Calcium carbide as the acetylide source: Transition-metal-free synthesis of substituted pyrazoles via [1,5]-sigmatropic rearrangements

Article abstract of DOI:10.1039/c6gc02776h

Under transition-metal-free conditions, calcium carbide was used as the acetylide source to react with a wide range of N-tosylhydrazones derived from aldehydes or ketones, affording various substituted pyrazoles in good yields with high regioselectivities. The transformations go through [3 + 2] cycloadditions followed by [1,5]-sigmatropic rearrangements, which are supported by deuterium-labeling experiments.

Full text of DOI:10.1039/c6gc02776h

View Article Online
View Journal
Green
Chemistry
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: H. Jiang, Y. Yu, W.
Huang, Y. Chen, B. Gao and W. Wu, Green Chem., 2016, DOI: 10.1039/C6GC02776H.
This is an Accepted Manuscript, which has been through the
Volume 18 Number
7 7 April 2016 Pages 1821–2242
Royal Society of Chemistry peer review process and has been
accepted for publication.
Green
Chemistry
Accepted Manuscripts are published online shortly after
Cutting-edge research for a greener sustainable future
www.rsc.org/greenchem
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1463-9262
CRITICAL REVIEW
G. Chatel et al.
Heterogeneous catalytic oxidation for lignin valorization into valuable
chemicals: what results? What limitations? What trends?
rsc.li/green-chem

Page 1 of 6
Green Chemistry
View Article Online
DOI: 10.1039/C6GC02776H
Journal Name
RSCPublishing
COMMUNICATION
Calcium Carbide as the Acetylide Source: Transition-
Metal-Free Synthesis of Substituted Pyrazoles via [1,5]-
Sigmatropic Rearrangements†
Received 00th January 2012,
Accepted 00th January 2012
DOI: 10.1039/x0xx00000x
Yue Yu, Wei Huang, Yang Chen, Bingjie Gao, Wanqing Wu* and Huanfeng Jiang*
www.rsc.org/greenchem
amounts of water. These few reported methods can be divided into
two categories according to the reaction results (Scheme 1). For one
of them, the acetylide anion derived from calcium carbide undergoes
an electrophilic addition to its triple bond for the synthesis of C=Cꢀ
containing compounds, such as enaminones2, vinyl ethers3 and
pyrroles4. The other kind of reaction is that the acetylide anion acts
Under transition-metal-free conditions, calcium carbide was
used as the acetylide source to react with a wide range of N-
tosylhydrazones derived from aldehydes or ketones, affording
various substituted pyrazoles in good yields with high
regioselectivities. The transformations go through [3+2]
cycloadditions followed by [1,5]-sigmatropic rearrangements,
which are supported by deuterium-labeling experiments.
as
a nucleophile under suitable conditions and attack the
electrophilic aryl or carbonyl carbons, leading to the formation of
various acetylide molecules, such as diarylethynes,5 propargyl
alcohols6 and propargyl amines7. However, the development of
alternative approaches for the direct use of calcium carbide to
synthesize other practical acetylene derivatives is still very
imperative.
