Communication
RSC Advances
terminal aryl acetylenes possessing one or even two substitu-
ents at the ortho position of the aromatic ring (Table 2, entries
12–14) clearly indicate that the 1a/3-catalyzed dimerization in
water does not involve agostic interactions between the Pd
centre and the ortho protons of the aromatic ring of the alkyne.3b
Therefore, as recently proposed by Gevorgyan,3e under the
optimized reaction conditions, the dimerization should occur
via a hydropalladation pathway (Scheme 2).
Notes and references
1 (a) B. M. Trost, F. D. Toste and A. B. Pinkerton, Chem. Rev.,
2001, 101, 2067–2096; (b) Modern Acetylene Chemistry, ed. P.
J. Stang and F. Diederich, VCH, New York, 1995; (c)
E. Bustelo and P. H. Dixneuf, in Handbook of CH
Transformations, ed. G. Dyker, Wiley-VCH, Weinheim, 2005,
vol. 1, ch. 2; (d) V. Ritleng, C. Sirlin and M. Pfeffer, Chem.
With respect to the active species involved in the catalytic
cycle, palladacycles have been proposed as a source of highly
active palladium nanoparticles. However, a mercury poisoning
experiment performed on the model reaction (see ESI† for
experimental details), pointed to the participation of other
different catalytically active palladium species, whose identi-
cation is currently performed in our lab.
¨
Rev., 2002, 102, 1731–1769; (e) P. Wessig and G. Muller,
Chem. Rev., 2008, 108, 2051–2063; (f) H. Katayama and
F. Ozawa, Coord. Chem. Rev., 2004, 248, 1703–1715; (g)
C. Janiak, Coord. Chem. Rev., 2006, 250, 66–94; (h)
B. M. Trost and A. McClory, Chem.–Asian J., 2008, 3, 164–
´
194; (i) R. Chinchilla and C. Najera, Chem. Rev., 2014, 114,
1783–1826.
2 (a) N. Weibel, S. Grunder and M. Mayor, Org. Biomol. Chem.,
2007, 5, 2343–2353; (b) K. C. Nicolaou, P. G. Bulger and
D. Sarlah, Angew. Chem., Int. Ed., 2005, 44, 4442–4489; (c)
M. Kivala and F. Diederich, Pure Appl. Chem., 2008, 80,
411–427.
Conclusions
In conclusion, we have optimized a palladium-derived catalytic
system that efficiently mediates the dimerization of function-
alized aromatic alkynes in a highly regio- and stereoselective
manner to afford (E)-1,3-enynes with good yields in water as
solvent being microwave irradiation crucial for this process to
succeed.
3 For representative examples, see: Pd: (a) B. M. Trost,
¨
M. T. Sorum, C. Chan, A. E. Harms and G. Ruhter, J. Am.
Chem. Soc., 1997, 119, 698–708; (b) M. Rubina and
V. Gevorgyan, J. Am. Chem. Soc., 2001, 123, 11107–11108;
(c) C. Yang and S. P. Nolan, J. Org. Chem., 2002, 67, 591–
593; (d) N. Tsukada, S. Ninomiya, Y. Aoyama and Y. Inoue,
Org. Lett., 2007, 9, 2919–2921; (e) C. Jahier,
O. V. Zatolochnaya, N. V. Zvyagintsev, V. P. Ananikov and
V. Gevorgyan, Org. Lett., 2012, 14, 2846–2849; (f) T. Chen,
C. Guo, M. Goto and Li-B. Han, Chem. Commun., 2013, 49,
7498–7500. Ru: (g) M. Bassetti, C. Pasquini, A. Raneri and
D. Rosato, J. Org. Chem., 2007, 72, 4558–4561; (h)
Acknowledgements
Financial support from the MINECO (CTQ2010-20387), the
Generalitat Valenciana (PROMETEO/2009/038), and the
University of Alicante (VIGROB-173, UAUSTI13-01) is acknowl-
edged. We also acknowledge Dr Isidro M. Pastor from Alicante
University for generously providing us ligands 6–9.
´
A. Coniglio, M. Bassetti, S. E. Garcıa-Garrido and
J. Gimeno, Adv. Synth. Catal., 2012, 354, 148–158. Ni: ; (i)
S. Ogoshi, M. Ueta, M. A. Oka and H. Kurosawa, Chem.
Commun., 2004, 2732–2733. Co: (j) S. Ventre, E. Derat,
M. Amatore, C. Aubert and M. Petit, Adv. Synth. Catal.,
2013, 355, 2584–2590. Rh: (k) T. Katagiri, H. Tsurugi,
T. Satoh and M. Miura, Chem. Commun., 2008, 3405–3407;
´
´
(l) L. Rubio-Perez, R. Azpıroz, A. Di Giuseppe, V. Polo,
´
R. Castarlenas, J. J. Perez-Torrente and L. A. Oro, Chem.–
Eur. J., 2013, 19, 15304–15314. Fe: (m) G. C. Midya,
S. Paladhi, K. Dhara and J. Dash, Chem. Commun., 2011,
47, 6698–6700. Zr: (n) R. H. Platel and L. L. Schafer, Chem.
Commun., 2012, 48, 10609–10611. Lu: (o) M. Nishiura,
Z. Hou, Y. Wakatsuki, T. Yamaki and T. Miyamoto, J. Am.
Chem. Soc., 2003, 125, 1184–1185.
4 (a) X. Chen, P. Xue, H. H. Y. Sung, I. D. Williams,
M. Perizzini, C. Bianchini and G. Jia, Organometallics, 2005,
24, 4330–4332; (b) C.-K. Chen, H.-C. Tong, C.-Y. Chen Hsu,
C. Y. Lee, Y. H. Fong, Y.-S. Chuang, Y.-H. Lo, Y.-C. Lin and
Y. Wang, Organometallics, 2009, 28, 3358–3368.
5 Palladacycles: Synthesis, Characterization and Applications, ed.
J. Dupont and M. Pfeffer, Wiley-VCH, Weinheim, 2008.
6 For reviews on the use of oxime-palladacycles as precatalysts
in cross-coupling reactions, see: (a) D. A. Alonso, L. Botella,
Scheme 2 Hydropalladation mechanism for alkyne dimerization.3e
This journal is © The Royal Society of Chemistry 2014
RSC Adv., 2014, 4, 46508–46512 | 46511