[Cu]-catalyzed direct coupling of dibromoalkenes: Synthesis of symmetrical 1,3-diynes and triazoles

Article abstract of DOI:10.1080/00397911.2017.1315732

An efficient [Cu]-catalyzed homocoupling of 1,1-dibromoalk-1-enes is described for the synthesis of symmetrical 1,3-diyines. The method showed good substrate scope and amenable to aryl and heteroaryl systems. Significantly, the strategy was also successfully applied to the sequential one-pot synthesis of triazoles.

Full text of DOI:10.1080/00397911.2017.1315732

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: http://www.tandfonline.com/loi/lsyc20
[Cu]-Catalyzed Direct Coupling of Dibromoalkenes:
Synthesis of Symmetrical 1,3-Diynes and Triazoles
Lodi Mahendar, Bokka Venkat Ramulu & Gedu Satyanarayana
To cite this article: Lodi Mahendar, Bokka Venkat Ramulu & Gedu Satyanarayana (2017): [Cu]-
Catalyzed Direct Coupling of Dibromoalkenes: Synthesis of Symmetrical 1,3-Diynes and Triazoles,
Synthetic Communications, DOI: 10.1080/00397911.2017.1315732
To link to this article: http://dx.doi.org/10.1080/00397911.2017.1315732
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Date: 12 April 2017, At: 22:06

[Cu]-Catalyzed Direct Coupling of Dibromoalkenes: Synthesis of Symmetrical 1,3-
Diynes and Triazoles
Lodi Mahendar1, Bokka Venkat Ramulu1, Gedu Satyanarayana1
1Department of Chemistry, Indian Institute of Technology, Hyderabad
Corresponding Author: Gedu Satyanarayana, Department of Chemistry, Indian Institute
of Technology Hyderabad, Kandi – 502 285, Sangareddy, Telangana, INDIA. E-mail:
gvsatya@iith.ac.in
Abstract
An efficient [Cu]-catalyzed homo-coupling of 1,1-dibromoalk-1-enes, is described, for
the synthesis of symmetrical 1,3-diyines. The method showed good substrate scope and
amenable to aryl and heteroaryl systems. Significantly, the strategy was also successfully
applied to the sequential one-pot synthesis of triazoles.
Graphical Abstract
Symmetrical 1,3-diynes are ubiquitous structural motifs for the accomplishment of
natural products, pharmaceuticals, supramolecular structures, π-conjugated polymers and
materials.1 The well-established classical method for the construction of symmetric 1,3-
diynes is oxidative homo-coupling reactions of terminal alkynes, reported by Carl Glaser
in 1869, in the presence of Cu(I) salt and oxygen air.2 Subsequently, Eglinton3 and Hay.4
disclosed modified versions to improve versatility of the method. On the other hand,
1

interestingly, Chodkiewicz-Cadiot et al., reported the synthesis of unsymmetrical 1,3-
diynes from halo-alkynes using [Cu]-catalysis.5 While, Yu and co-workers demonstrated
the copper-catalyzed decaroxylative coupling of propiolic acid with terminal acetylenes
to accomplish unsymmetrical 1,3-diyines.6 Another interesting protocol was disclosed by
Rossi et al., for the synthesis of symmetrical 1,3-diynes under [Pd]-catalysis.7 Notably,
the research group of Lei disclosed [Ni]-mediated cross-coupling between two different
terminal acetylenes, in which one acetylene was used in excess over the other, for the
accomplishment of unsymmetrical acetylenes.8 Nevertheless, the above mentioned
approaches have some drawbacks, such as, prefunctionalization of precursor acetylenes.
Since homo-coupling certainly requires preparation of terminal acetylenes using the
following reactions: a) Corey-Fuchs reaction with aldehydes;9 b) Seyferyth-Gilbert
homologation with aldehydes;10 c) Fritsch-Buttenberg-Wiechell rearrangement of vinyl
bromides;11 d) Sonogashira coupling of haloarenes with metal (Si or Sn)-acetylides
followed by reductive hydrogenation.12 Therefore, it is essential to develop new and
efficient methods for the accomplishment of conjugate 1,3-diynes, which minimizes
synthetic steps and minimizes the waste generation.
Significantly, 1,1-dibromoalk-1-enes are identified as stable and easily accessible from
simple bench-top aldehydes, and useful in synthetic organic transformations.13,14
Subsequently, catalytic processes for the synthesis of symmetrical 1,3-diynes starting
from 1,1-dibromoalk-1-enes via in-situ generation of 1-bromoalkyne is feasible synthetic
transformation. In this context, few metal-catalytic strategies have already been
established for the synthesis of symmetrical 1,3-diynes, using 1,1-dibromoalk-1-enes as
2