Introduction
The most suitable type of organic reactions for connecting scientific
study to industrial manufacture should be in line with four principles:
(i) starting with simple, inexpensive and easyꢀtoꢀget molecules; (ii)
proceeding in mild and safe conditions; (iii) having atomꢀeconomy
and stepꢀeconomy; (iv) obtaining valuable products.1 Taking as an
example, calcium carbide (CaC2) was prepared from an electric
smelting furnace of coal and calcium oxide in industrial production,
which has become an important basic organic chemical raw material
for the manufacture of acetylene and calcium cyanamide. As a main
source of the simplest alkyne, solid calcium carbide is a promising
candidate for a safer and cheaper alternative to acetylene gas, for the
production of acetylene derived chemicals. Up to date, there have
been few reports of utilizing CaC2 directly in organic synthesis due
to its insolubility in common organic solvents, which was derived
from its highly stable lattice structure.2ꢀ7 Fortunately, polar aprotic
solvents such as DMSO were found to be good solvents for CaC2
with the addition of equivalent amount of base and controlled
Scheme 1. Synthesis of various commodity chemicals by using calcium carbide as
the acetylene source
Pyrazole is one of the most valuable compounds that can be easily
obtained from acetylene. As an important class of heterocyclic ring
systems, pyrazole derivatives are core frameworks of many
biologically active molecules and drug intermediates.8 Selected
pharmaceutical and agromedical examples include Celebrex, Viagra,
Acomplia, Fenpyroximate and Tebufenpyrad.9 The syntheses of
pyrazoles have received considerable attention and numerous
approaches have been developed in past decades, including the
classical condensations of hydrazines with 1,3ꢀdicarbonyl
Key Laboratory of Functional Molecular Engineering of Guangdong Province,
School of Chemistry and Chemical Engineering, South China University of
Technology, Guangzhou 510640 (China). E-mail: cewuwq@scut.edu.cn,
jianghf@scut.edu.cn
†
Electronic Supplementary Information (ESI) available: See DOI: 10.1039/
compounds10,
the
dipolar
[3+2]
cycloadditions11,
the
x0xx00000x
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 1

Green Chemistry
Page 2 of 6
View Article Online
COMMUNICATION
Journal Name
DOI: 10.1039/C6GC02776H
multicomponent reactions of nitrogenous molecules12, and so on13. 60 oC or 100 oC, respectively (entries 11 and 12). Finally, we tried to
However, most of the methods are limited to construct 5ꢀsubstituted halve the amount of calcium carbide and H2O, while it led to a lower
pyrazoles while 3ꢀsubstituted or 3,4ꢀdisubstituted pyrazoles act as yield of 52% (entry 13).
vital building blocks of many pharmaceuticals and natural products.
With the optimized reaction conditions in hand (Table 1, entry 10),
In order to expand the richness of synthetic methods, we herein we turned our attention to the scope and limitations of this [3+2]
report an efficient and highly regioselective strategy for the synthesis annulation between Nꢀtosylhydrazones derived from aldehydes and
of 3ꢀsubstituted or 3,4ꢀdisubstituted pyrazoles via transitionꢀmetalꢀ calcium carbide (Table 2). To our delight, a wide range of Nꢀ
free [3+2] cycloaddition/[1,5]ꢀsigmatropic rearrangements (Scheme tosylhydrazones with different substitution patterns could be used as
2). In this process, calcium carbide was used as the acetylide source the substrates, generating the corresponding products in moderate to
to perform with Nꢀtosylhydrazones14,15 derived from aldehydes or good yields under the standard reaction conditions. For R’ = H, Me,
ketones.
Cl, CN, OMe, tꢀBu or NMe2, the starting materials smoothly
transferred to the corresponding products in 59ꢀ83% yields (3aꢀ3g).
The substrate with a substituent on the meta- or orthoꢀposition of the
phenyl ring could also transform to the desired products in good
yields (3hꢀ3j). In general, Nꢀtosylhydrazones with electronꢀneutral
or electronꢀdonating substituents furnished the desired products (3aꢀ
3b, 3eꢀ3g, 3j) in higher yields than those with electronꢀwithdrawing
groups (3cꢀ3d, 3hꢀ3i). Furthermore, 5ꢀbromoꢀ2ꢀmethoxyphenylꢀ, 1ꢀ
naphthylꢀ, 2ꢀfuranylꢀ and 3ꢀpyridylꢀbearing Nꢀtosylhydrazones were
also found to be good substrates, delivering the products (3kꢀ3l, 3nꢀ
3o) in 51ꢀ73% yields. Remarkably, Nꢀtosylhydrazone derived from
aliphatic aldehyde was compatible with the reaction conditions to
afford the corresponding product 3m, albeit with lower efficiency.
Scheme 2. R1 migration in this transformation
.
