Rapid access to cyclopentadiene derivatives through gold-catalyzed cycloisomerization of ynamides with cyclopropenes by preferential activation of alkenes over alkynes

Article abstract of DOI:10.1039/c7cc01368j

In this communication, gold-catalyzed intermolecular cycloisomerization of cyclopropenes and ynamides is investigated. The current transformation displayed an activation priority of double bonds over triple bonds by the cationic gold catalyst, giving the corresponding cyclopentadienes in good to excellent yields. Additionally, this protocol can be expanded to a one-pot two-step procedure for the synthesis of substituted cyclopentanones.

Full text of DOI:10.1039/c7cc01368j

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Marilyn M. Olmstead, Alan L. Balch, Josep M. Poblet, Luis Echegoyenet al.
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DOI: 10.1039/C7CC01368J
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Rapid Access to Cyclopentadienes Derivatives through Gold‐
Catalyzed Cycloisomerization of Ynamides with Cyclopropenes by
Preferential Activation of Alkene over Alkyne
Received 00th January 20xx,
Accepted 00th January 20xx
Xing Cheng,†a,b Lei Zhu,†a Meijun Lin,a,b Jianxin Chen,*b and Xueliang Huang*a
DOI: 10.1039/x0xx00000x
www.rsc.org/
In this communication, the gold‐catalyzed intermolecular
cycloisomerization of cyclopropenes and ynamides is investigated.
The current transformation displayed an activation priority of
double bond over triple bond by the cationic gold catalyst, giving
the corresponding cyclopentadienes in good to excellent yields.
Additionally, this protocol can be expanded to a one‐pot two‐step
procedure for the synthesis of substituted cyclopentones.
Previous works: activation of triple bond
R1
R4
R3
R2
[Au]
[Au]
+
(a)
(b)
R3
R4
R1
Ar
R2
nucleophilic
R
N
+
N
R'
R
Gold‐catalyzed cycloisomerization of enynes has received
considerable attention in the past decades.1,2 The state‐of‐art
of this strategy has been showcased by construction of
complex molecules from simple building blocks in highly
efficient and atom economical fashion. Generally, the cationic
gold catalyst would preferentially activate the alkyne moiety
instead of the alkenyl tether. Hence, in absence of additional
nucleophiles, nucleophilic addition of the alkene to the
activated alkyne would take place selectively. Similar priority
has also been displayed by gold‐catalyzed intermolecular
reaction of alkenes with alkynes. For example, Echavarren has
implemented an elegant approach to cyclobutenes via gold‐
catalyzed intermolecular [2+2] cycloaddition of simple alkenes
and alkynes (Scheme 1a).3 More recently, Liu and co‐workers
reported intermolecular reaction of ynamides4 with alkenes
(Scheme 1b).5 Liu6 and we7 have concurrently reported gold‐
catalyzed intermolecular nitrene transfer8 from 2H‐azirines to
ynamides. As a carbo‐variant of 2H‐azirine, cyclopropene also
possesses high strain energy, and ready for ring opening under
mild conditions.9 In connection to our interest in gold‐
catalyzed annulation,7,10 we were curious about the reactivity
of cyclopropene towards ynamide under gold catalysis. In 2010,
Wang and co‐workers have disclosed a regioselective synthesis
nucleophilic
[Au]
R3
R1
R1
R3
H
H
(c)
R4
R2
R2
R4
R4
R4
nucleophilic
This work: activation of double bond
R1 R2
R3
N
R3
N
(d)
+
R2
[Au]
nucleophilic
R1
Scheme 1. Examples on gold catalyzed enyne
cycloisomerizations.
of benzene derivatives (Scheme 1c).11 Intriguingly, they have
also observed the preferential activation of alkynyl moiety
over the strained alkene (cyclopropene) by a gold catalyst.
Despite of these elegant achievements, to our knowledge,
gold‐catalyzed intermolecular reaction of alkyne with
cyclopropene has never been realized before.12 Below, we
describe our recent efforts, which led to the newly discovered
activation priority of alkene over alkyne by cationic gold
catalyst. Guided by this reaction mode, substituted
cyclopentadiene derivatives were synthesized in an atom
economic fashion (Scheme 1d).
