The Experts below are selected from a list of 36 Experts worldwide ranked by ideXlab platform
H. C. Van Der Plas - One of the best experts on this subject based on the ideXlab platform.
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An SN(ANRORC) mechanism in the Amination of phenyl-1,3,5-triazine with potassium amide in liquid ammo a A novel mechanism for the Chichibabin reaction†‡
Recueil des Travaux Chimiques des Pays-Bas, 2010Co-Authors: Gy. Simig, H. C. Van Der PlasAbstract:The Amination of phenyl- 1,3,5-triazine with potassium [15N]amide in [15N]ammonia has been investigated at −33°. It was observed that (i) a Chichibabin Amination occurs at a very low rate, (ii) the Amination occurs partly according to an SN(ANRORC) mechanism, (iii) a considerable amount of 15N is present in recovered starting material. All these results are explained by a series of equilibria between substrate ⇄ σ-adducts ⇆ open-chain amidines ⇄ product.
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The Chichibabin Amination of 4-phenyl- and 4-tert-butylpyrimdine
Recueil des Travaux Chimiques des Pays-Bas, 2010Co-Authors: J. Breuker, H. C. Van Der PlasAbstract:During a study on the Amination of 4-phenylpyrimidine in potassium amide/ liquid ammonia it was found that the extent to which the SN(ANRORC) mechanism operates in the Amination largely depends upon whether an ammonium salt is used in quenching the reaction. The composition of the σ-adduct mixture, the structure of the open-chain intermediates, the inhibition of the SN(ANRORC) mechanism and the course of the Amination in apolar solvents have been investigated. In addition, it has been found that, in the Amination of 4-tert-butylpyrimidine, the SN(ANRORC) mechanism occurs to only a very limited extent.
Karl Kirchner - One of the best experts on this subject based on the ideXlab platform.
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2 6 diAmination of substituted pyridines via heterogeneous Chichibabin reaction
Tetrahedron Letters, 2016Co-Authors: Matthias Mastalir, Ernst Pittenauer, Gunter Allmaier, Karl KirchnerAbstract:Abstract A series of ring substituted pyridines were selected for the sodium amide initiated heterogeneous Chichibabin Amination to obtain 2,6-diaminopyridine derivatives which are important synthons for the preparation of PNP pincer ligands. The substrates were treated with an excess of sodium amide in neat mineral oil as solvent under an argon atmosphere. The reaction required temperatures of up to 215 °C under vigorous stirring with an overall reaction time of 3–5 h. In the case of methyl, tert -butyl, phenyl, pyridinyl, and hydroxyl substituted pyridines the desired products were obtained in good to excellent yields (63–96%). Thus, the Chichibabin reaction provides an inexpensive and economic alternative to methodologies starting from halopyridines or pyridine N -oxides provided that the substituents are inert under the harsh reaction conditions.
M. M. El’chaninov - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and reactivity of 2-(2-thienyl)oxazolo[4,5-b]pyridine
Russian Journal of General Chemistry, 2015Co-Authors: A. A. Aleksandrov, M. M. El’chaninovAbstract:Condensation of 2-amino-3-hydroxypyridine with thenoyl chloride in 1-methyl-2-pyrrolidon afforded 2-(2-thienyl)oxazolo[4,5- b ]pyridine. Reactivity of the latter towards electrophilic substitution (nitration, bromination, formylation, acylation) was studied. It is shown that the reaction occurred exclusively at the position 5 of the thiophene ring. Nucleophilic substitution of pyridine ring was performed. Quaternization of 2-(2-thienyl)oxazolo[4,5- b ]pyridine with methyl iodide in benzene was carried out. Chichibabin Amination with an excess of sodium amide in xylene failed.
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Synthesis and properties of 2-(2-furyl)[1,3]oxazolo[4,5-b]pyridine
Russian Journal of Organic Chemistry, 2014Co-Authors: M. M. El’chaninov, A. A. Aleksandrov, E. V. IllenzeerAbstract:The condensation of 2-amino-3-hydroxypyridine with 2-furoyl chloride according to Ladenburg gave 2-(2-furyl)[1,3]oxazolo[4,5- b ]pyridine which was subjected to electrophilic substitution reactions with nitric acid, bromine, hexamethylenetetramine, acetic anhydride, and benzoic acid. In all cases, the electrophile entered exclusively the 5-position in the furan ring. Treatment of the title compound with methyl iodide afforded the corresponding quaternization product at the N^4 atom, whereas no Chichibabin Amination was observed.
Henk C. Van Der Plas - One of the best experts on this subject based on the ideXlab platform.
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oxidative amino dehydrogenation of azines
Advances in Heterocyclic Chemistry, 2004Co-Authors: Henk C. Van Der PlasAbstract:Publisher Summary This chapter reviews the oxidative amino-dehydrogenation reactions. It focuses on reactions in which a substrate reacts with an aminating agent in the presence of an oxidant. This Amination methodology is very useful to replace ring hydrogens in highly electron-deficient azaheterocycles by an amino, alkylamino, dialkylamino, or imino group. Aminations of azines are usually carried out by heating a π-deficient heterocycle with the metal salt of the conjugated base of an amine or amine in an inert, apolar solvent. Chichibabin Amination is the first amino-dehydrogenation reaction. The treatment of pyridine with sodium amide in an inert aprotic solvent at elevated temperatures yields 2-aminopyridine in reasonable yield. The oxidative Amination procedure is simple but varies depending on the structure of the substrate. The oxidative amino-dehydrogenation of monoazines, quinolines, naphthyridines, diazines, quinazolines, quinoxalines, triazines, tetrazines, and their bicyclic analogs is discussed in the chapter. Amination under homogeneous conditions is an important breakthrough in oxidative Amination–dehydrogenation procedures. After addition of the amide ion to the azine, an anionic σ-adduct is formed, which is quite stable in the polar medium as shown by nuclear magnetic resonance (NMR) spectroscopy.
Van Der - One of the best experts on this subject based on the ideXlab platform.
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Oxidative amino-dehydrogenation of azines
2004Co-Authors: Van DerAbstract:This chapter reviews the oxidative amino-dehydrogenation reactions. It focuses on reactions in which a substrate reacts with an aminating agent in the presence of an oxidant. This Amination methodology is very useful to replace ring hydrogens in highly electron-deficient azaheterocycles by an amino, alkylamino, dialkylamino, or imino group. Aminations of azines are usually carried out by heating a π-deficient heterocycle with the metal salt of the conjugated base of an amine or amine in an inert, apolar solvent. Chichibabin Amination is the first amino-dehydrogenation reaction. The treatment of pyridine with sodium amide in an inert aprotic solvent at elevated temperatures yields 2-aminopyridine in reasonable yield. The oxidative Amination procedure is simple but varies depending on the structure of the substrate. The oxidative amino-dehydrogenation of monoazines, quinolines, naphthyridines, diazines, quinazolines, quinoxalines, triazines, tetrazines, and their bicyclic analogs is discussed in the chapter. Amination under homogeneous conditions is an important breakthrough in oxidative Amination–dehydrogenation procedures. After addition of the amide ion to the azine, an anionic σ-adduct is formed, which is quite stable in the polar medium as shown by nuclear magnetic resonance (NMR) spectroscopy