Rhodium-catalyzed carbonylative skeleton rearrangement of 1,4-enynes tethered by a cyclopropane group

Article abstract of DOI:10.1055/s-0034-1378633

The carbonylative skeleton rearrangement of 1,4 enynes tethered by a cyclopropane group proceeded smoothly in the presence of [Rh(CO)₂Cl]₂ under CO atmosphere to give the corresponding 1,2,4,5,6,7-hexahydrocyclopenta[a]inden-3(3bH)-o

Full text of DOI:10.1055/s-0034-1378633

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▌2311
cluster
Rhodium-Catalyzed Carbonylative Skeleton Rearrangement of 1,4-Enynes
Tethered by a Cyclopropane Group
Carbonylative Skeleton Rearrangement
Gen-Qiang Chen, Xiang-Ying Tang,* Min Shi*
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road,
Shanghai 200032, P. R. of China
Fax +86(21)64166128; E-mail: mshi@mail.sioc.ac.cn
Received: 22.07.2014; Accepted after revision: 24.07.2014
fin unit of 1,4-enyne was a alkylidenecycloalkane, the in-
Abstract: The carbonylative skeleton rearrangement of 1,4 enynes
tramolecular Pauson–Khand reaction and the subsequent
tethered by a cyclopropane group proceeded smoothly in the pres-
aromatization would be inhibited and the reaction may
ence of [Rh(CO)2Cl]2 under CO atmosphere to give the corresponding
take place through a new pathway. Herein, we wish to re-
port an interesting rhodium(I)-catalyzed carbonylative re-
arrangement of 1,4-enynes tethered by a cyclopropane
group.
1,2,4,5,6,7-hexahydrocyclopenta[a]inden-3(3bH)-one derivatives
in moderate yields.
Key words: rhodium(I), carbonylation, skeleton rearrangement,
1,4-enyne, cyclopropane
a) Our Previous Work
R1
Transition-metal-catalyzed carbonylation functions as a
primary and efficient route for introducing carbonyl
groups into an organic molecule.1 The versatility of carbo-
nylation technology has been extended to the formation of
a diverse array of organic carbonyl compounds via reac-
tions of aziridines,2 epoxides,3 oxazolines,4 methylenecy-
clopropanes,5 vinyl cyclopropanes,6,13 spiropentane,7 and
primary alkyl- or arylmethyl halides.8 Some of the carbo-
nylation reactions such as the well-known Monsanto pro-
cess has been commercialized, and CO-free
carbonylations have been also developed.9 Furthermore,
CO can also serve as an one carbon unit for cycloaddi-
tions, including [2+2+1],10 [3+3+1],11 [2+2+2+1],12
[5+2+1],13 etc.
[Rh(CO)2Cl]2, CO
R1
p-xylene, 12 h
OH
R2
R2
O
b) Liu' Work
PtCl2, CO
p-xylene
R
R
c) This Work
[Rh(CO)2Cl]2, CO
?
Transition-metal-catalyzed enyne cycloisomerization has
been studied extensively during the last few decades.
However, only a few examples with regard to 1,4-enynes
have been reported,14 and the carbonylative cycloisomer-
ization of 1,4-enyne was very rare.15 In 2013, we reported
a novel rhodium(I)-catalyzed Pauson–Khand-type reac-
tion of cyclopropane group tethered 1,4-enynes,16 in
which the 1,4-enyne first undergoes an intramolecular
Pauson–Khand reaction and then the subsequent carbon-
ylative cleavage of the spiropentane unit to produce 6-
hydroxy-2,3-dihydro-1H-inden-1-one derivatives in
moderate yields. The ring opening of the cyclopropane
group and the aromatization process comprise the two
driving forces for this reaction to take place (Scheme 1, a).
Liu’s group also reported a novel cycloisomerization of
1,4-enynes in the presence of PtCl2 under CO atmosphere.
The reaction was initiated by a π-alkyne-activated sp3-
hydride shift, a 6-endo-dig cyclization and the subsequent
ring expansion, giving eight-membered carbocycles in
high yields (Scheme 1, b).17 We envisaged that if the ole-
R
R = aryl
Scheme 1 Previous work and this work
We initiated our investigations by seeking the optimal
conditions for the carbonylative skeleton rearrangement
of 1,4-enyne 1a in the presence of transition-metal cata-
lyst, and the results are shown in Table 1. With
Rh(PPh3)3Cl as the catalyst, the corresponding product 2a
was afforded in 29% yield (Table 1, entry 1), and the de-
sired product was not detected when the temperature was
raised to 140 °C (Table 1, entry 2). Using [Rh(CO)2Cl]2 as
the catalyst, the yield of 2a was improved to 46% (Table
1, entry 3). Raising the temperature to 140 °C, the reaction
gave no desired product again (Table 1, entry 4). Other
rhodium
catalysts
such
as
Rh(PPh3)2(CO)Cl,
[Rh(cod)Cl]2, Rh(CO)2(acac), Rh(dppp)2Cl, [Cp*Rh-
Cl2]2, and Rh6(CO)16 were found to be ineffective to cata-
lyze this transformation (Table 1, entries 7–13). Other
transition-metal catalysts such as Ni(cod)2 and Vaska’s
complex were also found to be ineffective in this reaction
(Table 1, entries 14 and 15). [Rh(CO)2Cl]2 was identified
SYNLETT 2014, 25, 2311–2315
Advanced online publication: 21.08.2014
0
9
3
6
-
5
2
1
4
1
4
3
7
-
2
0
9
6
DOI: 10.1055/s-0034-1378633; Art ID: st-2014-s0618-c
© Georg Thieme Verlag Stuttgart · New York