substrates.15–20 In continuation of our research interests on transition-metal-catalyzed
transformations,21 herein we describe an efficient strategy for the synthesis of
symmetrical 1,3-diynes through the direct homo-coupling of 1,1-dibromoalk-1-enes
mediated by the [Cu]-catalyst (i.e. direct treatment of Corey-Fuchs products without
subsequent preparation of terminal acetylenes). Significantly, unlike earlier reports, the
present strategy was further applied to the sequential one-pot synthesis of triazoles, via
in-situ treatment of Glaser 1,3-diynes.
To begin with, initially, we examined the reaction of 1,1-dibromoalkene 1a in the
presence of CuI/1,10-Phenth in CH2Cl2, base Cs2CO3 at 40 C. However, the desired
symmetrical 1,3-diyne product 2a was not formed (Table 1, entry 1). Interestingly, the
reaction in DMF and 1,4-dioxane, gave the product 2a in moderate yields along with the
recovery of starting material 1a (Table 1, entries 2 to 3). Gratifyingly, the solvent CH3CN
was found to be the best and gave the product 2a, in excellent yield (Table 1, entry 4).
The reaction was inferior with catalytic amount of CuBr (Table 1, entry 5). On the other
hand, the reaction in DMSO, furnished 2a, in moderate yields (Table 1, entry 6).
However, the reaction under other variants, such as, with different bases in CH3CN was
not effective (Table 1, entries 7 to 10).
With these optimized conditions in hand (Table 1, entry 4), to check the scope and
generality of the method, the reaction was explored with other 1,1-dibromoalk-1-enes
1a 1n. To our delight, as expected, the reaction was amenable and smoothly furnished
the symmetrical 1,3-diynes 2a 2n, in very good to excellent yields (Table 2). Notably,
3

the reaction showed good substrate scope, as the method was compatible to the substrates
raging from simple to electron rich aromatic moieties (Table 2). Significantly, the
reaction was also amenable with heteroaryl moieties, such as furan and thiophene rings
(Table 2, entries 2m & 2n). However, it was noticed that the reaction of vinyl dibromide
1o22 derived from phenyl acetaldehyde, was unsuccessful to deliver the 1,3-diyne 2o,
under the established conditions (i.e. neither the starting material nor the product was
isolated). Also, the reaction was unsuccessful at relatively low temperature (80 C), and
in the presence of mild bases, such as, Na2CO3 and K2CO3. This may be due to relatively
more reactive nature of benzylic hydrogen atoms, which are in conjugation to both
aromatic and vinyl of the dibromide 1o.
Recently, the research group of Manish Bhattacharjee disclosed the synthesis of triazoles
by treating 1,3-diynes with NaN3, in hot DMSO.23 Therefore, in this context, unlike
previous reports, we believed that the sequential one-pot synthesis of triazoles would be
feasible by in-situ treatment of symmetrical 1,3-diynes 2 with NaN3. Thus, after
confirming the formation of symmetrical 1,3-diynes 2 from TLC, NaN3 (2 equiv) and
DMSO (1 mL) were added to the reaction mixture and continued at hot conditions (80
C) for an additional time (10 h). To our delight, the reaction was quite successful and
furnished the triazoles 2a 2n, in good to very good yields, in a sequential one-pot
operation (Table 3). Significantly, this sequential one-pot strategy enabled the
construction of three (two C-N and one C-C) bonds quite efficiently.
4

