The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Christian Näther - One of the best experts on this subject based on the ideXlab platform.
-
CdX2 Coordination Polymers with 2-Chloropyrazine and 2-Methylpyrazine: Similar Ligands – Similar Structures – Different Reactivity
European Journal of Inorganic Chemistry, 2017Co-Authors: Christian Näther, Inke Jeß, Robert E. Dinnebier, Luzia S. Germann, Michael Braun, Huayna TerraschkeAbstract:Several coordination compounds, based on Cd halides and 2-methylpyrazine (Mepyz) or 2-Chloropyrazine (Clpyz) as N-donor coligands, are synthesized and their crystal structures determined by either single-crystal or X-ray powder diffraction (XRPD). In [CdX2(2-Clpyz)2]n (X = Cl: 1-Cl-Clpyz; X = Br: 1-Br-Clpyz; and X = I: 1-I-Clpyz) and [CdX2(2-Mepyz)2]n (X = Cl: 1-Cl-Mepyz; X = Br: 1-Br-Mepyz; and X = I: 1-I-Mepyz), the Cd cations are octahedrally coordinated by two N-donor ligands and are linked into chains by the halide anions that share common edges. In the ligand-deficient compounds [CdX2(2-methylpyrazine)]n (X = Cl: 2-Cl-Mepyz; X = Br: 2-Br-Mepyz; and X = I: 2-I-Mepyz), similar CdX2 chains, which are connected into layers by the N-donor ligands, are observed. Thermal analysis of all 1-Mepyz compounds shows a transformation into 2-Mepyz, which is not observed for the 2-Chloropyrazine compounds. On further heating, compounds of composition [(CdX2)2(2-Mepyz)]n (X = Cl: 3-Cl-Mepyz; X = Br: 3-Br-Mepyz) and [(CdI2)3(2-Mepyz)2] (4-I-Mepyz) are observed. A discrete complex, with the composition CdI2(2-Mepyz)2 monohydrate (1-I-Mepyz-H2O), and a hydrate with the composition [(CdI2)(2-Mepyz)]·1.5H2O (2-I-Mepyz-H2O) with an unknown structure, were also synthesized. Both lose the water molecules upon heating. Luminescence measurements show blue to orange emissions in the range of ca. 22530–16276 cm–1, depending on the halide or pyrazine substituent, as well as the metal halide/ligand ratio.
-
Synthesis, Thermal and Magnetic Properties of New Coordination Compounds based on Mn(NCS)2 with 2-Chloropyrazine and 2-Methylpyrazine as neutral Co-Ligand†
Zeitschrift für anorganische und allgemeine Chemie, 2013Co-Authors: Susanne Wöhlert, Tomče Runčevski, Robert E. Dinnebier, Christian NätherAbstract:Reaction of manganese(II) thiocyanate with 2-Chloropyrazine leads always to the formation of a compound of composition Mn(NCS)2(2-Chloropyrazine)4 (1-Mn/Cl) that consists of discrete complexes, in which the manganese cation is coordinated by two terminal thiocyanato anions and four 2-Chloropyrazine ligands. In contrast, with 2-methylpyrazine only an aqua complex of composition Mn(NCS)2(2-methylpyrazine)2(H2O)2 (1-Mn/CH3) is obtained that also consists of discrete octahedrally coordinated complexes. Moreover, a few single crystals of Mn(NCS)2(2-Chloropyrazine)4·Mn(NCS)2(2-Chloropyrazine)2(H2O)2·2-Chloropyrazine trisolvate (2-Mn/Cl) and Mn(NCS)2(2-methylpyrazine)2(H2O)2·Mn(NCS)2(H2O)4 (2-Mn/CH3) were accidently obtained but no larger amounts are available. On heating, 1-Mn/Cl and 1-Mn/CH3 transforms into new compounds of composition Mn(NCS)2(L)2 (L = 2-Chloropyrazine) (4-Mn/Cl) and 2-methylpyrazine (3-Mn/CH3). Surprisingly on further heating 1-Mn/CH3 looses additional 2-methylpyrazine ligands and transforms into a new compound of composition Mn(NCS)2(2-methylpyrazine) (4-Mn/CH3). Compound 4-Mn/Cl is isotypic to its cobalt(II) analog and 4-Mn/CH3 is isotypic to Cd(NCS)2(2-methylpyrazine) reported recently and therefore, both structures were refined by the Rietveld method. The crystal structures of both compounds are strongly related. They consists of dimeric units, in which each two manganese cations are linked by pairs of μ-1, 3-bridging thiocyanato anions, which are further connected into layers by single μ-1, 3-bridging anionic ligands. In contrast to 4-Mn/Cl, in 4-Mn/CH3 these layers are further linked into a 3D coordination network by the 2-methylpyrazine ligands. Magnetic measurements reveal that 1-Mn/Cl, 1-Mn/CH3, and 3-Mn/CH3 shows only Curie- or Curie-Weiss paramagnetism, whereas 4-Mn/Cl and 4-Mn/CH3 shows antiferromagnetic ordering at TN = 22.9 K and at 26.5 K. The results of these investigations are compared with those obtained for related compounds.
