- Electrochemical coupling of mono and dihalopyridines catalyzed by nickel complex in undivided cell
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One step nickel-catalyzed electroreductive homocoupling among 2-bromopicolines and 2-bromopyridine has been investigated by our group in an undivided cell and using zinc or iron as sacrificial anode. In this work, it was developed mono and dihalopyridines coupling to obtain possible products from heterocoupling. A series of reactions were carried out in order to develop a synthetic method for the preparation of unsymmetrical 2,2′-bipyridines and 2,2′:6′,2″-terpyridines. Statistical yields (50%) were observed for 2-bromopyridines/2-bromo-6-methylpyridine heterocoupling. In a preliminary study devoted to terpyridines preparation, good results were obtained for 2,6-dihalopyridines homocoupling, affording 2,6-dichloro-2, 2′-bipyridine (46%) and 2,6-dibromo-2,2′-bipyridine (56%), at controlled reaction time. At major reaction time, it was observed that the direct electroreduction of the 2,6′-dihalo-2,2′-bipyridines intermediates and 2,6″-dihalo-2,2′:6′,2″-terpyridines products on the cathode surface. A reasonable isolated product yield of 6,6″-dimethyl-2,2′:6′,2″-terpyridine (10%) was only observed in the reaction between 2,6-dichloropyridine and 2-bromo-6- methylpyridine (1:2).
- Oliveira, Jadson L.,Silva, Maria J.,Florêncio, Tupolevck,Urgin, Karne,Sengmany, Stéphane,Léonel, Eric,Nédélec, Jean-Yves,Navarro, Marcelo
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experimental part
p. 2383 - 2390
(2012/04/17)
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- A novel one-pot synthesis of 6,6''-dibromo-2,2': 6'2''-terpyridine
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Dibromo-2,2': 6'2''-terpyridine was obtained in a moderate yield by lithiation of four molar amounts of 2,6-dibromopyridine with butyllithium followed by treatment with phosphorus trichloride in diethyl ether.
- Uchida,Okabe,Kobayashi,Oae
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p. 939 - 940
(2007/10/02)
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- Preparation of Dipyridylmethane Ligands with Pseudo-C2 Symmetry. Grafting on Polystyrenes via Transformation to Phenolic Derivatives
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Efficient grafting of dipyridylmethane ligands on highly cross-linked as well as gel-type chloromethylated polystyrenes has been achieved using phenolic derivatives of the ligands.In this way, chiral polymer-supported ligands with pseudo-C2 symmetry were obtained.The synthesis of the ligands and their grafting under mild conditions are described, as well as the preparation of monomeric models.During reduction of 6,6'-(2,2-dimethyl-1-oxopropyl) derivatives with sodium borohydride, the R,S isomers were unexpectedly formed with high selectivity.
- Levacher, Vincent,Moberg, Christina
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p. 1755 - 1762
(2007/10/02)
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