Double 1,4-rhodium migration cascade in rhodium-catalysed arylative ring-opening/spirocyclisation of (3-arylcyclobutylidene)acetates

Article abstract of DOI:10.1039/c2cc18098g

1,4-Rhodium migration occurs twice during the course of the rhodium-catalysed arylative ring-opening/spirocyclisation reaction of (3-arylcyclobutylidene)acetates with sodium tetraarylborates to afford ketones possessing a 1,1′-spirobiindane skeleton.

Full text of DOI:10.1039/c2cc18098g

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COMMUNICATION
Double 1,4-rhodium migration cascade in rhodium-catalysed arylative
ring-opening/spirocyclisation of (3-arylcyclobutylidene)acetatesw
Takanori Matsuda,* Yuya Suda and Akira Takahashi
Received 27th December 2011, Accepted 30th January 2012
DOI: 10.1039/c2cc18098g
1,4-Rhodium migration occurs twice during the course of the
rhodium-catalysed arylative ring-opening/spirocyclisation reaction
of (3-arylcyclobutylidene)acetates with sodium tetraarylborates to
afford ketones possessing a 1,10-spirobiindane skeleton.
(2a, 1 equiv.) in toluene at 110 1C in the presence of a catalytic
amount of [RhCl(cod)]2 (5 mol%, cod = cycloocta-1,5-diene)
(eqn (1)). After 2 h, 1a was completely consumed, and ketone
3aa possessing a 1,10-spirobiindane skeleton was obtained in
80% yield by chromatographic purification. Longer reaction
time led to the formation of tert-alcohol 4 as a byproduct of
the 1,2-addition of 2a to the carbonyl group of 3aa. Indeed, the
reaction of 1a with three equivalents of 2a for 3 h at 115 1C
resulted in the exclusive formation of 4 in 57% yield (eqn (2)).10
1,4-Migration of transition metals is a useful synthetic tool for
intramolecular activation of neighbouring C–H bonds and has
been exploited in the construction of complex organic frame-
works.1 The 1,4-rhodium migrations reported so far involved
alkenyl to aryl2,3 and alkyl to aryl migration processes
(Scheme 1).4–6 In the latter case, 1,4-rhodium migration occurs
with b-phenethylrhodium(I) species lacking b-hydrogens that
are prone to undergo possible b-hydride elimination. Such
alkylrhodium(I) species were generated in situ by addition of
arylrhodium(I) species to norbornene4 and b,b-disubstituted
a,b-unsaturated esters,5 and b-carbon elimination of rhodium(I)
cyclobutanolates.6 In particular, the alkyl to aryl migration offers an
attractive opportunity for the regeneration of active arylrhodium(I)
species from alkylrhodium(I) species, which are generally inactive
towards electrophiles. Herein, we report a rhodium(I)-catalysed
arylative ring-opening/spirocyclisation reaction of (3-arylcyclo-
butylidene)acetates that constructs 1,10-spirobiindane skeletons
through a mechanism involving two successive alkyl to aryl
1,4-rhodium migration processes. b-Phenethylrhodium(I) species
amenable to the 1,4-rhodium migrations are generated from the
b-carbon elimination of (cyclobutylmethyl)rhodium(I) and intra-
molecular 1,4-addition to b-substituted cinnamate.
ð1Þ
ð2Þ
The formation of spirobiindanone 3aa can be explained by
assuming the reaction pathway shown in Scheme 2. Initially,
arylrhodium(I) species A generated by transmetalation between
2a and a rhodium complex adds to 1a in a 1,4-fashion to give
(cyclobutylmethyl)rhodium(I) B. Then, b-carbon elimination
occurs with B, opening the four-membered ring and regenerating an
a,b-unsaturated ester moiety. Subsequently, 1,4-rhodium migration
occurred with the resulting b-phenethylrhodium(I) C to generate
arylrhodium(I) D, which undergoes a second 1,4-addition to form a
five-membered ring. The b-phenethylrhodium(I) E that formed
again affords arylrhodium(I) F via the second 1,4-rhodium
migration. Finally, arylrhodium(I) F adds to the ester group
and furnishes spirocycle G as a rhodium(I) alkoxide. b-Oxygen
elimination accomplishes acylation to give 3aa with concomitant
generation of a catalytically active rhodium(I) methoxide H. Note
that the spirobiindane skeleton was constructed via ordered
sequential steps consisting of two 1,4-additions, two b-eliminations,
two 1,4-rhodium migrations and a 1,2-addition. Furthermore,
two distinct selectivities enable the ring-opening/spirocyclisation:
(1) b-carbon elimination is more prone to occur for B rather than
We initiated our study by exploring the addition of an
arylrhodium(I) species7 to cyclobutylideneacetates in an attempt
to cause the ring-opening of the cyclobutane ring by b-carbon
elimination.8 Methyl(3-methyl-3-phenylcyclobutylidene)acetate9
(1a) was subjected to a reaction with sodium tetraphenylborate
Scheme 1 1,4-Rhodium migration.