-
Structures and Magnetic Properties of Nickel Thiocyanato Coordination Compounds with 2‐Chloropyrazine as a Neutral Coligand
European Journal of Inorganic Chemistry, 2013Co-Authors: Susanne Wöhlert, Christian NätherAbstract:Reaction of Ni(NCS)2 with 2-Chloropyrazine in different molar ratios and solvents at room temperature leads to five new coordination polymers. In the crystal structures of Ni(NCS)2(2-Chloropyrazine)4·2-Chloropyrazine solvate (1) and Ni(NCS)2(2-Chloropyrazine)4 (2) the nickel cations are octahedrally coordinated by two terminal N-bonded thiocyanato anions and four 2-Chloropyrazine ligands into discrete complexes. In the crystal structures of the Ni(NCS)2(2-Chloropyrazine)2(CH3OH)2·(CH3OH)2 solvate (3) and Ni(NCS)2(2-Chloropyrazine)2(CH3OH)2 (4) each nickel(II) cation is coordinated by two terminal N-bonded thiocyanato anions, two 2-Chloropyrazine ligands and two O-bonded methanol molecules in a slightly distorted octahedron. On heating, compounds 1 and 2 transform into the ligand-deficient 1:2 compound 5, which can also be crystallized from solution. In the crystal structure of [Ni(NCS)2(2-Chloropyrazine)2]n (5) each nickel(II) cation is coordinated by two N-bonded and two S-bonded thiocyanato anions as well as two 2-Chloropyrazine ligands. The nickel cations are linked into dimers by pairs of μ-1,3-bridging thiocyanato anions that are further linked into chains and finally into layers by single μ-1,3-bridging thiocyanato anions. Magnetic measurements of compound 1 and 2 show only Curie or Curie–Weiss paramagnetism, whereas in the ligand-deficient compound 5 a metamagnetic transition is observed at a critical field of HC = 14 kOe. The results of the magnetic measurements are compared with those of related nickel compounds with different coligands.
-
Synthesis, structures and magnetic properties of new Fe(II) and Co(II) thiocyanato coordination compounds with 2-Chloropyrazine as Co-ligand
Inorganica Chimica Acta, 2013Co-Authors: Susanne Wöhlert, Christian NätherAbstract:Abstract Investigations on the synthesis of coordination compounds based on Fe(NCS)2 and Co(NCS)2 with 2-Chloropyrazine as ligand leads to the formation of five new compounds. Fe(NCS)2(2-Chloropyrazine)4 (1-Fe), Co(NCS)2(2-Chloropyrazine)4 (1-Co) and Fe(NCS)2(2-Chloropyrazine)4·2-Chloropyrazine solvate (2-Fe) consists of discrete complexes in which the metal cations are octahedrally coordinated and in which the thiocyanato anions are only terminal coordinated. On heating 1-Fe and 1-Co transform into new coordination polymers of composition [Fe(NCS)2(2-Chloropyrazine)2]n (3-Fe) and [Co(NCS)2(2-Chloropyrazine)2]n (3-Co) which are isotypic. No access to large and phase pure amounts of these compounds was found in solution but the structure of 3-Co was determined from a crystal obtained in one batch by accident. In the crystal structure of 3-Co and 3-Fe the metal(II) cations are coordinated by two N-bonded as well as two S-bonded thiocyanato anions and two 2-Chloropyrazine ligands and are linked by μ-1,3-bridging anions into layers. Magnetic measurements of 1-Fe and 1-Co show only Curie- or Curie–Weiss paramagnetism, whereas for 3-Fe antiferromagnetic ordering and for 3-Co metamagnetic behavior is observed.