Results and discussion
Table 1. Optimization of the reaction conditions.a
Table 2. Substrate scope of N-tosylhydrazones derived from aldehydes.a
Entry
Base
Solvent
T (oC)
Yield of 3ab (%)
1
2
3
4
5
6
7
8
9
10
11
12
13c
Cs2CO3
KOH
K2CO3
tꢀBuOLi
Et3N
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
THF
THF
THF
THF
THF
80
80
80
80
80
80
80
80
80
80
60
100
80
58
32
22
18
trace
29
Dioxane
DMF
18
CH3CN
Toluene
DMSO
DMSO
DMSO
DMSO
trace
n.d.
86 (79)
66
80
52
a
Reaction conditions: All reactions were performed with 1a (0.5 mmol), 2a (2 mmol),
base (0.5 mmol), H2O (2.5 mmol) and 2.0 mL solvent at 80 oC for 6 h unless otherwise
noted. b Yields were analyzed by GCꢀMS using nꢀdodecane as an internal standard. The
number in the parentheses is isolated yield. c 2a (1 mmol), H2O (1.25 mmol).
At the outset of this transformation, we treated Nꢀtosylhydrazone
(1a) with calcium carbide (2) as the model substrates for reaction
development (Table 1). Initially, the desired product 3a was obtained
in 58% yield under simple conditions that Cs2CO3 was used as base
and 5 equiv H2O (see Supporting Information for details) were added
a Reaction conditions: All reactions were performed with 1 (0.5 mmol), 2 (2 mmol), base
(0.5 mmol), H2O (2.5 mmol) and 2.0 mL solvent at 80 oC for 6 h unless otherwise noted.
o
to THF in a Schlenk tube at 80 C for 6 h (entry 1). Screening of
various bases, such as KOH, K2CO3, tꢀBuOLi and Et3N, did not
improve the yield of 3a (entries 2ꢀ5). A series of solvents were then
tested and DMSO was found to be the best choice for this
transformation, elevating the yield to 86% (entry 6ꢀ10). Besides, the
yield dropped to 66% or 80% when the temperature was changed to
To further define the scope of our method, the substrate scope was
extended to different types of Nꢀtosylhydrazones derived from
ketones, as shown in Table 3. Initially, we conducted the reaction
between Nꢀtosylhydrazones derived from acetophenone (4a) and
calcium carbide (2) under the standard conditions (Scheme 1). The
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

Page 3 of 6
Journal Name
Green Chemistry
View Article Online
COMMUNICATION
DOI: 10.1039/C6GC02776H
reaction afforded the pyrazole 5a and 5a’ with high regioselectivity,
Considering that the Nꢀtosylhydrazones are easily obtained by
and 5a was isolated in 77% yield. These two regioisomers could be condensation reactions between tosylhydrazides and aldehydes or
explained through process that involves [3+2] dipolar ketones, we then developed a oneꢀpot synthesis of 3,4ꢀsubstituted
cycloaddition, subsequent [1,5] sigmatropic rearrangements and pyrazoles through the use of Nꢀtosylhydrazones generated in situ
aromatization. The aryl group has a higher electron density than the (Scheme 3). Therefore, mixture of acetophenone and
a
a
6
alkyl group, so that it showed higher migration ability in the [1,5] tosylhydrazide was stirred at 70 oC for 2 h in methanol, followed by
rearrangement, making 5a as the major isomer.11a,11b The removal of the solvent. The remaining crude mixture was then
observation of two regioisomers prompted us to investigate the treated with CaC2, Cs2CO3, H2O, and DMSO under the standard
influence of the substituents R1 and R2 in the outcome of the reaction conditions. Gratifyingly, the desired product 5a could also
reactions. Notably, the reaction system tolerates a variety of valuable be obtained in similar yield and regioselectivity compared to those
functional groups on the aryl ring of the Nꢀtosylhydrazones, described in Table 3. This reaction demonstrates the potential of this
including Me, I, COOMe, CF3, SMe, F, Cl and Br substituents (5bꢀ method for the convenient synthesis of various pyrazoles directly
5j). In these cases, target products were obtained in good yields with from widely available aldehydes or ketones.
regioselectivities of more than 5: 1, providing ample potential for
further synthetic elaborations. Both disubstituted and 2ꢀnaphthylꢀ
substituted Nꢀtosylhydrazones smoothly underwent the annulation to
afford the desired products 5k, and 5l in 90% and 76% yields
respectively, with excellent regioselectivities. Pleasingly, when Nꢀ
tosylhydrazone derived from aliphatic ketones was examined, 5m
was obtained in 46% yield as the major isomer. The scope of R2
groups was then investigated. For R2 = Ph, Et or nꢀPr, the Scheme 3. One-pot synthesis of 5a and 5a’ from acetophenone
.