By taken advantage of the ambivalent nature of ynamide,
Gagosz and Skrydstrup have developed a rare approach to
substituted cyclopentadiene via the dimerization of the
corresponding alkyne.13 For the gold‐catalyzed reaction of
ynamides with propargylic carboxylates, Hashmi and co‐
workers have found that the dimerization of ynamides were
completely suppressed once carbenoid intermediate was
generated, giving cyclopentadienes exclusively.14 It is
a. Key Laboratory of Coal to Ethylene Glycol and Its Related Technology, Fujian
Institute of Research on the Structure of Matter, Chinese Academy of Sciences,
Fuzhou, Fujian 350002, P. R. China. E‐mail: huangxl@fjirsm.ac.cn. Web:
http://www.fjirsm.cas.cn/huangxl/.
b. College of Chemistry and Chemical Engineering, Fujian Normal University, Fuzhou,
Fujian 350007, P. R. China. E‐mail: jxchen@fjnu.edu.cn.
† These authors contributed equally to this work.
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1‐3 | 1
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worthwhile to mention that the ynamides employed in these gold catalyst bearing an N‐heterocyclic carbeneVileiwgaAnrtidcl,e Ownilitnhe
two cases displayed relatively limited substrate scope. The respect of both reaction time and theDOisIo: 1la0t.1e0d39y/Cie7lCdC0o1f3638aJ
current method complements studies of Gagosz, Skrydstrup (entry 7). Control experiments highlighted the critical role of
and Hashmi. Compared with the intramolecular reaction of the cationic nature of gold catalyst (entries 8 and 9). Switching
cyclopropene and alkyne reported by Wang,11 this study the reaction media to DCE (1,2‐dichloroethane) or acetonitrile,
showed reverse activation priority of cyclopropene over alkyne resulted in a slightly shorter reaction time, while similar yields
by gold catalyst, even though ynamide is generally considered were maintained (entries 10 and 11). We have also tried to
to be more reactive than normal internal alkyne.
examine other reaction parameters to enhance the selectivity
and the yield of 4a, however no positive effects were obtained
thus far.17
Table 1. Substrates scope with respects to a variety of
[a]
triazoles 2.
O
Table 2. Scope of Ynamides 1 .
with Cyclopropene 2a [a]
Ph
O
O
Ph
Me
catalyst (5 mol%)
N
O
R1
+
Ph
N
DCM (1 mL), 100 oC, Ar
Ph
N
IPrAuNCPhSbF6 (5 mol%)
CH3CN (1 mL), 100 o
Ph
Me
R1
N
+
Me
3a
C
Ph
, 0.2 mmol
1a
, 1.0 mmol
2a
catalyst
Me
3a-o
(%)[a]
(%)[a]
entry
time (h)
4a
3a
0.2 mmol
1,
2a, 1.0 mmol
1
2
JohnPhosAu(MeCN)SbF6
tBuXPhosAu(MeCN)SbF6
1
4
47
25
Cl
3a, R = H, 1 h, 98%
R
trace
35
--
Cl
3b, R = Me, 1 h, 97%
3c, R = Et, 1 h, 99%
PPh3AuNTf2
2
3
3
4
70
62
O
O
(4-CF3C6H5)3PAuNTf2
--
O
3d, R = OMe, 1.5 h, 99%
3e, R = F, 1.5 h, 95%
3f, R = Cl, 1 h, 99%
O
N
IMesAuCl/AgNTf2
IAdAu(PhCN)SbF6
IPrAu(PhCN)SbF6
IPrAuCl
5
6
7
8
9
2
22
2.5
50
60
82
61
--
--
--
N
Me
N
O
Me
Ph
O
Ph
Ph
97
3k, 2 h, 84%
Me
3j, 1.5 h, 85%
3g
, R = Br, 1.5 h, 93%
NR
AgSbF6
trace
10[b]
11[c]
--
--
IPrAu(PhCN)SbF6
IPrAu(PhCN)SbF6
1
1
98
95
O
O
O
O
O
N
N
N
PtBu2
R
Ph
Me
O
O
O
Ph
Ph
N
N
N
R
R
R
Me
Me
R
3l, 1.5 h, 94%
3h, 1.5 h, 93%
3i, 2 h, 95%
JohnPhos: R = H
tBuXPhos: R = isopropyl
IMes: R = 2,4,6-trimethylphenyl
IPr: R = 2,6-diisopropylphenyl
IAd: R = adamantyl
4a
S
O
Ph
Ms
Ph
O
O
N
N
Me
N
Me
O
Ph
Ph
[a] Isolated yield. [b] CH3CN was selected as solvent
instead of DCM. [c] DCE was selected as solvent instead of
DCM.
