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Electrochemical coupling of mono and dihalopyridines catalyzed by nickel complex in undivided cell
Authors:Jadson L. Oliveira  Maria J. Silva  Tupolevck Florêncio  Karène Urgin  Stéphane Sengmany  Eric Léonel  Jean-Yves Nédélec  Marcelo Navarro
Affiliation:1. Departamento de Química Fundamental, Universidade Federal de Pernambuco, CCEN, 50670-901 Recife-PE, Brazil;2. Equipe Electrochimie et Synthèse Organique, Institut de Chimie et des Matériaux Paris-Est UMR 7182 CNRS-Université Paris-Est Créteil Val de Marne, 2 rue Henri Dunant, B.P. 28, 94320 Thiais, France
Abstract: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).
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