4
Tetrahedron Letters
4. Tang, J.; Zhao, X. RSC Adv. 2012, 2, 5488-5490.
5. (a) Liu, Y.; Wang, C.; Wang, X.; Wan, J.-P. Tetrahedron Lett.
2013, 54, 3953-3955; (b) Perrone, S.; Bona, F.; Troisi, L.
Tetrahedron 2011, 67, 7386-7391.
Although not clear, the observed beneficial effect with TBAI
or KI could be attributed to the probable halogen exchange23
with 2b in order to promote the initial formation of 2a and
subsequent formation of 2c during the catalytic cycle.
Formation of alkynyl palladium,18,19 dialkynyl Pd(II)
intermediate,25 and reductive homocouplings25 are well
documented in the literature.
6. (a) Meng, X.; Li. C.; Han, B.; Wang, T.; Chen, B. Tetrahedron
2010, 66, 4029-4031; (b) Li, D.; Yin, K.; Li, J.; Jia, X.
Tetrahedron Lett. 2008, 49, 5918-5919.
7.
Nishihara, Y.; Ikegashira, K.; Hirabayashi, K.; Ando, J.; Mori,
A.; Hiyama, T. J. Org. Chem. 2000, 65, 1780-1787.
8. Nishihara, Y.; Ikegashira, K.; Mori, A.; Hiyama, T.
Tetrahedron Lett. 1998, 39, 4075-4078.
This study is in continuation of our ongoing research
interest using 1,1-dibromoalkenes. Here, we have developed
an easy and practicable method for the synthesis of 1,3-diynes
through a domino dehydrobromination and homocoupling
sequence in a one-pot operation. This method is significant for
the following reasons; (i) this is a copper-free protocol using
Pd-conditions which effectively alienates the formation of 1,1-
diynyl-1-alkene as side product, (ii) the two protocols
disclosed utilize routinely used Pd(PPh3)4 with low catalyst
loadings and (iii) functional group tolerance in terms of
chemo-selectivity was achieved and (iv) presence of reactive
halo group in the product is useful for further
functionalizations.
9. (a) Osowska, K.; Lis, T.; Szafert, S. Eur. J. Org. Chem. 2008,
4598-4606; (b) Chen, Z.; Jiang, H.; Wang, A.; Yang, S. J. Org.
Chem. 2010, 75, 6700-6703.
10. Singh, F. V.; Amaral, M. F. Z. J.; Stefani, H. A. Tetrahedron
Lett. 2009, 50, 2636-2639.
11. Chelucci, G. Chem. Rev. 2012, 112, 1344-1462 and references
cited therein.
12. (a) Corey, E. J.; Fuchs, P. L. Tetrahedron Lett. 1972, 13, 3769-
3772; (b) Ramirez, F.; Desai, N. B.; Mckelvie, N. J. Am.
Chem. Soc. 1962, 84, 1745-1747.
13. (a) Coste, A.; Couty, F.; Evano, G. Synthesis 2010, 1500-1504;
(b) Suzuki, H.; Aihara, M; Yamamoto, H.; Takamoto, Y.;
Ogawa, T. Synthesis 1988, 236-238.
14. Hui, J.; Chunxiang, K. Chin. J. Chem. 2011, 29, 592-594.
15. Yan, J.; Wang, L. Synth. Commun. 2005, 35, 2333-2338.
16. Vanderesse, R.; Fort, Y.; Becker, S.; Caubere, P. Tetrahedron
Lett. 1986, 27, 3517-3520.
Overall, the present methodology of in situ generation of 1-
bromoalkyne and its reductive coupling towards the
preparation of symmetrical 1,3-diyne using Cu-free Pd-
catalyzed conditions is a straightforward domino approach
using 1,1-dibromoalkenes. The synthetic protocol developed
may serve as an excellent synthetic alternative avoiding the
direct use of terminal alkynes or functionalized alkynes in the
preparation of 1,3-diynes.
17. Galamb, V.; Gopal, G.; Alper, H. Organometallics 1983, 2,
801-805.