In summary, we have developed an efficient [Cu]-catalysis for the synthesis of
symmetrical 1,3-diyines through direct treatment of 1,1-dibromoalk-1-enes. The
method showed good substrate scope and amenable to aryl as well as heteroaryl
systems. Significantly, unlike previous reports, the strategy was also applied to the
sequential one-pot synthesis of triazoles.
IR spectra were recorded on a FTIR spectrophotometer. 1H NMR spectra were
recorded on 400 MHz spectrometer at 295 K in CDCl3; chemical shifts (δ ppm) and
coupling constants (Hz) are reported in standard fashion with reference to either internal
standard tetramethylsilane (TMS) (δH=0.00 ppm) or CHCl3 (δH=7.25 ppm). 13C NMR
spectra were recorded on 100 MHz spectrometer at RT in CDCl3; chemical shifts (δ ppm)
are reported relative to CHCl3 [δC=77.00 ppm (central line of triplet)]. In the 13C NMR,
the nature of carbons (C, CH, CH2, and CH3) was determined by recording the DEPT-135
spectra and is given in parentheses and noted as s = singlet (for C), d = doublet (for CH),
t = triplet (for CH2) and q = quartet (for CH3). In the 1H NMR, the following
abbreviations were used throughout: s = singlet, d = doublet, t = triplet, q = quartet, qui
=quintet, m = multiplet and br s. = broad singlet. The assignment of signals was
confirmed by 1H, 13C CPD (carbon proton decoupled), and DEPT spectra. High-
resolution mass spectra (HR-MS) were recorded using Q-TOF multimode source.
Melting points were determined on an electrothermal melting point apparatus and are
uncorrected. Benzaldehydes, immidazole, aryl halides, methyl iodide, bromoethane, Mg
metal and Na2SO4 were commercially available (local made) used without further
purification, CuI, 1,10-phenonthroline, Cs2CO3, K3PO4, K2CO3, Na2CO3, and NaHCO3
5

purchased from commercial source. All dry solvents were used, toluene, Dioxane and
THF were dried over sodium metal, DCM, CH3CN, DMSO and DMF were dried over
calcium hydride.
All small scale dry reactions were carried out using standard syringe-septum technique.
Reactions were monitored by TLC on silica gel using a combination of petroleum ether
and ethyl acetate as eluents. Solvents were distilled prior to use; petroleum ether with a
boiling range of 40 to 60 C was used. Acme’s silica gel (60–120 mesh) was used for
column chromatography (approximately 20 g per one gram of crude material).
General Procedure For Dibromoalkenes (1,1-Dibromoethenes)
To an ice cold stirred solution of aryl aldehyde (200 mg, 3.7 mmol) and CBr4 (2.0 mmol)
in dry CH2Cl2 (10 mL) was added PPh3 (4.0 mmol) in CH2Cl2 (10 mL) with a dropping
funnel for 10 min. After the reaction was complete, the reaction mixture was
concentrated under reduced pressure and then CHCl3 (20 mL) was added to the residue.
The suspended mixture was filtered to remove triphenylphosphine oxide that was washed
with CHCl3 (2 20 mL). The combined filtrates were concentrated under reduced
pressure and the crude product was purified with column chromatography to give the
pure product dibromoalkene 1.
1-(2,2-Dibromovinyl)-4-Ethylbenzene (1c)
The crude dibromoalkene 1c was purified by column chromatography on silica
using petroleum ether/ethyl acetate (95:05) as eluent and isolated as pale yellow colored
6