-
Synthesis, Crystal Structure and Thermal Reactivity of [ZnX2(2-Chloropyrazine)] (X = Cl, Br, I) Coordination Compounds
European Journal of Inorganic Chemistry, 2008Co-Authors: Gaurav Bhosekar, Inke Jeß, Nicolai Lehnert, Christian NätherAbstract:Reaction of zinc(II) halides with 2-Chloropyrazine in different solvents leads to the formation of five new coordination compounds that contain either only 2-Chloropyrazine or additional water molecules as donor ligands. In the ligand-rich 1:2 compound catena[bis(2-Chloropyrazine-N)]di-μ-chlorozinc(II) (1) the zinc atom is coordinated by two 2-Chloropyrazine ligands and four chlorine atoms in an octahedral fashion. The zinc atoms are connected by the chloride atoms forming linear chains. In the isotypic ligand-rich 1:2 compounds bis(2-Chloropyrazine-N)dibromozinc(II) (2) and bis(2-Chloropyrazine-N)diiodozinc(II) (3) discrete complexes are found in which each zinc atom is coordinated by two 2-Chloropyrazine ligands and two halide atoms within distorted tetrahedra. The 1:1 compounds aqua-(2-Chloropyrazine-N)dibromozinc(II) (4) and aqua-(2-Chloropyrazine-N)diiodozinc(II) (5) are also isotypic and form discrete complexes in which the zinc atoms are surrounded by two halide atoms, one 2-Chloropyrazine ligand and one water molecule. Upon heating, compounds 1–5 form ligand-deficient 1:1 and 2:1 compounds of composition [ZnX2(2-Chloropyrazine)] (X = halide) and [(ZnX2)2(2-Chloropyrazine)]. X-ray powder diffraction shows that identical ligand-deficient intermediates are obtained on decomposition of either [ZnX2L2] (L = 2-Chloropyrazine) or the [ZnX2L(H2O)] complexes. DFT calculations suggest that the formation of the [ZnX2L(H2O)] complex is energetically favoured for the heavier halide anions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Fabrice Cottet - One of the best experts on this subject based on the ideXlab platform.
-
Silyl‐Mediated Halogen/Halogen Displacement in Pyridines and Other Heterocycles
European Journal of Organic Chemistry, 2002Co-Authors: Manfred Schlosser, Fabrice CottetAbstract:Heating with bromotrimethylsilane converts 2-chloropyridine into 2-bromopyridine and 2-chloro-6-methylpyridine into 2-bromo-6-methylpyridine. Both 2-chloropyridines and 2-bromopyridines give the corresponding iodo compd. when treated with in situ generated iodotrimethylsilane. Although 3- and 4-chloropyridine are completely inert, 2,4-dichloropyridine undergoes the halogen/halogen exchange simultaneously at the 2- and 4-position. Halogen displacement takes place exclusively at the 2-position with 2,3-dichloropyridine and 2,5-dichloropyridine. In agreement with the intermediacy of N-trimethylsilylpyridinium salts as a prerequisite for the occurrence of halogen exchange, neither 2-fluoropyridine and 2-fluoro-6-methylpyridine nor any 2,6-dihalopyridine reacts. Finally, bromine/chlorine and iodine/chlorine substitution can also be accomplished with 2- or 4-chloroquinoline, 1-chloroisoquinoline, 2-chloropyrimidine, chloropyrazine, and 2,3-dichloroquinoxaline as substrates. [on SciFinder (R)]
Li Yu-tao - One of the best experts on this subject based on the ideXlab platform.
