Letter
NJC
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2 (a) J. Campora, J. A. Lopez, P. Palma, D. del Rio, E. Carmona,
aromatic protons. The signals observed at 4.81 and 4.04 ppm are
in a ratio of 2 : 3, attributed to the methylene and methyl groups,
respectively. Finally, the broad signal observed at 4.11 ppm is
attributed to the OH group. In the 13C{1H} NMR spectrum the
resonance signals observed at 64.04 and 53.35 ppm are assigned
to the CH2 and CH3 groups, respectively. Later, the reaction
between 2-BrPy and 2-Br-6-(C3H5O2)-Py gives the expected
coupling product [6-(1,3-dioxolan-2-yl)-2,20-bipyridine] (17) plus
11 and [6,60-di(1,3-dioxolan-2-yl)-2,20-bipyridine] (18) species
P. Valerga, C. Graiff and A. Tiripicchio, Inorg. Chem., 2001, 40,
4116–4126; (b) J. Campora, E. Gutierrez-Puebla, J. A. Lopez,
A. Monge, P. Palma, D. del Rıo and E. Carmona, Angew. Chem.,
Int. Ed., 2001, 40, 3641–3644; (c) J. Campora, P. Palma, D. del
Rıo, J. A. Lopez, E. Alvarez and N. G. Connelly, Organometallics,
2005, 24, 3624–3628; (d) J. Campora, P. Palma, D. del Rıo,
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J. A. Lopez and P. Valerga, Chem. Commun., 2004, 1490–1491;
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(e) J. Campora, P. Palma, D. del Rıo, E. Carmona, C. Graiff and
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A. Tiripicchio, Organometallics, 2003, 22, 3345–3347.
(ratio 1 : 3 : 2) (entry 4). The analysis of the H NMR spectrum
3 (a) J. M. Racowski, J. B. Gary and M. S. Sanford, Angew. Chem.,
Int. Ed., 2012, 51, 3414–3417; (b) F. Qu, J. R. Khusnutdinova,
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of 17 shows multiple signals from 8.61 to 7.20 ppm assigned to
the aromatic protons of the pyridine ring (7H). Finally, the
reaction involving 2-Br-6-COH-Py and 2-Br-6-(C3H5O2)-Py com-
pounds gives the asymmetric [6-(1,3-dioxolan-2-yl)-60-methoxy-
2,20-bipyridine] (19) and the symmetric species 12 and 18.
In conclusion, through our experimental results, we have
demonstrated that palladacycle I reacts with BrPy at room
temperature, via oxidative addition of the Csp2–Br bond to get
a plausible Pd(IV) complex (Pd-Int1), where the COD auxiliary
ligand and the solvent play a crucial role in the reaction pathway.
The formation of compound 1a took place after a Csp2–Csp2
reductive elimination between the neophyl and pyridyl fragments.
1a evolved in two competitive reaction paths into: (i) the expected
seven-membered palladacycle 1 and (ii) the unexpected bipyridine
complex [Pd(BiPy)Br2]. Furthermore, the substitution of a pyridine
ring with electron-donating or -withdrawing groups did not affect
the pathway of the Csp2–Br bond activation as demonstrated by
the formation of a small library of seven-membered palladacycles
(2–8). Finally, our efforts to get a catalytic system allowed us to
obtain a few asymmetric bipyridine species.
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6 J. Nicasio-Collazo, E. Alvarez, J. C. Alvarado-Monzon, G. Andreu-
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Conflict of interest
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7 (a) C. Tejel, M. P. del Rıo, M. A. Ciriano, E. J. Reijerse,
There are no conflicts to declare.
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F. Hartl, S. Zalis, D. G. H. Hetterscheid, N. Tsichlis i Spithas
and B. de Bruin, Chem. – Eur. J., 2009, 15, 11878–11889;
(b) O. Serrano, J. Nicasio-Collazo, G. Morales, J. C. Alvarado-
Acknowledgements
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Monzon, A. Torres-Huerta, H. Hopfl, J. A. Lopez and A. C.
Esqueda, Organometallics, 2014, 33, 2561–2564; (c) L. A. Berben,
B. de Bruin and A. F. Heyduk, Chem. Commun., 2015, 51,
1553–1554; (d) H. Li, G. A. Grasa and T. J. Colaco, Org. Lett.,
2010, 12, 3332–3335; (e) W. N. O. Wylie, A. J. Lough and R. H.
Morris, Organometallics, 2010, 29, 570–581; ( f ) K. Butsch,
S. Elmas, N. Sen Gupta, R. Gust, F. Heinrich, A. Klein, Y. von
Mering, M. Neugebauer, I. Ott, M. Schafer, H. Scherer and
T. Schurr, Organometallics, 2009, 28, 3906–3915; (g) A. Klein,
A. Dogan, M. Feth and H. Bertagnolli, Inorg. Chim. Acta, 2003,
343, 189–201.
J. N.-C. is grateful to the CONACYT for a Doctoral Fellowship
(No. 229119). O. S. is grateful to the Universidad de Guanajuato
(DAIP-UG-090-2013, Excelencia Academica 2015), SEP-UGTO
(NPTC-270) and FOMIX (GTO-2012-C04-195264) for partial sup-
port to carry out this research. The authors thank the Laboratorio
Nacional UG-CONACYT.
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Notes and references
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