Department of Applied Chemistry, Tokyo University of Science,
1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
E-mail: mtd@rs.tus.ac.jp; Fax: +81 3 5261 4631
w Electronic supplementary information (ESI) available: Experimental
procedures and characterisation data for new compounds. See DOI:
10.1039/c2cc18098g
c
2988 Chem. Commun., 2012, 48, 2988–2990
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Scheme 2 Proposed mechanism for arylative ring-opening/spirocyclization of 1a with 2a.
1,4-migration to form an arylrhodium species; and (2) 1,4-rhodium
migration to form F is more favourable than migration onto the
indane benzene ring presumably because of the steric reason.
Control experiments indicated that almost no reaction
occurred with phenylboronic acid instead of 2a and that the
reaction carried out at lower temperatures failed to afford 3aa.
In addition, the reaction with methyl(3-phenylcyclobutylidene)-
acetate gave a complex mixture of products in which a spirocyclic
product was not observed. The absence of hydrogen at the
3 position of the cyclobutane ring of 1 plays a pivotal role in the
reaction so as to avoid the unproductive b-hydride elimination
pathway.
Table 1 Rhodium-catalysed arylative ring-opening/spirocyclisation
of cyclobutylideneacetate 1a with various sodium tetraarylborates 2a
Entry
2
3
Yieldb (%)
Other tetraarylborates also reacted with 1a under similar
conditions (Table 1). 4-Substituted tetraarylborates provided the
corresponding 5-substituted 30,30-dimethylspirobiindanones 3ab–ae
in 41–79% yields (entries 1–4). The electron rich 4-methoxyphenyl
borate 2c allowed the formation of the corresponding spirocycle
3ac in higher yield. For the reaction with 4-chlorophenyl borate 2e,
the addition of 1,3-bis(diphenylphosphino)propane (DPPP) as the
ligand was essential for obtaining the product 3ae in a reasonable
yield. Reaction of 1a with 3-methylphenyl borate 2f led to the
regioselective formation of 6-methyl-30,30-dimethylspirobiindanone
3af through the second 1,4-rhodium migration at the less hindered
C6 carbon (entry 5), whereas 2-methylphenyl borate could not be
used as the arylating agent. 2-Naphthyl borate 2g also participated
in the reaction to give the corresponding spirocyclic ketone 3ag in
51% yield (entry 6). Moreover, the second 1,4-rhodium migration
exclusively occurred at the less hindered C3 carbon.
1
2
3
4
2b (Ar = 4-MeC6H4)
2c (Ar = 4-MeOC6H4)
2d (Ar = 4-CF3C6H4)
2e (Ar = 4-ClC6H4)
3ab (R = Me)
3ac (R = OMe)
3ad (R = CF3)
3ae (R = Cl)
70
79
41
66c
5
2f (Ar = 3-MeC6H4)
57
We next examined the scope of the reaction with respect to
cyclobutylideneacetates with borate 1a (Table 2). The reaction
of cyclobutylideneacetates having 4-methylphenyl (1b) and
4-chlorophenyl groups (1c) at the 3 position of the cyclobutane
ring gave the corresponding 60-substituted spirobiindanes 3ba
(65%) and 3ca (48%), respectively (entries 1 and 2). The 2-thienyl
group was tolerated as the aryl group at the 3 position (entry 3).
The diastereoselectivity issue arises if cyclobutylideneacetates
have no methyl group (R1 a Me) at the 3 position. When
methyl(3-ethyl-3-phenylcyclobutylidene)acetate (1e) was used
as the substrate, a 68: 32 mixture of diastereomers was obtained
in 64% yield (entry 4). An NOE experiment revealed that the
methyl and methylene groups are located on the same side of
the five-membered ring of 3ea in the major product. In the case
of 3,3-diphenyl derivative 1f, the product 3fa was obtained in
6
2g (Ar = 2-naphthyl)
51
a
Unless otherwise noted, 1a (0.10 mmol) and 2 (0.10 mmol) were reacted in
toluene (1.0 mL) in the presence of [RhCl(cod)]2 (5.0 mmol, 10 mol% Rh).
b Isolated yield. c DPPP (10 mmol) was added as the ligand.
high yield as an equimolar mixture of diastereomers (entry 5).
Substrate 1g possessing a tetrasubstituted alkene moiety failed
to react under the reaction conditions (entry 6).
The reactivity of conjugated methylenecyclobutane derivatives
other than esters was also explored. Cyclobutylideneacetone 5
reacted with 2a in the presence of a rhodium catalyst in toluene
c
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Table 2 Arylative ring-opening/spirocyclisation of cyclobutylidenea-
cetates 1 with 2aa
In summary, we have developed a catalytic spirocyclisation
reaction forming 1,10-spirobiindan-3-ones via a 1,4-rhodium
migration cascade. During the course of the reaction, the
rhodium moves about more than once, accompanying the
one C–C bond cleavage, two C–H bond cleavages and three
C–C bond formations to assemble the spirobiindane skeleton
of 3
This work was supported by a Grant-in-Aid for Scientific
Research for Young Scientist (B) (No. 23750115) from
the Ministry of Education, Culture, Sports, Science and
Technology, Japan.