-
Synthesis of 3-oxo-3-[3-trifluoromethyl-5,6-dihydro[1,2,4]triazolo[4,3-a] pyrazin-7(8H)-yl]-1-phenylpropan-1-amine
Chemical Research and Application, 2009Co-Authors: Li Yu-taoAbstract:The fused triazole derivatives,which is an important inhibitors of the dipeptidyl peptidase-Ⅳ enzyme(DPP-Ⅳ),can be used for the treatment or prevention of type 2 diabetes.A new fused triazole derivatives of 3-oxo-3-[3-trifluoromethyl-5,6-dihydro[1,2,4]-triazolo[4,3-a]pyrazin-7(8H)-yl]-1-phenylpropan-1-amine was synthesized from 2-Chloropyrazine and benzaldehyde by hydrazinolysis,trifluoroacetylation,cyclization,hydrogenation,condensation and deprotection reaction.The structures of the compound and its intermediates were determined by IR,NMR,and MS.
-
Synthesis and Characterization of 7-(3-amino-3-(4-methoxyphenyl)propanoyl)-3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-α]piperazine
Journal of Nanchang University, 2009Co-Authors: Li Yu-taoAbstract:The fused triazole derivatives,which is an important inhibitors of the dipeptidyl peptidase-Ⅳ enzyme(DPP-Ⅳ inhibitors),can be used for the treatment or prevention of type 2 diabetes.A new fused triazole derivatives of 7-(3-amino-3-(4-methoxyphenyl)propanoyl)-3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4] triazolo[4,3-α]piperazine was synthesized from 2-Chloropyrazine and 4-methoxy-benzaldehyde by hydrazinolysis,trifluoroacetylation,cyclization,hydrogenation,condensation and deprotection reaction.The structures of the titled compound and intermediates were determined by IR,NMR,and MS.
Katarina Kralova - One of the best experts on this subject based on the ideXlab platform.
-
Synthesis and Biological Evaluation of N-Alkyl-3-(alkylamino)-pyrazine-2-carboxamides.
Molecules (Basel Switzerland), 2015Co-Authors: Lucia Semelková, Klára Konečná, Pavla Paterová, Vladimír Kubíček, Jiri Kunes, Lucie Nováková, Jan Marek, Lieve Naesens, Matus Pesko, Katarina KralovaAbstract:A series of N-alkyl-3-(alkylamino)pyrazine-2-carboxamides and their N-alkyl-3-chloropyrazine-2-carboxamide precursors were prepared. All compounds were characterized by analytical methods and tested for antimicrobial and antiviral activity. The antimycobacterial MIC values against Mycobacterium tuberculosis H37Rv of the most effective compounds, 3-(hexylamino)-, 3-(heptylamino)- and 3-(octylamino)-N-methyl-pyrazine-2-carboxamides 14‒16, was 25 μg/mL. The compounds inhibited photosystem 2 photosynthetic electron transport (PET) in spinach chloroplasts. This activity was strongly connected with the lipophilicity of the compounds. For effective PET inhibition longer alkyl chains in the 3-(alkylamino) substituent in the N-alkyl-3-(alkylamino)pyrazine-2-carboxamide molecule were more favourable than two shorter alkyl chains.