oil 81% yield (393 mg): [TLC (petroleum ether/ethyl acetate 9.5:0.5, Rf(4c)=0.40,
Rf(1c)=0.60, UV detection]. 1H NMR (CDCl3 400 MHz): δ=7.45 (d, J=8.3 Hz, 2H), 7.19
(d, J=8.3 Hz, 2H), 2.63 (q, J=7.3 Hz, 2H), 1.23 (t, J=7.3 Hz, 3H) ppm. 13C NMR (CDCl3,
100 MHz): δ=144.9 (Cq), 136.8 (CH), 132.7 (Cq), 128.4 (CH), 127.9 (CH), 88.5 (Cq),
28.7 (CH2), 15.3 (CH3) ppm. IR (MIR-ATR, 4000–600 cm-1): max=2923, 1492, 1343,
1276, 1161, 1051, 961, 745, 680 cm-1. HR-MS (ESI+) m/z calculated for
[C10H11Br2]+=[M+H]+: 288.9222; found: 288.9220.
1-(2,2-Dibromovinyl)-2,3-Dimethoxybenzene (1h)
The crude dibromoalkene 1h was purified by column chromatography on silica using
petroleum ether/ethyl acetate (90:10) as eluent and isolated as yellow colored solid 88%
yield (340 mg): mp 80–82 C; [TLC (petroleum ether/ethyl acetate 9.5:0.5, Rf(4h)=0.40,
Rf(1h)=0.60, UV detection]. 1H NMR (CDCl3 400 MHz): δ=7.62 (s, 1H), 7.29 (d, J=8.8
Hz, 1H), 7.05 (dd, J=8.3 and 7.8 Hz, 1H), 6.91 (d, J=8.3 Hz, 1H), 3.86 (s, 3H), 3.81 (s,
3H) ppm. 13C NMR (CDCl3, 100 MHz): δ=152.6 (Cq), 146.7 (Cq), 132.8 (CH), 129.8
(Cq), 123.7 (CH), 120.8 (CH), 112.7 (CH), 90.5 (Cq), 61. 1 (CH3), 55.8 (CH3) ppm. IR
(MIR-ATR, 4000–600 cm-1): max=2920, 1482, 1340, 1286, 1163, 1054, 961, 745, 683
cm-1. HR-MS (ESI+) m/z calculated for [C10H11Br2O2]+=[M+H]+: 320.9120; found:
320.9122.
General Procedure For 1,3-Dialkynes Synthesis
In an oven -dried Schlenk tube under nitrogen atmosphere were added dibromoalkene 1
(0.50 mmol), CuI (10 mol%), 1,10-Phenthroline (20 mol%) and Cs2CO3 (1.0 mmol)
7

followed by addition of CH3CN (0.5 mL). The resulting reaction mixture was stirred at
110 C for 20–24 h. Progress of the reaction was monitored by TLC until the reaction is
completed. The reaction mixture was quenched by the addition of aq. NH4Cl solution and
extracted with CH2Cl2 (3 10 mL). The organic layers were dried (Na2SO4) and
concentrated in vacuo. Purification of the residue on a silica gel column chromatography
using petroleum ether/ethyl acetate as eluent furnished the 1,3 dialkynes 2.
1,4-Bis(4-Ethylphenyl)Buta-1,3-Diyne (2c)
The crude 1,3-diyne 2c was purified by column chromatography on silica using
petroleum ether/ethyl acetate (95:05) as eluent and isolated as white colored solid 89%
yield (115 mg): mp 76–78 C; [TLC (petroleum ether/ethyl acetate 9.5:0.5, Rf(1c)=0.40,
Rf(2c)=0.30, UV detection]. 1H NMR (CDCl3 400 MHz): δ=7.46 (d, J=7.8 Hz, 2H), 7.20
(d, J=7.8 Hz, 2H), 2.65 (q, J=7.8 Hz, 2H), 1.24 (t, J=7.8 Hz, 3H) ppm. 13C NMR (CDCl3,
100 MHz): δ=144.9 (Cq), 136.8 (CH), 132.6 (Cq), 128.4 (CH), 127.9 (2C, CH), 127.8
(Cq), 88.5 (Cq), 28.7 (CH2), 15.3 (CH3) ppm. IR (MIR-ATR, 4000–600 cm-1): max=2921,
1482, 1353, 1276, 1161, 1051, 960, 745, 686 cm-1. HR-MS (ESI+) m/z calculated for
[C20H19]+=[M+H]+: 259.1481; found: 259.1482.
1,4-Bis(2,3-Dimethoxyphenyl)Buta-1,3-Diyne (2h)
The crude 1,3-diyne 2h was purified by column chromatography on silica using
petroleum ether/ethyl acetate (95:05) as eluent and isolated as white colored solid 81%
yield (130 mg): mp 128–130 C; [TLC (petroleum ether/ethyl acetate 9:1, Rf(1h)=0.40,
Rf(2h)=0.30, UV detection]. 1H NMR (CDCl3 400 MHz): δ=7.08 (dd, J=7.8 and 2.0 Hz,
8

