- Interactions in Crystals: The Dimorphism of (2-Pyridyl)(2-pyrimidyl)amine
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Preceding structural studies of 2-aminopyridine derivatives prove that they form polymorphic H-pair-bonded dimers, and, therefore, (2-pyridyl)(2-pyrimidyl)amine has been crystallized under different conditions. Two different monoclinic modifications are characterized by their crystal structures of the same space group P21/c: form I exhibits the well known herringbone motif and form II the sandwich-herringbone one. Both modifications contain almost identical planar, H-pair-bridged molecular dimers. Crystals of form I are readily obtained from any solvent, whereas those of form II result either on fast evaporation of a Et2O solution or by resolidification of the melt. Differential thermal analysis (DTA) and crystallization experiments at different temperatures prove, for both modifications, no transitions in the temperature range between -25° and the melting point at 152° and, therefore, the system should be monotropic. The structural and thermodynamic aspects of the (2-pyridyl)(2-pyrimidyl)amine dimorphism are discussed in comparison to those of the trimorphism observed for di(2-pyridyl)amine.
- Bock, Von Hans,Sch?del, Holger,N?ther, Christian,Butensch?n, C.N. Frauke
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- Buchwald-Hartwig Amination of Coordinating Heterocycles Enabled by Large-but-Flexible Pd-BIAN-NHC Catalysts**
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A new class of large-but-flexible Pd-BIAN-NHC catalysts (BIAN=acenaphthoimidazolylidene, NHC=N-heterocyclic carbene) has been rationally designed to enable the challenging Buchwald-Hartwig amination of coordinating heterocycles. This robust class of BIAN-NHC catalysts permits cross-coupling under practical aerobic conditions of a variety of heterocycles with aryl, alkyl, and heteroarylamines, including historically challenging oxazoles and thiazoles as well as electron-deficient heterocycles containing multiple heteroatoms with BIAN-INon (N,N′-bis(2,6-di(4-heptyl)phenyl)-7H-acenaphtho[1,2-d]imidazol-8-ylidene) as the most effective ligand. Studies on the ligand structure and electronic properties of the carbene center are reported. The study should facilitate the discovery of even more active catalyst systems based on the unique BIAN-NHC scaffold.
- Li, Dong-Hui,Lan, Xiao-Bing,Song, A-Xiang,Rahman, Md. Mahbubur,Xu, Chang,Huang, Fei-Dong,Szostak, Roman,Szostak, Michal,Liu, Feng-Shou
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supporting information
(2021/12/06)
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- Sequential amination of heteroaromatic halides with aminopyridine 1-oxides and their N-protected derivatives based on novel aza-Smiles rearrangement
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The SNAr and Pd-catalyzed amination of chloro derivatives of azines, diazines, and triazines with 2-aminopyridine 1-oxides and their N-protected derivatives was described.
- Wolinska, Ewa
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p. 227 - 232
(2013/05/09)
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- SYNTHESIS AND PROPERTIES OF DIHETERYLAMINES
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Methods are described for the preparation of secondary heterocyclic amines containing a pyridine nitrogen atom in the α position relative to the amino group.Compounds of this class were prepared: a) from α-hetaryl halides and α-hetarylamines in presence of barium oxide ( the process is accompanied by intramolecular cyclization, leading to the formation of condensed imidazoles); b) by the cyclization of heterylthioureas with a bromo acetal; c) by the reactions of 2-(methylthio)benzindole hydiodide with α-heterylamines.Secondary heterylamines containing a benzindole system exist in the imino form.
- Kaplan, G. M.,Frolov, A. N.,El'tsov, A. V.
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p. 177 - 182
(2007/10/02)
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