Entry
1 (R1, R2)
3
Yieldb (%)
1
2
1b (Me, Me)
1c (Me, Cl)
3ba
3ca
65
48
Notes and references
1 For reviews, see: (a) S. Ma and Z. Gu, Angew. Chem., Int. Ed.,
2005, 44, 7512; (b) F. Shi and R. C. Larock, Top. Curr. Chem.,
2010, 292, 123.
3
57
2 For 1,4-rhodium migration occurring with (Z)-2-phenylvinylrhodium(I),
see: (a) T. Hayashi, K. Inoue, N. Taniguchi and M. Ogasawara,
J. Am. Chem. Soc., 2001, 123, 9918; (b) T. Miura, T. Sasaki,
H. Nakazawa and M. Murakami, J. Am. Chem. Soc., 2005,
127, 1390; (c) R. Shintani, S. Isobe, M. Takeda and T. Hayashi,
Angew. Chem., Int. Ed., 2010, 49, 3795.
4
5
1e (Et, H)
1f (Ph, H)
3ea
3fa
63c
88d
3 For 1,4-rhodium migration occurring with 1-benzoylvinylrhodium(I),
see: (a) R. Shintani, K. Okamoto and T. Hayashi, J. Am. Chem. Soc.,
2005, 127, 2872; (b) H. Yamabe, A. Mizuno, H. Kusama and
N. Iwasawa, J. Am. Chem. Soc., 2005, 127, 3248; (c) R. Shintani and
T. Hayashi, Org. Lett., 2005, 7, 2071; (d) R. Shintani, K. Takatsu and
T. Hayashi, Angew. Chem., Int. Ed., 2007, 46, 3735; (e) R. Shintani,
K. Takatsu, T. Katoh, T. Nishimura and T. Hayashi, Angew. Chem.,
Int. Ed., 2008, 47, 1447.
6
0
a
1 (0.10 mmol) and 2 (0.10 mmol) were reacted in toluene (1.0 mL) in
b
4 K. Oguma, M. Miura, T. Satoh and M. Nomura, J. Am. Chem.
Soc., 2000, 122, 10464.
the presence of [RhCl(cod)]2 (5.0 mmol, 10 mol% Rh). Isolated yield.
Obtained as a 68 : 32 diastereomeric mixture. Obtained as a 51 : 49
diastereomeric mixture.
c
d
5 R. Shintani and T. Hayashi, Org. Lett., 2011, 13, 350.
6 (a) T. Matsuda, M. Shigeno and M. Murakami, J. Am. Chem. Soc.,
2007, 129, 12086; (b) T. Seiser, O. A. Roth and N. Cramer, Angew.
Chem., Int. Ed., 2009, 48, 6320; (c) M. Shigeno, T. Yamamoto and
M. Murakami, Chem.–Eur. J., 2009, 15, 12929.
7 For reviews on rhodium-catalysed addition reactions of organoboron
compounds, see: (a) K. Fagnou and M. Lautens, Chem. Rev., 2003,
103, 169; (b) T. Hayashi and K. Yamasaki, Chem. Rev., 2003,
103, 2829; (c) T. Miura and M. Murakami, Chem. Commun., 2007,
217; (d) S. W. Youn, Eur. J. Org. Chem., 2009, 2597;
(e) H. J. Edwards, J. D. Hargrave, S. D. Penrose and C. G. Frost,
Chem. Soc. Rev., 2010, 39, 2093.
at 130 1C to provide the desired tert-alcohol 611 in 29% yield
along with the usual 1,4-addition products 7 (B20%) as a 1 : 1
diastereomeric mixture (eqn (3)).12 In contrast, spirocyclisation
failed to occur with cyclobutylideneacetonitrile 8, which gave
indan-1-ylacetonitrile 9 and a mixture of diastereomers of
cyclobutylacetonitrile 10 (eqn (4)).13
8 For reviews on b-carbon elimination, see: (a) M. Miura and
T. Satoh, Top. Organomet. Chem., 2005, 14, 1; (b) T. Seiser and
N. Cramer, Org. Biomol. Chem., 2009, 7, 2835; (c) M. Murakami
and T. Matsuda, Chem. Commun., 2011, 47, 1100.
9 Cyclobutylideneacetates
1 are easily synthesised from the
Wittig-type olefination of the corresponding cyclobutanones with
methyl(triphenylphosphoranylidene)acetate.
10 tert-Alcohol 4 was isolated as a single diastereomer.
11 tert-Alcohol 6 was obtained as a single diastereomer.
12 The reaction carried out at 110 1C gave 6 and 7 (dr 52 : 48) in 3%
and 82% yields, respectively.
13 For the addition of arylrhodium(I) species to nitrile, see:
(a) K. Ueura, T. Satoh and M. Miura, Org. Lett., 2005, 7, 2229;
(b) T. Miura, H. Nakazawa and M. Murakami, Chem. Commun.,
2005, 2855; (c) G. C. Tsui, Q. Glenadel, C. Lau and M. Lautens,
Org. Lett., 2011, 13, 208.
ð3Þ
ð4Þ
c
2990 Chem. Commun., 2012, 48, 2988–2990
This journal is The Royal Society of Chemistry 2012