2312
G.-Q. Chen et al.
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to be the best catalyst. When the reactions were carried action by removing a CO ligand from the metal oxidative-
out in other solvents such as PhCl, p-DCB, tetrachlo- ly as carbon dioxide,18 but it was also ineffective to our
roethane, MeCN, and PhCN, the formation of 2a was not reaction. Other additives such as AgSbF6 and phosphine
observed (Table 1, entries 16–20). Addition of NMO has ligands19 (C6F5)3P, DPEphos and dppe have no effect to
been found to be able to accelerate the Pauson–Khand re- improve the yield of 2a (Table 1, entries 21–25). It should
Table 1 Optimization of the Reaction Conditions
O
Ph
catalyst (5 mol%), CO (1 atm)
solvent
Ph
1a
2a
Entrya
Catalyst
Additive
Solvent
Temp (°C)
Yield (%)b
1
2
Rh(PPh3)3Cl
Rh(PPh3)3Cl
[Rh(CO)2Cl]2
[Rh(CO)2Cl]2
[Rh(CO)2Cl]2
[Rh(dppp)(CO)Cl]2
[Rh(cod)Cl]2
Rh(CO)2(acac)
[Rh(C2H4)2Cl]2
Rh(dppp)2Cl
Rh(CO)(PPh3)2Cl
Rh6(CO)16
–
p-xylene
p-xylene
p-xylene
p-xylene
p-xylene
p-xylene
p-xylene
p-xylene
p-xylene
p-xylene
p-xylene
p-xylene
p-xylene
p-xylene
p-xylene
PhCl
100
140
120
140
60–130c
130
100
100
100
100
100
100
100
130
120
120
120
120
80
29
–
n.d.d
46
3
–
4
–
n.d.d
32
5
–
6
–
28
7
–
n.d.d
n.d.d
n.d.d
n.d.d
n.d.d
n.d.d
n.d.d
n.d.d
n.d.d
n.d.d
n.d.d
tracee
n.d.d
n.d.d
n.d.d
n.d.d
n.d.d
n.d.d
tracee
8
–
9
–
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
–
–
–
[Cp*RhCl2]2
Ir(PPh3)2(CO)Cl
Ni(cod)2
–
–
–
[Rh(CO)2Cl]2
[Rh(CO)2Cl]2
[Rh(CO)2Cl]2
[Rh(CO)2Cl]2
[Rh(CO)2Cl]2
[Rh(CO)2Cl]2
[Rh(CO)2Cl]2
[Rh(CO)2Cl]2
[Rh(CO)2Cl]2
[Rh(CO)2Cl]2
–
–
p-DCB
–
tetrachlorethane
MeCN
–
–
PhCN
120
100
100
100
100
120
AgBF4
dppe
p-xylene
p-xylene
p-xylene
p-xylene
p-xylene
NMO
DPEphos
(4-F3CC6H4)3P
a The reaction was performed in a 25 mL flame- and vacuum-dried Schlenk tube. Compound 1 (0.2 mmol) and the catalyst (5 mol%) were added,
and the tube was evacuated and backfilled with CO. Then, the solvent was added, and the reaction mixtures were allowed to stir in an oil bath
at indicated temperature for 12 h.
b Isolated yields.
c The temperature was raised from 60 °C to 130 °C gradually.
d Not detected.
e Detected by the 1H NMR of the crude product.
Synlett 2014, 25, 2311–2315
© Georg Thieme Verlag Stuttgart · New York