Ph
Me
Me
3m, 1 h, 70%
3o, 7 h, 56%
3n, 2 h, 48%
We began our study using readily available ynamide 1a and
cyclopropene 2a as the model substrates (Table 1). To test the
reactivity of 1a towards cyclopopene 2a, we first examined the
[a] [1] = 0.2 M , yields were referred to pure products
upon isolation after column chromatography on silica gel.
This new method proved to be versatile, as a wide array of
ynamides could participate in current transformation, and the
results were shown in Table 2. Specifically, a series of
ynamides featuring both electron‐donating (methyl, ethyl and
activity
of
the
Echavarren’s
catalyst
[JohnPhosAu(MeCN)SbF6]15 which has been proved to be
active catalyst in our previous reaction of ynamides and 2H‐
azirines.7 As depicted, when the reaction was carried out in
methoxy, 3b
bromo, 3e 3g) groups at the para position of the phenyl ring
‐3d) and electron‐withdrawing (fluoro, chloro, and
o
dichloromethane (DCM) at 100 C for 1h, multi‐substituted
‐
cyclopentadiene 3a was isolated in 47% yield. Together with
3a, dihydronaphthalene 4a was also obtained in 25% yield
(entry 1). Of note, the products resulting from dimerization of
1a13 were not observed. Because of self‐reaction, an excess of
2a was required. These reaction outcomes may indicate a
were well tolerable under the standard conditions, providing
the desired products in good to excellent yields (84‐99%). The
ynamides containing chloro group at the meta and ortho
position of the phenyl ring reacted well with 2a, affording the
corresponding cyclopentadienes (cf. 3j and 3k) in high yields
(85% and 84%). 1‐naphthyl, and 2‐naphthyl substituted
ynamides were viable substrates as well, leading to the
formation of desired product 3h and 3i in excellent yields (93%
and 95%). Interestingly, the ynamides derived from hex‐1‐yne
and ethynylcyclopropane (1l and 1m) were also amenable to
this reaction. Compound 3l and 3m were obtained in 94% and
70% yields, respectively. In addition, the reaction of ynamide
derived from thienyl acetylene (1n) took place well (cf. 3n).
Replacing the oxazolidinone moiety with a sulfonamide group,
preferential coordination of cyclopropene 2a over ynamide 1a
.
The structure of 3a was further confirmed by single‐crystal X‐
ray analysis. When a catalyst bearing a more bulky ligand
(tBuXPhos) was employed, longer reaction time was required.
Although 4a was isolated in slightly higher yield, there was
only trace of 3a could be observed from the reaction mixture
(entry 2). Pleasingly, the reaction catalyzed by Gagosz’s
catalyst (Ph3PAuNTf2)16 led to a selective formation 3a, which
was obtained in 70% yield upon isolation (entry 3). Further
screening of the catalysts led to the best choice of the cationic
2 | J. Name., 2012, 00, 1‐3
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resulted in
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a
lower reaction rate, and corresponding enamide triggered ring opening of
C
, followed by the
View Article Online
DOI: 10.1039/C7CC01368J
cyclopentadiene 3o was obtained with 56% yield.
intramolecular ring closure of D was also reasonable. Addition
[a]
Table 3. Scope of Cyclopropene with Ynamides 1a
2
.