1H), 6.98 (dd, J=8.3 and 7.8 Hz, 1H), 6.92 (dd, J=7.8 and 2.0 Hz, 1H), 3.97 (s, 3H), 3.86
(s, 3H) ppm. 13C NMR (CDCl3, 100 MHz): δ=152.6 (Cq), 151.7 (Cq), 125.9 (CH), 123.9
(CH), 116.5 (Cq), 113.8 (Cq), 78.3 (Cq), 77.8 (Cq), 61. 3 (CH3), 56.0 (CH3) ppm. IR
(MIR-ATR, 4000–600 cm-1): max=2924, 1482, 1330, 1276, 1163, 1054, 961, 745, 688
cm-1. HR-MS (ESI+) m/z calculated for [C20H19O4]+=[M+H]+: 323. 1278; found: 323.
1277.
GENERAL PROCEDURE FOR TRIAZOLE SYNTHESIS
In an oven -dried Schlenk tube under nitrogen atmosphere were added dibromoalkene 1
(0.50 mmol), CuI (10 mol%), 1,10-Phenthroline (20 mol%) and Cs2CO3 (1.0 mmol)
followed by addition of CH3CN (0.5 mL). The resulting reaction mixture was stirred at
110 C for 24 h, after confirming the formation of symmetrical diynes 2 from TLC, NaN3
and DMSO were added to the reaction mixture and continued at hot conditions (80 C)
for additional time (10 h). Progress of the reaction was monitored by TLC until the
reaction is completed. The reaction mixture was quenched by the addition of aq. NH4Cl
solution and extracted with CH2Cl2 (3 10 mL). The organic layers were dried (Na2SO4)
and concentrated in vacuo. Purification of the residue on a silica gel column
chromatography using petroleum ether/ethyl acetate as eluent furnished the triazole 3.
5-(4-Ethylphenyl)-4-((4-Ethylphenyl)Ethynyl)-1H-1,2,3-Triazole (3c)
The crude triazole 3c was purified by column chromatography on silica using petroleum
ether/ethyl acetate (90:10) as eluent and isolated as white colored solid 71% yield (106
mg): mp 88–90 C; [TLC (petroleum ether/ethyl acetate 9:1, Rf(1c)=0.50, Rf(3c)=0.30,
9

UV detection]. 1H NMR (CDCl3 400 MHz): δ=8.06 (d, J=8.3 Hz, 1H), 7.50 (d, J=7.8 Hz,
1H), 7.30 (d, J=8.3 Hz, 1H), 7.21 (d, J=8.3 Hz, 1H), 2.75-2.68 (m, 2H), 1.25 (t, J=7.3 Hz,
3H) ppm. 13C NMR (CDCl3, 100 MHz): δ=145.7 (Cq), 145.4 (Cq), 131.7 (CH), 128.3
(CH), 128.1 (CH), 126.8 (CH), 119.3 (Cq), 28. 9 (CH2), 28. 7 (CH2), 15.4 (CH3), 15.3
(CH3) ppm. IR (MIR-ATR, 4000–600 cm-1): max=2926, 1482, 1350, 1267, 1163, 1054,
961, 740, 683 cm-1. HR-MS (ESI+) m/z calculated for [C20H19N3Na]+=[M+Na]+:
324.1471; found: 324.1470.
5-(Benzo[D][1,3]Dioxol-5-Yl)-4-(Benzo[D][1,3]Dioxol-5-Ylethynyl)-1H-1,2,3-
Triazole (3k)
The crude triazole 3k was purified by column chromatography on silica using petroleum
ether/ethyl acetate (85:15) as eluent and isolated as pale yellow colored solid 73% yield
(121 mg): mp 92–94 C; [TLC (petroleum ether/ethyl acetate 8:2, Rf(1k)=0.50,
Rf(3k)=0.30, UV detection]. 1H NMR (CDCl3 400 MHz): δ=7.21 (d, J=2.0 Hz, 1H), 7.19
(d, J=1.5 Hz, 1H), 7.03 (d, J=1.5 Hz, 2H), 6.86 (s, 1H), 6.84 (s, 1H), 6.06 (s, 4H) ppm.
13C NMR (CDCl3, 100 MHz): δ=151.5 (Cq), 148.0 (Cq), 128.2 (CH), 118.9 (Cq), 111.4
(CH), 109.1 (CH), 104.9 (Cq), 102. 2 (CH2) ppm. IR (MIR-ATR, 4000–600 cm-1):
max=2920, 1504, 1392, 1221, 1155, 1094, 969, 803, 774 cm-1. HR-MS (ESI+) m/z
calculated for [C18H11N3O4Na]+=[M+Na]+: 356.0642; found: 356.0643.
ACKNOWLEDGMENT
We are grateful to the Department of Science and Technology-Science and Engineering
Research Board (DST-SERB) [NO.:SB/S1/OC-39/2014], New Delhi, for the financial
10