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Carbonylative Skeleton Rearrangement
2313
be also noted that when this [Rh(CO)2Cl]2-catalyzed reac-
tion was conducted without CO, the conversion of 1a was
very low (<5%) and only trace amount of product 2a was
afforded.
To evaluate the generality of the reaction, different sub-
strates with varying substituents were synthesized and in-
vestigated under the standard reaction conditions. The
results are shown in Table 2. All of the reactions proceed-
ed smoothly when the substituents were introduced on the
aromatic ring regardless of whether they have electron-
donating or electron-withdrawing substituents (Table 2,
entries 1–10). The structure of 2a was unambiguously
confirmed by the X-ray diffraction (Figure 1).20
Table 2 Substrate Scope of the Carbonylative Skeleton Rearrange-
ment
[Rh(CO)2Cl]2 (5 mol%)
CO (1 atm)
Figure 1 X-ray crystal structure of compound 2a
p-xylene, T (°C), 12 h
O
R
R
1
2
RhI
Entrya
R
Temp (°C)
Yield (%)b
or heat
O
Ph
Ph
O
1
2
1b 4-MeC6H4
1c 3-MeC6H4
1d 3,5-Me2C6H4
1e 4-PhC6H4
1f 4MeOC6H4
1g 4-ClC6H4
120
100
120
120
100
100
120
100
100
100
2b 34
2c 32
2d 34
2e 43
2f 39
2g 30
2h 35
2i 31
2j 32
2k 28
2a'
2a
oxidative
addition
reductive
elimination
Rh(I)
3
Ph
1a
4
5
RhIII
RhIII
6
Ph
7
1h 4-FC6H4
O
C
Ph
A
8
1i 4-AcC6H4
9
1j 4-MeO2CC6H4
1k 4-F3CC6H4
CO
RhIII
10
Ph
a The reaction was performed on 0.2 mmol scale.
b Isolated yields.
B
Scheme 2 A plausible reaction mechanism
The mechanism of this reaction is still unclear at this
stage. A plausible reaction mechanism is shown in
Scheme 2 using 1a as a model substrate.21 Compound 1a
first undergoes oxidative addition in the presence of rho-
dium(I) catalyst to give rhodacyclobutane intermediate A.
The subsequent rearrangement of intermediate A produc-
es intermediate B, which undergoes carbonylation to gen-
erate intermediate C. The reductive elimination in
intermediate C produces compound 2a′. Compound 2a′ is
a relatively labile substance, which can easily produce 2a
via 1,2-alkyl migration.22
penta[a]inden-3(3bH)-one derivatives in moderate yields.
A plausible reaction mechanism has also been proposed.
General Procedure for the Rhodium-Catalyzed Carbonylative
Skeleton Rearrangement
To a 25 mL flame- and vacuum-dried Schlenk tube were added the
substrate 1 (0.2 mmol) and [Rh(CO)2Cl]2 (0.005 mmol). The
Schlenk tube was evacuated and backfilled with CO, then p-xylene
(2 mL) was added, and the reaction mixture was allowed to stir at
indicated temperature for 12 h. The product was purified by column
chromatography or preparative silica gel plate using PE and EtOAc
as eluent (PE–EtOAc = 8:1).
In summary, we have developed a novel carbonylative
skeleton rearrangement of cyclopropane-tethered 1,4-
enynes catalyzed by [Rh(CO)2Cl]2 under CO atmosphere,
affording the corresponding 1,2,4,5,6,7-hexahydrocyclo-
Compound 2a
A white solid; mp 104–107 °C. 1H NMR (400 MHz, CDCl3, TMS):
δ = 1.13–1.17 (m, 1 H, CH2), 1.20–1.30 (m, 2 H, CH2), 1.56–1.58
© Georg Thieme Verlag Stuttgart · New York
Synlett 2014, 25, 2311–2315

