Topic
Pyridine
About: Pyridine is a research topic. Over the lifetime, 39783 publications have been published within this topic receiving 561908 citations. The topic is also known as: azabenzene & azine.
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TL;DR: A review of the catalytic activity of metal complexes of binaphthyl compounds and their combinations with salen Schiff base is presented in this paper, where the pyridyl bis (imide) and pyridine bis(imine) complexes of cobalt(II), iron(II) ions have been used as catalysts in the polymerization of ethylene and propylene.
1,237 citations
TL;DR: A reaction in which primary amines are directly acylated by equimolar amounts of alcohols to produce amides and molecular hydrogen in high yields and high turnover numbers is reported.
Abstract: Given the widespread importance of amides in biochemical and chemical systems, an efficient synthesis that avoids wasteful use of stoichiometric coupling reagents or corrosive acidic and basic media is highly desirable. We report a reaction in which primary amines are directly acylated by equimolar amounts of alcohols to produce amides and molecular hydrogen (the only products) in high yields and high turnover numbers. This reaction is catalyzed by a ruthenium complex based on a dearomatized PNN-type ligand [where PNN is 2-(di-tert-butylphosphinomethyl)-6-(diethylaminomethyl)pyridine], and no base or acid promoters are required. Use of primary diamines in the reaction leads to bis-amides, whereas with a mixed primary-secondary amine substrate, chemoselective acylation of the primary amine group takes place. The proposed mechanism involves dehydrogenation of hemiaminal intermediates formed by the reaction of an aldehyde intermediate with the amine.
1,098 citations
TL;DR: The synthesis of 4-dialkylaminopyridines can be accomplished in two steps starting from pyridine as discussed by the authors, and these derivatives are approximately 104 times more active when used as acylation catalysts.
Abstract: The synthesis of 4-dialkylaminopyridines can be accomplished in two steps starting from pyridine. Compared to pyridine, these derivatives are approximately 104 times more active when used as acylation catalysts. Dialkylaminopyridines are being used with ever-increasing frequency for acylation reactions which proceed either incompletely or not at all in pyridine. This article reviews the various possible applications of 4-dialkylaminopyridines in terpene, steroid, carbohydrate and nucleoside chemistry as well as in the transformation of amino acids into α-acyl aminoketones and polymerization of isocyanates. In addition, N-substituted 4-dialkylaminopyridinium salts can be used for the transfer of sensitive groups to nucleophiles in aqueous medium. The exceptional catalytic effect of these derivatives, even in non-polar solvents, is due, in part, to the formation of high concentrations of N-acylpyridinium salts which are present in solution as loosely-bound, highly reactive ion pairs.
1,007 citations
TL;DR: In this article, the same authors compared their results with available data on arene exchange in arenetricarbonylchromium complexes and discussed in terms of electronic and steric effects on metal-arene bonding.
Abstract: Arenedi-µ-chloro-ruthenium complexes [RuCl2(arene)]2 have been prepared by dehydrogenation of the appropriate cyclohexa-1,3-diene or cyclohexa-1,4-diene with ethanolic ruthenium(III) trichloride. They react with ligands (L) such as pyridine, tertiary phosphines, or tertiary arsines to give monomeric complexes [RuCl2(arene)L], which are formally analogous to the arenetricarbonylchromium complexes. Analogous dibromo-, di-iodo-, halogeno-(methyl), and dimethyl derivatives have also been prepared; the latter are thermally unstable and air-sensitive. Reaction of the complexes [RuCl2(arene)]2(arene = benzene or p-cymene) with water gives binuclear tri-µ-chloro-cationic species [Ru2C13(arene)2]+, and reaction with silver(I) tetrafluoroborate in acetonitrile gives monomeric [Ru(arene)(MeCN)3]2+. I.r. and n.m.r. data for the new complexes are given. The complexes [RuCl2(arene)L](L = PBun3 or PPh3) undergo partial or complete arene exchange on heating or on u.v. irradiation in an aromatic solvent, co-ordinated p-cymene being the most easily displaced. The exchange method can be used to prepare hexamethylbenzene complexes, e.g.[RuCl2(C6Me6)(PBun3)]. The results are compared with available data on arene exchange in arenetricarbonylchromium complexes and discussed in terms of electronic and steric effects on metal–arene bonding.
939 citations
728 citations