support. L.M. and B. V. R. thanks CSIR, New Delhi, for the award of research
fellowship. Thanks to Dr. William P. Unsworth (University of York, UK) for his support.
SUPPORTING INFORMATION
Supporting information for this article is available online at
REFERENCES
1)
(a) Tour, J. M. Chem. Rev. 1996, 96, 537.(b) Nicolaou, K. C.; Petasis, N. A.;
Zipkin, R. E. J. Am. Chem. Soc. 1982, 104, 5560.(c) Zhou, L.; Zhan, H. Y.; Jiang, H. F.
Chin. J. Chem. 2007, 25, 1413. (d) Siemsen, P.; Livingston, R. C.; Diederich, F. Angew.
Chem., Int. Ed. 2000, 39, 2632.(e) Zhang, L. Y.; Wang, L. Chin. J. Chem. 2008, 26,
1601.
2)
(a) Glaser, C. Ber. Dtsch. Chem. Ges. 1869, 2, 422; (b) Glaser, C. Ann. Chem.
Pharm. 1870, 154, 137.
3)
4)
Eglinton, G.; Galbraith, R. J. Chem. Soc. 1959, 889.
(a) Hay, A. S. J. Org. Chem. 1960, 25, 1275. (b) Hay, A. S. J. Org. Chem. 1962,
27, 3320.
5)
(a) Chodkiewicz, W.; Cadiot, P. Compt. Rend. 1955, 241, 1055. (b) Chodkiewicz,
W.; Alhuwalia, J. S.; Cadiot, P.; Willemart, A. Compt. Rend. 1957, 245, 322.
6)
7)
8)
9)
Yu, M.; Pan, D.; Jia, W.; Chen, W.; Jiao, N. Tetrahedron Lett. 2010, 51, 1287.
Rossi, R.; Carpita, A.; Bigelli, C. Tetrahedron Lett. 1985, 6, 523.
Yin, W.; He, C.; Chen, M.; Zhang, H.; Lei, A. Org. Lett. 2009, 11, 709.
Corey, E. J.; Fuchs, P. L. Tetrahedron Lett. 1972, 13, 3769.
11

10)
(a) Seyferth, D.; Hilbert, P.; Marmor, R. S. J. Am. Chem. Soc. 1967, 89, 4811. (b)
Gilbert, J. C.; Weerasooriya, U. J. Org. Chem. 1979, 44, 4997.
11)
12)
Vaitiekunas, F. F.; Nord, F. F. J. Org. Chem. 1954, 19, 902.
(a) Trost, B. M., Fleming, I., Eds.; Pergamon Press: Oxford, UK, 1990, 3, 521. (b)
Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett. 1975, 16, 4467.
13) (a) Chelucci, G. Chem. Rev. 2012, 112, 1344; (b) Bédard, A. –C.; Collins, S. K. J.
Am. Chem. Soc., 2011, 133, 19976; (c) Léséleuc, M.; Godin, E.; Parisien-Collette, S.;
Lévesque, A.; Collins, S. K. J. Org. Chem., 2016, 81, 6750.
14)
15)
Ramirez, F.; Desai, N. B.; Mckelvie, N. J. Am. Chem. Soc. 1962, 84, 1745.
(a) Coste, A.; Couty, F.; Evano, G. Synthesis 2010, 1500; (b) Suzuki, H.; Aihara,
M.; Yamamoto, H.; Takamoto, Y.; Ogawa, T. Synthesis 1988, 236. (c) Huang, Z..; Shang,
R.; Zhang, Z. -R.; Tan, X. -D. Xiao, X.; Fu, Y. J. Org. Chem., 2013, 78, 4551; (d)
Wensheng, Z.; Wenjing, X.; Fei, Z. Huaxue Shiji 2015, 37, 1047.
16)
17)
18)
3517.
19)
20)
21)
Hui, J.; Chunxiang, K. Chin. J. Chem. 2011, 29, 592.
Yan, J.; Wang, L. Synth. Commun. 2005, 35, 2333.
Vanderesse, R.; Fort, Y.; Becker, S.; Caubere, P. Tetrahedron Lett. 1986, 27,
Galamb, V.; Gopal, M.; Alper, H. Organometallics 1983, 2, 801.
Shen, W.; Thomas, S. A. Org. Lett. 2000, 2, 2857.
(a) Mahendar, L.; Krishna, J.; Reddy, A. G. K.; Ramulu, B. V.; Satyanarayana, G.
Org. Lett. 2012, 14, 628; (b) Mahendar, L.; Satyanarayana, G. J. Org. Chem. 2014, 79,
2059; (c) Mahendar, L.; Reddy, A. G. K.; Krishna, J.; Gedu Satyanarayana. J. Org.
Chem. 2014, 79, 8566; (d) Mahendar, L.; Satyanarayana, G. J. Org. Chem. 2015, 80,
12