Reaction
(0.5 mmol), tosylhydrazide (0.5 mmol), reflux, 2 h; 2) CaC2 (2
mmol), Cs2CO3 (0.5 mmol), H2O (2.5 mmol), DMSO (2 mL), 80 oC, 6 h.
conditions: 1)
6
corresponding products could be afforded in 69ꢀ75% yields (5nꢀ5p).
Inspired by the results above in Table 2, we tried to use Nꢀ
tosylhydrazones derived from heterocyclic ketones as substrates but
failed.
In order to demonstrate the potential practical applications of this
protocol, we conducted the reaction on a gram scale (see Supporting
Information for details), using 2.74 g (10 mmol) Nꢀtosylhydrazone
1a to produce 0.92 g of 1Hꢀpyrazole 3a with a yield of 64%.
Table 3. Substrate scope of N-tosylhydrazones derived from ketones.a, b
To gain more insights into these two transformations, several
control experiments were conducted. First, diazo compound 7 was
used to take the place of Nꢀtosylhydrazone in the [3+2]
cycloaddition under the standard conditions.16 The corresponding
pyrazole product 5a was generated in 61% yield, which means the
diazo compound may be an intermediate in this transformation
(Scheme 4, eq 1). Deuteriumꢀlabeling experiments were next carried
out. The reaction of 1a and 2 was performed in dry DMSO at 80 oC
for 6 h in the presence of Cs2CO3 and D2O. It was found that the
reaction afforded a mixture of 3a and [D2]ꢀ3a (1: 6.8 ratio) in 75%
a Reaction conditions: All reactions were performed with 4 (0.5 mmol), 2 (2 mmol), base
(0.5 mmol), H2O (2.5 mmol) and 2.0 mL solvent at 80 oC for 6 h unless otherwise noted.
b Only the major isomer 5 was shown in Table 3, yield of 5 was isolated yield, the ratio
of 5 and 5’ was detected by GC/MS using nꢀdodecane as an internal standard.
Scheme 4. Control experiments.
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 3

Green Chemistry
Page 4 of 6
View Article Online
COMMUNICATION
Journal Name
DOI: 10.1039/C6GC02776H
total yield (Scheme 4, eq 2). Moreover, the treatment of 4a under the
In summary, we have successfully developed a facile
same conditions gave a mixture of 5a and [D2]ꢀ5a (1: 7.3 ratio) in transitionꢀmetalꢀfree method for the preparation of substituted
80% total yield (Scheme 4, eq 3). The structures of [D2]ꢀ3a and [D2]ꢀ pyrazoles via [3+2] cycloaddition of ꢀtosylhydrazones derived
N
5a showed that the hydrogen or deuterium atom on N1 was shifted from aldehydes or ketones with calcium carbide. Deuteriumꢀ
from C3 or C4 of the pyrazole ring, respectively. In addition, [1,3] labeling experiments have been conducted to clarify the
sigmatropic shift is orbitalꢀsymmetry forbidden that should be reaction pathways that [1,5] sigmatropic rearrangements are
solventꢀparticipating process during aromatization, while [D1]ꢀ or involved in the transformation. Moreover, the oneꢀpot synthesis
[D3]ꢀ3a were not observed. Therefore, we deduced that the of pyrazoles from readily available aldehydes or ketone is also
transformation ended up with multiple [1,5]ꢀH shifts but not a [1,3]ꢀ successfully developed. In addition, the available starting
H shift during the process of aromatic isomerization.17
material (CaC2), the superbasic catalytic conditions
Taking into account of the experimental results, we proposed the (Cs2CO3/DMSO), and the valuable reaction products make this
mechanism for the synthesis of substituted pyrazoles 3 and 5 protocol attractive for both academia and industry. Further
outlined in Scheme 5. Initially, the deprotonation of Nꢀ applications of this reaction are currently underway in our
tosylhydrazone 4 in the presence of Cs2CO3 gives the cesium salt A. laboratory.