[a] Cyclopropene 2b was added in four portions (0.5
mmol/0.5 h), after the addition, the reaction was heated
for one more hour. [b] Cyclopropene 2h (1 mmol, 5 equiv)
o
was added, after stirred at 100 C for one hour, another
portion of 2h (0.4 mmol, 2 equiv) was added, then the
reaction was heated for half an hour.
Subsequently, with the ynamide 1a as the model
nucleophile, an array of cyclopropenes
standard conditions. As the results depicted in Scheme 3, by
variation of R2 in cyclopropene
, electron‐donating groups
(methyl) and electron‐withdrawing (chloro, and bromo) groups
setting at the para position of the phenyl ring had negligible
effects on the reactions, and all cyclopropenes reacted
2 were tested under
2
Scheme 2. Mechanism rationale.
of styrene to the reaction mixture gave cyclopropane
5
as the
major product (Scheme 3).20 The formation of
5 provides
evidence for the generation of carbene intermediate
Because of the observed regioselective of cyclopentadiene
3a vs 3‘), the reaction pathway initiated by activation of
A.
3
smoothly with ynamide 1a
cyclopentadienes in 71%‐99% yields (cf. 3q
,
giving the corresponding
3r and 3s).
,
(
Similarly, cyclopropenes containing trifluoromenthyl or chloro
group at the meta position of the phenyl ring exhibited good
reactivity as well, affording the desired cyclopentadienes in
excellent yields (cf. 3t and 3u). Moreover, cyclopropene 2v
bearing steric hindered group (otho‐chlorophenyl) could also
react with 1a equally well, leading to formation of 3v in 90%
yield upon isolation. 2‐Naphthyl, methyl and dialkyl
substituted cyclopropenes (2w and 2x) could react with
ynamide 1a, furnishing cyclopentadienes 3w and 3x in 80%
and 81% yields, respectively.
ynamide could be ruled out (path b). Under certain conditions,
a 1,4‐hydride migration of
phenyl‐substituted 1,3‐diene
A
might take place, furnishing
I
, which could further serve as a
two‐carbon unit to participate in Liu’s [4+2] cycloaddition with
ynamide 1a,5 and eventually gave dihydronaphthalene 4a
(path c).
From mechanistic point of view,18 two reaction pathways
based on distinct activation piority of the
π bond systems
could be proprosed (Scheme 2). Activation of cyclopropene 2a
(path a) by cationic gold catalyst would furnish vinyl carbenoid
Scheme 3. Mechanistic experiment.
The enamide moiety in
3 has offered a useful synthetic
intermediate
of ynamide, addition of 1a to intermediate
A
. By taking advantage of the nucleophilic nature
would give
handle for downstream manipulation. After brief condition
optimization, 3a could be transformed to substituted
A
B.
Intramolecular cyclization of allylic gold moiety to the most
electrophilic carbon center results in the formation of the final
product 3a and with concomitant regeneration of the gold
cyclopentenone
to mention that when the reaction was carried out on 0.5
mmol scale, the amount of cyclopropene could be decreased
to equiv. without sacrifising the reaction outcome.
Encouraged by this result, we sought to develop a one‐pot
two‐step procedure for the direct preparation of . Pleasingly,
6 after simple acidic workup. It is worthwhile
2
catalyst. Although efforts to isolate transient cyclopropene
were not successful thus far, an alternative mechanistic
pathway going through cyclopropenation of ynamide 1a 19
C
3
,
6
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with furans, see: f) A. S. K. Hashmi, T. M. Frost aVniedwJA.rtWicle. BOnaltinse,
when the gold‐catalyzed formal [3+2] cycloaddition were
complete, without the isolation of 3, treatment of the reaction
J. Am. Chem. Soc. 2000, 122, 11553. g) A. S. K. Hashmi, T. M.
DOI: 10.1039/C7CC01368J
Frost and J. W. Bats, Org. Lett. 2001, 3, 3769. h) N. Huguet, D.
Lebœuf, and A. M. Echavarren, Chem. Eur. J. 2013, 19, 6581.