2314
G.-Q. Chen et al.
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(m, 1 H, CH2), 1.965–1.973 (m, 1 H, CH2), 2.36–2.37 (m, 1 H,
CH2), 2.63–2.71 (m, 4 H, CH2), 2.76–2.81 (m, 1 H, CH2), 3.10–3.14
(m, 1 H, CH2), 6.36 (d, J = 1.5 Hz, 1 H, Ar), 7.18–7.21 (m, 1 H, Ar),
7.26–7.28 (m, 4 H, Ar). 13C NMR (100 MHz, CDCl3, TMS): δ =
21.3, 23.9, 29.0, 29.6, 36.3, 40.8, 56.9, 122.4, 126.5, 127.1, 128.6,
138.2, 155.7, 173.2, 181.6, 197.8. IR (CH2Cl2): ν = 2950, 1720,
1604, 1435, 1275, 1107, 858, 765, 750, 698 cm–1. MS (%): m/e (%)
= 250 (48.56) [M+], 222 (12.62), 208 (100.00), 193 (17.25), 179
(34.08), 165 (42.13), 152 (13.64), 128 (13.34), 115 (26.15), 89
(11.25). HRMS (EI): m/z calcd for C18H18O: 250.1358; found:
250.1357.
(7) Matsuda, T.; Tsuboi, T.; Murakami, M. J. Am. Chem. Soc.
2007, 129, 12596.
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Knox, G. R.; Pauson, P. L.; Watts, W. E. J. Chem. Soc.,
Perkin Trans. 1 1973, 1, 977.
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Compound 2b
A white solid; mp 123–125 °C. 1H NMR (400 MHz, CDCl3, TMS):
δ = 1.15–1.19 (m, 1 H, CH2), 1.26–1.34 (m, 2 H, CH2), 1.55–1.56
(m, 1 H, CH2), 1.69–1.75 (m, 1 H, CH2), 1.93–1.98 (m, 1 H, CH2),
2.29 (s, 3 H, CH3), 2.33–2.40 (m, 1 H, CH2), 2.59–2.75 (m, 4 H, 2
CH2), 2.77 (d, J = 13.6 Hz, 1 H, CH2), 3.09 (dd, J1 = 13.6 Hz, J2 =
2.0 Hz, 1 H, CH2), 6.35 (d, J = 1.6 Hz, 1 H, =CH), 7.09 (d, J = 8.0
Hz, 2 H, Ar), 7.17 (d, J = 8.0 Hz, 2 H, Ar). 13C NMR (100 MHz,
CDCl3, TMS): δ = 21.0, 21.3, 23.9, 28.9, 29.6, 36.2, 40.9, 56.6,
122.3, 126.9, 129.3, 135.1, 136.1, 155.9, 173.4, 181.5, 197.9. IR
(CH2Cl2): ν = 2930, 2856, 1674, 1541, 1386, 1327, 1054, 846, 730
cm–1. MS: m/e (%) = 264 (58.45) [M+], 236 (17.47), 222 (100.00),
207 (33.57), 193 (21.75), 179 (33.86), 165 (21.79), 128 (11.00), 115
(20.07), 89 (18.94). HRMS (EI): m/z calcd for C19H20O: 264.1514;
found: 264.1513.
(13) (a) Wender, P. A.; Gamber, G. G.; Hubbard, R. D.; Zhang,
L. J. Am. Chem. Soc. 2002, 124, 2876. (b) Wang, Y.; Wang,
J.; Su, J.; Huang, F.; Jiao, L.; Liang, Y.; Yang, D.; Zhang, S.;
Wender, P. A.; Yu, Z.-X. J. Am. Chem. Soc. 2007, 129,
10060.
Acknowledgment
(14) For transition-metal-catalyzed cyclizations of 1,4-enynes,
see: (a) Shi, X.; Gorin, D. J.; Toste, F. D. J. Am. Chem. Soc.
2005, 127, 5802. (b) Buzas, A.; Gagosz, F. J. Am. Chem.
Soc. 2006, 128, 12614. (c) Marion, N.; Diez-Gonzalez, S.;
De Fremont, P.; Noble, A. R.; Nolan, S. P. Angew. Chem.
Int. Ed. 2006, 45, 3647. (d) Shu, X.; Schienebeck, C. M.;
Song, W.; Guzei, I. A.; Tang, W. Angew. Chem. Int. Ed.
2013, 52, 13601. (e) Schienebeck, C. M.; Robichaux, P. J.;
Li, X.; Chen, L.; Tang, W. Chem. Commun. 2013, 49, 2616.
(f) Xu, X.; Liu, P.; Shu, X.; Tang, W.; Houk, K. N. J. Am.
Chem. Soc. 2013, 135, 9271. (g) Shu, X.; Li, X.; Shu, D.;
Huang, S.; Schienebeck, C. M.; Zhou, X.; Robichaux, P. J.;
Tang, W. J. Am. Chem. Soc. 2012, 134, 5211. (h) Shu, X.;
Huang, S.; Shu, D.; Guzei, I. A.; Tang, W. Angew. Chem.
Int. Ed. 2011, 50, 8153.
(15) For carbonylative cycloisomerisation of 1,4-enynes, see:
(a) Fukuyama, T.; Ohta, Y.; Brancour, C.; Miyagawa, K.;
Ryu, I.; Dhimane, A.-L.; Fensterbank, L.; Malacria, M.
Chem. Eur. J. 2012, 18, 7243. (b) Li, X.; Song, W.; Tang, W.
J. Am. Chem. Soc. 2013, 135, 16797. (c) Li, X.; Huang, S.;
Schienebeck, C. M.; Shu, D.; Tang, W. Org. Lett. 2012, 14,
1584.
We thank the Shanghai Municipal Committee of Science and Tech-
nology (11JC1402600), the National Basic Research Program of
China (973)-2010CB833302, and the National Natural Science
Foundation of China (20472096, 21372241, 21361140350,
20672127, 21102166, 21121062, 21302203 and 20732008).
Supporting Information for this article is available online
at
http://www.thieme-connect.com/products/ejournals/journal/
10.1055/s-00000083.SunpfgIpi
o
o
nr
i
References and Notes
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(19) It has been reported that electron-deficient CO or phosphine
ligands were critical to increase the π-acidity of the rhodium
center, see: (a) Huang, S.; Li, X.; Lin, C. L.; Guzeic, I. A.;
Tang, W. Chem. Commun. 2012, 48, 2204. (b) Shu, X.-Z.;
Shu, D.; Schienebeck, C. M.; Tang, W. Chem. Soc. Rev.
2012, 41, 7698. Phosphine ligands have great influence on
Synlett 2014, 25, 2311–2315
© Georg Thieme Verlag Stuttgart · New York