In one possible way, the reactive diazo compound B is rapidly
generated in situ, followed by a [3+2] cycloaddition with [D2]ꢀ
acetylene gas to afford 3Hꢀpyrazole compound E (Path I). Another
Acknowledgements
possibility is that nucleophilic addition of the counter Nꢀanion of This work was supported by the National Key Research and
intermediate A to [D2]ꢀacetylene gas affords the carbonic anion Development Program of China (2016YFA0602900), the
intermediate C. Subsequent intramolecular nucleophilic attack of the National Natural Science Foundation of China (21490572 and
carbonic anion species of C leads to the generation of intermediate D. 21420102003), Pearl River S&T Nova Program of Guangzhou
Then, the Ts anion and cesium ion eliminate from intermediate D to (201610010160) for financial support.
deliver the 3Hꢀpyrazole compound E (Path II). The result of Eq. 1 in
Scheme 4 appears to be strong evidence for possible involvement of
the diazo intermediate, although Path II cannot be ruled out. The
Notes and references
nonaromatic 3Hꢀpyrazole has a trend to isomerize to an aromatic
1Hꢀpyrazole. Therefore, when R1 is H, [D2]ꢀ3 is formed via a [1,5ꢀH]
shift and a tautomerism. When R1 is an electronꢀrich group that has
higher migration ability, relative to the alkyl group, a migration of
R1 to C4 through the transition state F must be favored. The
subsequent multiple [1,5]ꢀsigmatropic rearrangements lead to the
formation of [D2]ꢀ5.
1
a) M.ꢀO. Simon and C.ꢀJ. Li, Chem. Soc. Rev., 2012, 41, 1415; b) A.
Chanda and V. V. Fokin, Chem. Rev., 2009, 109, 725; c) M. Sutter, E.
D. Silva, N. Duguet, Y. Raoul, E. Métay and M. Lemaire, Chem. Rev.,
2015, 115, 8609; d) W. Wu and H. Jiang, Acc. Chem. Res., 2014, 47
,
2483; e) I.ꢀT. Trotuꢁ, T. Zimmermann and F. Schüth, Chem. Rev.,
2014, 114, 1761.
2
3
D. Yu, Y. N. Sum, A. C. C. Ean, M. P. Chin, and Y. Zhang, Angew.
Chem. Int. Ed., 2013, 52, 5125.
a) R. Matake, Y. Adachi and H. Matsubara, Green Chem., 2016, 18
,
2614; b) K. S. Rodygina and V. P. Ananikov, Green Chem., 2016, 18
,
482.
4
5
N. Kaewchangwat, R. Sukato, V. Vchirawongkwin, T. Vilaivan, M.
Sukwattanasinittc and S. Wacharasindhu, Green Chem., 2015, 17
,
460.
a) W. Zhang, H. Wu, Z. Liu, P. Zhong, L. Zhang, X. Huang and J.
Cheng, Chem. Commun., 2006, 42, 4826; b) P. Chuentragool, K.
Vongnam, P. Rashatasakhon, M. Sukwattanasinitt and S.
Wacharasindhu, Tetrahedron, 2011, 67, 8177.
6
7
a) Y. N. Sum, D. Yu and Y. Zhang, Green Chem., 2013, 15, 2718; b)
A. Hosseini, D. Seidel, A. Miska, and P. R. Schreiner, Org. Lett.
,
2015, 17, 2808.
a) R. Matake, Y. Niwa and H. Matsubara, Org. Lett., 2015, 17, 2354;
b) S. P. Teong, D. Yu, Y. N. Sum and Y. Zhang, Green Chem., 2016,
18, 3499.