(a) V. López‐Carrillo and A, M. Echavarren, J. Am. Chem. Soc.
2010, 132, 9292. b) E. de Orbe and A. M. Echavarren, Org.
Synth. 2016, 93, 115.
For representative reviews on ynamides, see: a) K. A.
DeKorver, H. Li, A. G. Lohse, R. Hayashi, Z. Lu, Y. Zhang and R.
P. Hsung, Chem. Rev. 2010, 110, 5064. b) G. Evano, A. Coste
and K. Jouvin, Angew. Chem. Int. Ed. 2010, 49, 2840. c) G.
Evano, K. Jouvin and A. Coste, Synthesis 2013, 45, 17. d) X.‐N.
Wang, H.‐S. Yeom, L.‐C. Fang, S. He, Z.‐X. Ma, B. L. Kedrowski
and R. P. Hsung, Acc. Chem. Res. 2014, 47, 560. e) G. Evano,
C. Theunissen and M. Lecomte, Aldrichimica Acta 2015, 48,
59. For selected examples on the synthesis of ynamides, see:
f) C. A. Zificsak, J. A. Mulder, R. P. Hsung, C. Rameshkumar
and L.‐L. Wei, Tetrahedron, 2001, 57, 7575. g) T. Hamada, X.
Ye and S. S. Stahl, J. Am. Chem. Soc. 2008, 130, 833. h) S. N.
mixture with 8 equiv of concentrated HCl aq., and heating for 3
h at 100 oC, a variety of cyclopentenones
in a straightforward manner (Table 4).
6 could be prepared
3
4
Table 4. One‐pot synthesis of cyclopentenones 6.
Karad, S. Bhunia and R.‐S. Liu, Angew. Chem. Int. Ed. 2012
,
51, 8722.
5
6
R. B. Dateer, B. S. Shaibu and R.‐S. Liu, Angew. Chem. Int. Ed.
2012, 51, 113.
S. K. Pawar, R. L. Sahani and R.‐S. Liu, Chem. Eur. J. 2015, 21,
10843.
7
8
L. Zhu, Y. Yu, Z. Mao and X. Huang, Org. Lett. 2015, 17, 30.
For elegant review on this topic, and references cited therein:
P. W. Davies and M. Garzon, Asian J. Org. Chem. 2015, 4, 694.
For recent selected reviews, see: a) M. S. Baird, Chem. Rev.
2003, 103, 1271. b) M. Rubin, M. Rubina and V. Gevorgyan,
Chem. Rev. 2007, 107, 3117. c) I. Marek, S. Simaan and A.
Masarwa, Angew. Chem. Int. Ed. 2007, 46, 7364. d) Z.‐B. Zhu,
Y. Wei, M. Shi, Chem. Soc. Rev., 2011, 40, 5534. e) B.‐L. Lu, L.
Dai, M. Shi, Chem. Soc. Rev., 2012, 41, 3318. f) A.
Archambeau, F. Miege, C. Meyer and J. Cossy, Acc. Chem.
Res. 2015, 48, 1021. g) C. Song, J. Wang and Z. Xu, Acta Chim.
Sinica, 2015, 73, 1114.
In summary, we have described the first gold‐catalyzed
intermolecular cycloisomerizaition of ynamides with
cyclopropenes, furnishing polysubstituted cyclopentadienes in
good to excellent yields. Compared with previous gold‐
catalyzed enyne cycloisomerization, the current work
represents a rare example on activation priority of alkenes
over alkynes under gold catalysis.21
9
10 a) Y. Wu, L. Zhu, Y. Yu, X. Luo and X. Huang, J. Org. Chem.
2015, 80, 11407. b) Y. Yu, G. Chen, L. Zhu, Y. Liao, Y. Wu and
X. Huang, J. Org. Chem. 2016, 81, 8142.
Acknowledgements
We thank the financial support by NSFC (Grant No. 21402197, 11 C. Li, Y. Zeng, H. Zhang, J. Feng, Y. Zhang and J. Wang, Angew.
Chem. Int. Ed. 2010, 49, 6413.