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rhodium-catalyzed carbonylation and decarbonylation and a
Carbonylative Skeleton Rearrangement
2315
RhI
π-acidic phosphine ligand can promote decarbonylation in
some cases, see: (c) Chen, P.-H.; Xu, T.; Dong, G. Angew.
Chem. Int. Ed. 2014, 53, 1674. (d) Xu, T.; Savage, N. A.;
Dong, G. Angew. Chem. Int. Ed. 2014, 53, 1891; however,
concerning about that phosphine ligands have no effect in
our current reaction, the reason is still not clear at the present
stage.
or heat
Ph
O
Ph
O
2a
2a'
RhI
1a
RhI
Ph
(20) The crystal data of 2a have been deposited in CCDC with
number 906119.
(21) There is still another mechanism that can explain the
formation of product 2a. However, this mechanism involves
the formation of a very strained intermediate, which makes
this mechanism seems less possible (Scheme 3).
(22) For a similar migration at cyclopentadiene ring, see:
(a) Replogle, K. S.; Carpenter, B. K. J. Am. Chem. Soc.
1984, 106, 5751. (b) Li, Z.; Vasella, A. Helv. Chim. Acta
1996, 79, 2201. (c) Ye, B.; Cramer, N. J. Am. Chem. Soc.
2013, 135, 636.
O
RhIII
Ph
Ph
RhI
CO
RhIII
Ph
Ph
RhI
RhIII
Ph
or
RhIII
Ph
Scheme 3
© Georg Thieme Verlag Stuttgart · New York
Synlett 2014, 25, 2311–2315

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