8
9
S. Fustero, M. SánchezꢀRoselló, P. Barrio and A. SimónꢀFuentes,
Chem. Rev., 2011, 111, 6984.
a) T. D. Penning, J. J. Talley, S. R. Bertenshaw, J. S. Carter, P. W.
Collins, S. Docter, M. J. Graneto, L. F. Lee, J. W. Malecha, J. M.
Scheme 5. Proposed mechanism.
Miyashiro, R. S. Rogers, D. J. Rogier, S. S. Yu, G. D. Anderson, E. G.
Burton, J. N. Cogburn, S. A. Gregory, C. M. Koboldt, W. E. Perkins,
K. Seibert, A. W. Veenhuizen, Y. Y. Zhang and P. C. Isakson, J. Med.
Conclusions
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

Page 5 of 6
Journal Name
Green Chemistry
View Article Online
COMMUNICATION
DOI: 10.1039/C6GC02776H
Chem.; 1997, 40, 1347; b) D. J. Dale, P. J. Dunn, C. Golightly, M. L. 16 For the synthesis of diazo compounds, see: F. Friscourt, C. J. Fahrni
Hughes, P. C. Levett, A. K. Pearce, P. M. Searle, G. Ward and A. S. and G.ꢀJ. Boons, Chem. Eur. J., 2015, 21, 13996.
Wood, Org. Process Res. Dev., 2000, , 17; c) A. GuzmanꢀPerez, R. 17 a) S. Hou, X. Li and J. Xu, J. Org. Chem., 2012, 77, 10856; b) S. Hou,
4
T. Wester, M. C. Allen, J. A. Brown, A. R. Buchholz, E. R. Cook, W.
W. Day, E. S. Hamanaka, S. P. Kennedy, D. R. Knight, P. J.
Kowalczyk, R. B. Marala, C. J. Mularski, W. A. Novomisle, R. B.
Ruggeri, W. R. Tracey and R. J. Hill, Bioorg. Med. Chem. Lett., 1996,
X. Li and J. Xu, Org. Biomol. Chem., 2014, 12, 4952; c) M. C. Pérezꢀ
Aguilar and C. Valdés, Angew. Chem. Int. Ed., 2015, 54, 13729.
6
, 1819; d) M. Kim, C. Sim, D. Shin, E. Suh and K. Cho, Crop Prot.
2006, 25, 542; e) D. Marcic, Exp. Appl. Acarol., 2005, 36, 177.
10 (a) S. T. Heller and S. R. Natarajan, Org. Lett., 2006, , 2675; (b) J.
,
8
Ichikawa, M. Kobayashi, Y. Noda, N. Yokota, K. Amano and T.
Minami, J. Org. Chem., 1996, 61, 2763; (c) B. S. Gerstenberger, M.
R. Rauckhorst and J. T. Starr, Org. Lett., 2009, 11, 2097; (d) Z. X.
Wang and H. L. Qin, Green Chem., 2004, 6, 90.
11 a) N. Jianga and C.ꢀJ. Li, Chem. Commun., 2004, 40, 394; b) M. C.
PérezꢀAguilar and C. Valdés, Angew. Chem. Int. Ed., 2013, 52, 7219;
c) M. Suri, T. Jousseaume, J. J. Neumann and F. Glorius, Green
Chem., 2012, 14, 2193; d) J. J. Neumann, M. Suri and F. Glorius,
Angew. Chem. Int. Ed., 2010, 49, 7790; e) X. Deng and N. S. Mani,
Org. Lett., 2008, 10, 1307; f) R. R. Merchant, D. M. Allwood, D. C.
Blakemore and S. V. Ley, J. Org. Chem., 2014, 79, 8800; g) Y. Ding,
T. Zhang, Q.ꢀY. Chen and C. Zhu, Org. Lett., 2016, 18, 4206.
12 a) S. Majumder, K. R. Gipson, R. J. Staples and A. L. Odom, Adv.
