33777-92-3Relevant academic research and scientific papers
Electrochemical coupling of mono and dihalopyridines catalyzed by nickel complex in undivided cell
Oliveira, Jadson L.,Silva, Maria J.,Florêncio, Tupolevck,Urgin, Karne,Sengmany, Stéphane,Léonel, Eric,Nédélec, Jean-Yves,Navarro, Marcelo
experimental part, p. 2383 - 2390 (2012/04/17)
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).
Effect of guest molecules, metal ions and linker length on the assembly of chiral metallomacrocycles: solution studies and crystal structures
Houghton, Mark A.,Bilyk, Alexander,Harding, Margaret M.,Turner, Peter,Hambley, Trevor W.
, p. 2725 - 2734 (2007/10/03)
Eight new 2,2'-bipyridines, containing functionalised acetylenes at the 6 position, have been prepared.The azido derivatives were used to prepare three compounds L1, L2 and L3, which contain pyromellitimide spacers connected to 6,6'-bipyridines with propynyl, butynyl and propynyloyl linkers respectively, via iminophosphoranes.In the presence of equimolar amount of zinc(II) triflate (trifluoromethanesulfonate), L1 was assembled exclusively into the chiral metallomacrocycle 12>4- at low concentrations (-3) or in the presence of an aromatic guest molecule S, which stabilises the complex through binding in the cavity of the metallomacrocycle.The crystal structures of diquabis(N,N'-bisnaphthalene-1,8:44,5-tetracarboximide)dizinc tetrakis(triflate) 12>4*H2O, containing either p- or o-dimethoxybenzene bound in the cavity, were determined by X-ray diffraction methods.In both cases the crystals were extremely fragile and there was extensive disorder of substrate and solvate molecules and the triflate counter ions in channels in the lattice.These structures, while of limited quality, confirm the identity of the complexes, and reveal several substrate-dependent differences.Comparison of the two structures provided clear evidence for the metallomacrocycle adjusting its shape and dimensions to accomodate optimum binding of the substrate through ?-stacking/electrostatic interactions, and provides the first example of a metallosupramolecular complex in which the cavity size is determined by the bound substrate.The assembly of the chiral metallomacrocycle was also achieved with L1 and cadmium(II) and L1 and copper(I) in the presence of >20 equivalents of m-dimethoxybenzene.In contrast, L2 and L3 formed zinc(II) complexes which gave only broadened NMR spectra consistent with equilibrating mixtures of oligomers.The different results obtained with L1, L2 and L3 highlight the importance of the rigid propargyl(prop-2-ynyl) linker in directing the outcome of the assembly process.
