =Et
R2 =CO2Et
R2 =CO2Et
1w R1 =Ph
R2 =Me
3w R1 =Ph
R2 =Me
68 (73)
12
1n
3n
23 (48)
[a] Reaction conditions: [{Rh(cod)Cl}2] (7.5 mol%), DTBM-segphos
(18 mol%), xylenes, reflux, 48 h. [b] Yields of isolated products. Values
within parentheses are yields based on recovered starting material.
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Cramer, Angew. Chem. 2011, 123, 7884; Angew. Chem. Int. Ed.
unfavorable steric interactions during the cyclization (entry 8,
Table 3). In addition, the seven-membered-ring fused indene
product was also obtained (entry 12, Table 3). The structure
of indene 3o was unambiguously characterized by X-ray
crystallography (see the Supporting Information).
2011, 50, 7740; l) M. Murakami, T. Matsuda, Chem. Commun.
2011, 47, 1100; m) T. Seiser, N. Cramer, Org. Biomol. Chem.
2009, 7, 2835; n) N. Cramer, T. Seiser, Synlett 2011, 449; o) C.
Aissa, Synthesis 2011, 3389.
[2] B. M. Trost, Science 1991, 254, 1471.
À
[3] For the seminal work of catalytic C C bond activation with
subsequent insertion of olefins or alkynes: for biphenylenes, see:
a) B. L. Edelbach, R. J. Lachicotte, W. D. Jones, Organometallics
1999, 18, 4040; b) for cyclobutenones, see: M. A. Huffman, L. S.
Liebeskind, J. Am. Chem. Soc. 1990, 112, 8617; for cyclobute-
nediones, see: c) M. S. South, L. S. Liebeskind, J. Am. Chem.
Soc. 1984, 106, 4181; for cyclobutanones, see: d) M. Murakami,
T. Itahashi, Y. Ito, J. Am. Chem. Soc. 2002, 124, 13976; for linear
ketones, see: e) A. M. Dreis, C. J. Douglas, J. Am. Chem. Soc.
2009, 131, 412; for cyclopropanes: f) K. Narasaka, Y. Koga,
Chem. Lett. 1999, 28, 705; for cyclopropenes: g) C. Li, H. Zhang,
J. Feng, Y. Zhang, J. Wang, Org. Lett. 2010, 12, 3082; for
vinylcyclopropanes: h) L. Jiao, M. Lin, L.-G. Zhuo, Z.-X. Yu,
Org. Lett. 2010, 12, 2528; i) P. A. Wender, H. Takahashi, B.
Witulski, J. Am. Chem. Soc. 1995, 117, 4720; for amino cyclo-
propanes: j) M. H. Shaw, E. Y. Melikhova, D. P. Kloer, W. G.
Whittingham, J. F. Bower, J. Am. Chem. Soc. 2013, 135, 4992; for
cyclobutenols, see: k) N. Ishida, S. Sawano, Y. Masuda, M.
Murakami, J. Am. Chem. Soc. 2012, 134, 17502; for methylene-
cyclopropanes: l) H.-J. Weintz, P. Binger, Tetrahedron Lett. 1985,
In conclusion, we have developed a divergent approach to
access fused b-naphthol and indene rings by the rhodium-
À
26, 4075; for C CN bond cleavage, see: m) Y. Nakao, S. Oda, T.
À
catalyzed C C activation of benzocyclobutenones [Eq. (2)].
Hiyama, J. Am. Chem. Soc. 2004, 126, 13904.
The unique selectivity of cleaving the usually less-reactive
[4] a) T. Xu, G. Dong, Angew. Chem. 2012, 124, 7685; Angew. Chem.
Int. Ed. 2012, 51, 7567; b) T. Xu, H.-M. Ko, N. Savage, G. Dong, J.
Am. Chem. Soc. 2012, 134, 20005.
[5] We use the term of “cut and sew” to describe this stepwise/
tandem transformation for convenience, and obviously, numer-
ous different types of reactions fall into this category. For the
À
C1 C2 bond distinguishes this direct alkyne insertion from
other cyclobutenone–alkyne couplings.[14,15] It is also distinct
from the saturated cyclobutanone-[12e] and cyclobutenol-
mediated[3k,12f] alkyne insertion reactions because of their
different mechanistic feature. Furthermore, it illustrates that
the feasibility of a decarbonylative “cut and sew” pathway
À
examples that involve C C bond activation, see
Ref. [3,4,1l,12,14—16,18].