21502190), NSF of Fujian (Grant No. 2015J05043), Hundred‐
Talent Program and the Strategic Priority Research Program of
the Chinese Academy of Sciences (Grant No. XDB20000000).
12 a) A. Padwa and S. L. Xu, J. Am. Chem. Soc. 1992, 114, 5881.
b) J. Yin and J. D. Chisholm, Chem. Commun. 2006, 632. c) A.
Tenaglia, K. Le Jeune, L. Giordano and G. Buono, Org. Lett.
2011, 13, 636. d) H. Zhang, B. Wang, H. Yi, Y. Zhang and J.
Wang, Org. Lett. 2015, 17, 3322.
Notes and references
13 S. Kramer, Y. Odabachian, J. Overgaard, M. Rottländer, F.
Gagosz and T. Skrydstrup, Angew. Chem. Int. Ed. 2011, 50,
5090.
14 E. Rettenmeier, A. M. Schuster, M. Rudolph, F. Rominger, C.
A. Gade and A. S. K. Hashmi, Angew. Chem. Int. Ed. 2013, 52,
5880.
15 C. Nieto‐Oberhuber, S. López, M. P. Muñoz, D. J. Cárdenas, E.
Buñuel, C. Nevado and A. M. Echavarren, Angew. Chem. Int.
Ed. 2005, 44, 6146.
16 N. Mézailles, L. Ricard and F. Gagosz, Org. Lett. 2005, 7, 4133.
17 See ESI for more details on condition experiments.
18 A. S. K. Hashmi, Angew. Chem. Int. Ed. 2010, 49, 5232.
19 J. F. Briones and H. M. L. Davies, J. Am. Chem. Soc. 2012, 134,
11916.
20 M. J. González, J. González, L. A. Lýpez and R. Vicente, Angew.
Chem. Int. Ed. 2015, 54, 12139.
21 a) J. Schießl, M. Rudolph and A. S. K. Hashmi, Adv. Synth.
Catal. 2017, 359, 639. b) A. H. Bagi, Y. Khaledi, H. Ghari, S.
Arndt, A. S. K. Hashmi, B. F. Yates and A. Ariafard, J. Am.
Chem. Soc. 2016, 138, 14599.
1
For recent reviews on gold catalysis, see: a) A. Fürstner and P.
W. Davies, Angew. Chem. Int. Ed. 2007, 46, 3410. b) A. S. K.
Hashmi, Chem. Rev. 2007, 107, 3180. c) C. M. Friend and A. S.
K. Hashmi, Acc. Chem. Res. 2014, 47, 729. d) D. Qian and J.
Zhang, Chem. Soc. Rev. 2015, 44, 677. e) Z. Zheng, Z. Wang, Y.
Wang and L. Zhang, Chem. Soc. Rev. 2016, 45, 4448. f) W. Zi
and F. D. Toste, Chem. Soc. Rev. 2016, 45, 4567. g) D. B.
Huple, S. Ghorpade and R.‐S. Liu, Adv. Synth. Catal. 2016
,
358, 1348. h) D. Pflästerer and A. S. K. Hashmi, Chem. Soc.
Rev. 2016, 45, 1331. i) L. Liu and J. Zhang, Chem. Soc. Rev.
2016, 45, 506.
2
For selected reviews on enyne cycloisomerization, see: a) E.
Jiménez‐Núñez and A. M. Echavarren, Chem. Rev. 2008, 108,
3326. b) C. Obradors and A. M. Echavarren, Acc. Chem. Res.
2014, 47, 902. c) R. Dorel and A. M. Echavarren, Chem. Rev.
2015, 115, 9028. For recent examples, see: d) J. Carreras, M.
Livendahl, P. R. McGonigal and A. M. Echavarren, Angew.
Chem. Int. Ed. 2014, 53, 4896. e) J. Carreras, M. S. Kirillova
and A. M. Echavarren, Angew. Chem. Int. Ed. 2016, 55, 7121.
Selected examples on gold‐catalyzed reactions of alkynes
4 | J. Name., 2012, 00, 1‐3
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