7089; (e) Krishna, J.; Reddy, A. G. K.; Satyanarayana, G. Synlett 2013, 967; (f) Krishna,
J.; Reddy, A. G. K.; Satyanarayana, G. Tetrahedron Lett. 2014, 55, 861; (g) Ravi Kumar,
D; Satyanarayana, G. Org. Lett. 2015, 17, 5894.
22)
23)
King, S. M.; Ma, X.; Herzon, S. B. J. Am. Chem. Soc. 2014, 136, 6884.
Das, U. K.; Jena, R. J.; Bhattacharjee, M. RSC Adv., 2014, 4, 21964.
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Table 1: Optimization conditions for the synthesis of symmetrical 1,3-diynes 2.a
Entry Catalyst (10
mol%)
Ligand (20
mol%)
Base (2
equiv)
Solvent
Temp
( C)
40
Yieldb 2a (%)
1
2
3
4
5
6
7
8
9
10
CuI
CuI
CuI
CuI
CuBr
CuI
CuI
CuI
CuI
CuI
1,10-Phenth Cs2CO3
1,10-Phenth Cs2CO3
1,10-Phenth Cs2CO3
1,10-Phenth Cs2CO3
1,10-Phenth Cs2CO3
1,10-Phenth Cs2CO3
1,10-Phenth K2CO3
1,10-Phenth K3PO4
1,10-Phenth NaHCO3
1,10-Phenth Na2CO3
DCM
DMF
SM (1a)c
120
50% + SM (1a)c
46% + SM (1a)c
91%
1,4-Dioxane 110
CH3CN
CH3CN
DMSO
CH3CN
CH3CN
CH3CN
CH3CN
110
110
110
110
110
110
110
20% + SM (1a)c
48% + SM (1a)c
50% + SM (1a)c
60% + SM (1a)c
42% + SM (1a)c
53% + SM (1a)c
aAll reactions were carried out on (0.5 mol) scale of 1a in 0.5 mL solvent. bIsolated yields
of chromatographically pure products. cStarting material was also recovered.
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Table 2: Synthesis of Symmetrical 1,3-diynes 2.a
aReaction conditions: 1a 1n (0.5 mmol), Cs2CO3 (2 equiv), CuI (10 mol%), 1,10-Phenth
(20 mol%), 0.5 mL CH3CN, at 110 C for 24 h. Yields are isolated yields of
chromatographically pure products. bThe reaction was not successful.
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Table 3: Synthesis of triazoles 3.a,b
aReaction conditions: 1a-1k (0.5 mmol), Cs2CO3 (2 equiv), CuI (10 mol%), 1,10-Phenth
(20 mol%), CH3CN (0.5 mL), at 110 C for 24 h then added NaN3 (2equiv) and DMSO (1
mL) at 80 C for 12 h. bYields are isolated yields of chromatographically pure products.
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