À
with C C activation of benzocyclobutenones, enables an
[6] J. F. Hartwig, Organotransition Metal Chemistry: from Bonding
to Catalysis, University Science Books Mill Valley, Mill Valley,
2009.
unusual [4+2À1] transformation. Finally, it demonstrates that
the selectivity for either the direct or decarbonylative
insertion can be controlled by choosing different ligands
and other reaction conditions. Efforts towards expansion of
the reaction scope (i.e. nitrogen-containing fused rings by
both alkene and alkyne insertion), detailed mechanistic
studies to enhance the catalyst activity, and application of
this method to synthesize bioactive molecules are in prog-
ress.[24]
À
[7] For a recent review of decarbonylative C C-forming reactions,
see: A. Dermenci, G. Dong, Sci. China Chem. 2013, 56, 685.
[8] For an intermolecular decarbonylative coupling between cyclo-
butendiones/cyclobutenones and norbornene/ethylene, see:
a) K. Teruyuki, N. Ayako, O. Takumi, S. Nobuyoshi, W. Kenji,
M. Takeaki, J. Am. Chem. Soc. 2000, 122, 6319; b) T. Kondo, Y.
Taguchi, Y. Kaneko, M. Niimi, T.-A. Mitsudo, Angew. Chem.
2004, 116, 5483; Angew. Chem. Int. Ed. 2004, 43, 5369.
[9] For a single report of the intramolecular decarbonylative alkene
insertion with squaric acid derivatives, see: Y. Yamamoto, S.
Kuwabara, H. Hayashi, H. Nishiyama, Adv. Synth. Catal. 2006,
348, 2493.
Received: November 20, 2013
Published online: January 21, 2014
À
Keywords: alkynes · C C functionalization · cyclization ·
[10] For a seminal mechanistic study on the metal cleavage of
.
À
benzocyclobutenone C C bond, see: a) M. A. Huffman, L. S.
rhodium · synthetic methods
Liebeskind, W. T. Pennington, Organometallics 1990, 9, 2194;
b) M. A. Huffman, L. S. Liebeskind, W. T. Pennington, Organo-
metallics 1992, 11, 255.
[11] For selected recent reviews, see: a) C. K. Marisa, J. M. Barbara,
C. L. Elizabeth, Chem. Soc. Rev. 2009, 38, 3193; b) M. Enders,
R. W. Baker, Curr. Org. Chem. 2006, 10, 937; c) S. Toyota, T.
Iwanaga, Sci. Synth. 2008, 45, 745; d) Y. Kuninobu, Y. Nishina,
A. Kawata, M. Shouho, K. Takai, Pure Appl. Chem. 2008, 80,
1149.
[12] For representative alkyne insertion examples with biphenylenes,
see: Ref. [3a] and a) T. Schaub, U. Radius, Chem. Eur. J. 2005, 11,
5024; b) T. Shibata, G. Nishizawa, K. Endo, Synlett 2008, 765;
À
[1] For recent reviews of C C bond activation, see: a) B. Rybtch-
inski, D. Milstein, Angew. Chem. 1999, 111, 918; Angew. Chem.
Int. Ed. 1999, 38, 870; b) M. Murakami, Y. Ito, Top. Organomet.
Chem. 1999, 3, 97; c) M. E. van der Boom, D. Milstein, Chem.
Rev. 2003, 103, 1759; d) C.-H. Jun, Chem. Soc. Rev. 2004, 33, 610;
e) T. Satoh, M. Miura, Top. Organomet. Chem. 2005, 14, 1; f) C.-
H. Jun, J.-W. Park, Top. Organomet. Chem. 2007, 24, 117; g) D.
Necas, M. Kotora, Curr. Org. Chem. 2007, 11, 1566; h) A.
Korotvicka, D. Necas, M. Kotora, Curr. Org. Chem. 2012, 16,
1170; i) R. H. Crabtree, Chem. Rev. 1985, 85, 245; j) W. D. Jones,
Nature 1993, 364, 676; k) T. Seiser, T. Saget, D. N. Tran, N.
ˇ
ˇ
c) A. Korotvicka, I. Cꢁsarovꢂ, J. Roithovꢂ, M. Kotora, Chem.
Eur. J. 2012, 18, 4200. For representative examples with cyclo-
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.
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Communications
butenediones and cyclobutanones: d) L. S. Liebeskind, S. L.
Baysdon, M. S. South, S. Iyer, J. P. Leeds, Tetrahedron Lett. 1985,
41, 5839; e) M. Murakami, S. Ashida, T. Matsuda, J. Am. Chem.
Soc. 2005, 127, 6932; For representative examples with cyclo-
butenols, see: Ref. [3k] and f) T. Matsuda, N. Miura, Org.
Biomol. Chem. 2013, 11, 3424; For examples with azetidinones,
see: g) K. Y. T. Ho, C. Aꢃssa, Chem. Eur. J. 2012, 18, 3486; h) P.
Kumar, J. Louie, Org. Lett. 2012, 14, 2026; i) N. Ishida, T. Yuhki,
M. Murakami, Org. Lett. 2012, 14, 3898; For representative
examples with alkyne insertion into C-CN bond, see: Ref. [3m],
and j) Y. Nakao, A. Yada, S. Ebata, T. Hiyama, J. Am. Chem.