18. Shen, W.; Thomas, S. A. Org. Lett. 2000, 2, 2857-2860.
19. Rao, M. L. N.; Jadhav, D. N.; Dasgupta, P. Org. Lett. 2010, 12,
2048-2051.
20. (a) Rao, M. L. N.; Dasgupta, P. Tetrahedron Lett. 2012, 53,
162-165; (b) Rao, M. L. N.; Jadhav, D. N.; Dasgupta, P. Eur. J.
Org. Chem. 2013, 781-788.
21. Representative coupling procedure (Table 2): A mixture of 1-
(2,2-dibromovinyl)-4-methylbenzene (0.207 g, 0.75 mmol, 1
equiv.), K3PO4 (0.48 g, 2.25 mmol, 3 equiv.), pyridine (0.03 g,
0.375 mmol, 0.5 equiv.), Pd(PPh3)4 (0.017 g, 0.015 mmol, 0.02
equiv.) and NMP (5 mL) were heated at 90 oC for 2 hours in an
oven-dried 50 mL Schlenk tube under nitrogen atmosphere.
The contents were cooled to room temperature, quenched with
water and extracted with ethyl acetate. The combined extract
was treated with brine followed by anhydrous MgSO4 and
concentrated. The crude was purified by column
chromatography using silica gel and petroleum ether as eluent,
to isolate 2.1 in 88% yield (0.076 g). . Isolated yields are
calculated considering 0.375 mmol of the product as 100%
yield.
Acknowledgments
It is our pleasure to thank the Council of Scientific and
Industrial Research (CSIR), New Delhi for supporting this
work (No. 02(0091)/12/EMR-II). P. D., B. S. R and V. N. M
acknowledge the research fellowships received from CSIR,
New Delhi.
Supplementary data
Supplementary data comprising 1H and 13C NMR, HRMS, IR
for all the 1,3-diyne products (2.1-2.17) was given and it can
be found in the online version.
22. Shen, W.; Wang, L. J. Org. Chem. 1999, 64, 8873-8879.
23. (a) Everson, D. A.; Jones, B. A.; Weix, D. J. J. Am. Chem. Soc.
2012, 134, 6146-6159; (b) Pri-Bar, I.; Alper, H. J. Org. Chem.
1989, 54, 36-38.
24. Coupling conditions for Table 4: The procedure given in ref.
21 was followed with reaction conditions involving 1,1-
dibromoalkene (0.75 mmol, 1 equiv.), K3PO4 (2.25 mmol, 3
equiv.), n-Bu4NI (0.075 mmol, 0.1 equiv.), Pd(PPh3)4 (0.015
mmol, 0.02 equiv.) and NMP (5 mL), 90 oC, 5 h. All the
products 2.1-2.17 and were identified by 1H, 13C NMR, EI-MS
or ESI-MS and IR spectroscopic methods.
References and notes
1. (a) Siemsen, P.; Livingston, R. C.; Diederich, F. Angew. Chem.
Int. Ed. 2000, 39, 2632-2657; (b) Shun, A. L. K. S.;
Tykwinsky, R. R. Angew. Chem. Int. Ed. 2006, 45, 1034-1057.
2. (a) Liu, J.; Lam, J. W. Y.; Tang, B. Z. Chem. Rev. 2009, 109,
5799-5867; (b) Arakawa, Y. ; Nakajima, S.; Kang, S.; Konishi,
G.; Watanabe, J. J. Mater. Chem. 2012, 22, 14346-14348; (c)
Tour, J. M. Chem. Rev. 1996, 96, 537-554; (d) Martin, R. E.;
Diederich, F. Angew. Chem. Int. Ed. 1999, 38, 1350-1377.
3. (a) Chen, J.; Liu, Y. Tetrahedron Lett. 2008, 49, 6655-6658; (b)
Singha, R.; Nandi, S.; Ray, J. K. Tetrahedron Lett. 2012, 53,
6531-6534.
25. (a) Weng, Y.; Cheng, B.; He, C.; Lei, A. Angew. Chem. Int. Ed.
2012, 51, 9547-9551; (b) Jaksic, B. E.; Jiang, J.; Fraser, A. W.;
Baird, M. C. Organometallics 2013, 32, 4192-4198.