Synth. Catal., 2009, 351, 2013; b) G. Zhang, H. Ni, W. Chen, J. Shao,
H. Liu, B. Chen and Y. Yu, Org. Lett., 2013, 15, 5967; c) X. Tang, L.
Huang, J. Yang, Y. Xu, W. Wu and H. Jiang, Chem. Commun., 2014,
50, 14793; d) B. R. Kim, G. H. Sung, K. E. Ryu, S.ꢀG. Lee, H. J.
Yoon, D.ꢀS. Shinc and Y.ꢀJ. Yoon, Chem. Commun., 2015, 51, 9201.
13 a) C. Guo, B. Sahoo, C. G. Daniliuc and F. Glorius, J. Am. Chem.
Soc., 2014, 136, 17402; b) G. Shan, P. Liu and Y. Rao, Org. Lett.,
2011, 13, 1746; c) J. Hu, Y. Cheng, Y. Yang and Y. Rao, Chem.
Commun., 2011, 47, 10133; d) X.ꢀW. Fan, T. Lei, C. Zhou, Q.ꢀY.
Meng, B. Chen, C.ꢀH. Tung and L.ꢀZ. Wu, J. Org. Chem., 2016, 81
,
,
7127; e) V. Marković and M. D. Joksović, Green Chem., 2015, 17
842; f) Q. Zhang, M. Yu, J. Yuan, R. Zhang, Y. Liang, J. Tian and D.
Dong, J. Org. Chem., 2016, 81, 6036; g) L. Wang, X. Yu, X. Feng
and M. Bao, J. Org. Chem., 2013, 78, 1693; h) X. Li, L. He, H. Chen,
W. Wu and H. Jiang, J. Org. Chem., 2013, 78, 3636.
14 For reviews, see: a) J. Barluenga and C. Valdés, Angew. Chem. Int.
Ed., 2011, 50, 7486; b) Z. Shao and H. Zhang, Chem. Soc. Rev., 2012,
41, 560; c) Q. Xiao, Y. Zhang and J. Wang, Acc. Chem. Res., 2013,
46, 236; d) Y. Xia, Y. Zhang and J. Wang, ACS Catal., 2013, 3, 2586.
15 a) J. Barluenga, M. TomásꢀGamasa, F. Aznar and C. Valdés, Angew.
Chem. Int. Ed., 2010, 49, 4993; b) J. Barluenga, M. TomásꢀGamasa
and C. Valdés, Angew. Chem. Int. Ed., 2012, 51, 5950; c) H. Li, L.
Wang, Y. Zhang and J. Wang, Angew. Chem. Int. Ed., 2012, 51, 2943;
d) Z. Liu, H. Tan, L. Wang, T. Fu, Y. Xia, Y. Zhang and J. Wang,
Angew. Chem. Int. Ed., 2015, 54, 3056; e) A.ꢀJ. Xia, T.ꢀR. Kang, L.
He, L.ꢀM. Chen, W.ꢀT. Li, J.ꢀL. Yang and Q.ꢀZ. Liu, Angew. Chem.
Int. Ed., 2016, 55, 1441; f) D. P. Ojha and K. R. Prabhu, Org. Lett.,
2015, 17, 18; g) Q. Ding, B. Cao, J. Yuan, X. Liua and Y. Peng, Org.
Biomol. Chem., 2011, 9, 7; h) A. K. Yadav, V. P. Srivastava and L. D.
S. Yadav, Chem. Commun., 2013, 49, 2154; i) W. Xiong, C. Qi, H.
He, L. Ouyang, M. Zhang and H. Jiang, Angew. Chem. Int. Ed., 2015,
54, 3084; j) C. Zhu, J. Li, P. Chen, W. Wu, Y. Ren and H. Jiang, Org.
Lett., 2016, 18, 1470.
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 5

Green Chemistry
Page 6 of 6
View Article Online
DOI: 10.1039/C6GC02776H
Calcium carbide was used as the acetylide source to synthesize substituted pyrazoles
via [3+2] cycloaddition/[1,5] sigmatropic rearrangements.