Soc. 2007, 129, 2428; k) Y. Hirata, T. Yukawa, N. Kashihara, Y.
Nakao, T. Hiyama, J. Am. Chem. Soc. 2009, 131, 10964; l) Y.
Nakao, A. Yada, T. Hiyama, J. Am. Chem. Soc. 2010, 132, 10024;
m) Y. Hirata, A. Yada, E. Morita, Y. Nakao, T. Hiyama, M.
Ohashi, S. Ogoshi, J. Am. Chem. Soc. 2010, 132, 10070; n) N. R.
Rondla, S. M. Levi, J. M. Ryss, R. A. V. Berg, C. J. Douglas, Org.
Lett. 2011, 13, 1940; o) A. Yada, T. Yukawa, Y. Nakao, T.
Hiyama, Chem. Commun. 2009, 3931; p) For a review of
insertion into cyclopropanes, cyclopropenes. and vinylcyclopro-
panes, see: M. Rubin, M. Rubina, V. Gevorgyan, Chem. Rev.
2007, 107, 3117, and references therein.
derived substrate also afforded the desired “cut and sew” lactone
product, albeit in a low yield (22% without ZnCl2, 28% with
0.1 equiv of ZnCl2).
[18] For seminal work of using Lewis acids in promoting catalytic
carbocyanation reactions, see:, Ref. [12j] and a) N. M. Brunkan,
D. M. Brestensky, W. D. Jones, J. Am. Chem. Soc. 2004, 126,
3627; b) C. A. Tolman, R. J. McKinney, W. C. Seidel, J. D.
Druliner, W. R. Stevens, Adv. Catal. 1985, 33, 1; c) Y. Nakao, S.
Ebata, A. Yada, T. Hiyama, M. Ikawa, S. Ogoshi, J. Am. Chem.
Soc. 2008, 130, 12874; d) M. P. Watson, E. N. Jacobsen, J. Am.
Chem. Soc. 2008, 130, 12594; e) A. Minami, H. Yoshiyasu, Y.
Nakao, T. Hiyama, Angew. Chem. 2013, 125, 917 – 921; Angew.
Chem. Int. Ed. 2013, 52, 883 – 887.
[19] For examples of catalytic decarbonylation of cyclobutanones to
give cyclopropanes, see: a) M. Murakami, H. Amii, Y. Ito,
Nature 1994, 370, 540; b) M. Murakami, H. Amii, K. Shigeto, Y.
Ito, J. Am. Chem. Soc. 1996, 118, 8285; c) T. Matsuda, M.
Shigeno, M. Murakami, Chem. Lett. 2006, 35, 288.
[20] For an aldehyde-mediated decarbonylative coupling with
alkynes, see: a) X. Guo, J. Wang, C. J. Li, J. Am. Chem. Soc.
2009, 131, 15092; b) X. Guo, J. Wang, C. J. Li, Org. Lett. 2010, 12,
3176.
[13] A recent DFT calculation suggests an alternative oxidative
addition mechanism for the alkyne insertion into azetidinones,
see: Y. Li, Z. Lin, Organometallics 2013, 32, 3003.
[14] a) R. L. Danheiser, S. K. Gee, J. Org. Chem. 1984, 49, 1672;
b) R. L. Danheiser, A. Nishida, S. Savariar, M. P. Trova,
Tetrahedron Lett. 1988, 29, 4917.
[15] For catalytic examples, see: a) M. A. Huffman, L. S. Liebeskind,
J. Am. Chem. Soc. 1991, 113, 2771; b) A-L. Auvinet, J. P. A.
Harrity, Angew. Chem. 2011, 123, 2821; Angew. Chem. Int. Ed.
2011, 50, 2769.
[16] T. Kondo, M. Niimi, M. Nomura, K. Wada, T.-A. Mitsudo,
Tetrahedron Lett. 2007, 48, 2837.
[21] A. Dermenci, R. E. Whittaker, G. Dong, Org. Lett. 2013, 15,
2242.
[22] When the substrate 1l was subjected to the optimized reaction
conditions for direct alkyne insertion, but using DTBM-segphos
as the ligand, 3l was isolated only in 22% yield (along with
indene 3l in 12% yield). In contrast, the dppp ligand gave a 70%
yield with no decarbonylation product observed [Eq. (1)].
[23] The propargyl ether substrates, that is, 1a, did not provide any
indene product, likely because significant ring strain would be
generated if the five-membered fused-indene product was
formed.
[24] CCDC 967148 (2l) and 967149 (3o) contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
[17] Terminal-alkyne-based substrates gave a complex mixture of
products, likely to be a result of the competitive formation of
rhodium vinylidene intermediates. The phenylpropiolic-acid-
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