-
Substituted amides of pyrazine-2-carboxylic acids, their synthesis and biological activity
2013Co-Authors: Martin Dolezal, Jiri Kunes, Miroslav Miletin, Katarina KralovaAbstract:acid chloride with ring substituted anilines yielded a series of amides, which were tested for their in vitro antimycobacterial, antifungal and photosynthesis-inhibiting activities. The highest antituberculotic activity (72 % inhibition) against Mycobacterium tuberculosis and the highest lipophilicity (log P = 6.85) were shown by the 3,5-bistrifluoromethylphenyl amide of 5-tert-butyl-6-chloropyrazine-2-carboxylic acid (2o). The 3-methylphenyl amides of 6-chloro- and 5-tert-butyl-6-chloro-pyrazine-2-carboxylic acid (2d and 2f) exhibited only a poor in vitro antifungal effect (MIC = 31.25-500 µmol·dm-3) against all strains tested, although the latter was the most active antialgal compound (IC50 = 0.063 mmol·dm-3). The most active inhibitor of oxygen evolution rate in spinach chloroplasts was the (3,5-bis-trifluoromethylphenyl)amide of 6-chloropyrazine-2carboxylic acid (2m, IC50 = 0.026 mmol·dm-3)
-
Full Paper Substituted Pyrazinecarboxamides: Synthesis and Biological Evaluation†
2006Co-Authors: Martin Dolezal, Lukas Palek, Jarmila Vinsova, Vladimir Buchta, Josef Jampilek, Katarina KralovaAbstract:Abstract: Condensation of the corresponding chlorides of some substituted pyrazine-2-carboxylic acids (pyrazine-2-carboxylic acid, 6-chloropyrazine-2-carboxylic acid, 5-tert-butylpyrazine-2-carboxylic acid or 5-tert-butyl-6-chloropyrazine-2-carboxylic acid) with various ring-substituted aminothiazoles or anilines yielded a series of amides. The syntheses, analytical and spectroscopic data of thirty newly prepared compounds are presented. Structure-activity relationships between the chemical structures and the anti-mycobacterial, antifungal and photosynthesis-inhibiting activity of the evaluated compounds are discussed. 3,5-Bromo-4-hydroxyphenyl derivatives of substituted pyrazinecarboxylic acid, 16-18, have shown the highest activity against Mycobacterium tuberculosis H37Rv (54-72 % inhibition). The highest antifungal effect against Trichophyton mentagrophytes, the most susceptible fungal strain tested, was found fo
-
Substituted Pyrazinecarboxamides: Synthesis and Biological Evaluation
MDPI AG, 2006Co-Authors: Katarina Kralova, Lukas Palek, Jarmila Vinsova, Vladimir Buchta, Josef Jampilek, Martin DolezalAbstract:Condensation of the corresponding chlorides of some substituted pyrazine-2-carboxylic acids (pyrazine-2-carboxylic acid, 6-chloropyrazine-2-carboxylic acid, 5-tert-butylpyrazine-2-carboxylic acid or 5-tert-butyl-6-chloropyrazine-2-carboxylic acid) withvarious ring-substituted aminothiazoles or anilines yielded a series of amides. Thesyntheses, analytical and spectroscopic data of thirty newly prepared compounds arepresented. Structure-activity relationships between the chemical structures and the anti-mycobacterial, antifungal and photosynthesis-inhibiting activity of the evaluatedcompounds are discussed. 3,5-Bromo-4-hydroxyphenyl derivatives of substitutedpyrazinecarboxylic acid, 16-18, have shown the highest activity against Mycobacteriumtuberculosis H37Rv (54-72% inhibition). The highest antifungal effect againstTrichophyton mentagrophytes, the most susceptible fungal strain tested, was found for5-tert-butyl-6-chloro-N-(4-methyl-1,3-thiazol-2-yl)pyrazine-2-carboxamide (8, MIC =31.25 μmol·mL-1). The most active inhibitors of oxygen evolution rate in spinachMolecules 2006, 11 243 chloroplasts were the compounds 5-tert-butyl-6-chloro-N-(5-bromo-2-hydroxyphenyl)- pyrazine-2-carboxamide (27, IC50 = 41.9 μmol·L-1) and 5-tert-butyl-6-chloro-N-(1,3- thiazol-2-yl)-pyrazine-2-carboxamide (4, IC50 = 49.5 μmol·L-1)
-
Substituted Amides of Pyrazine-2-carboxylic acids: Synthesis and Biological Activity
MDPI AG, 2002Co-Authors: Katarina Kralova, Jiri Kunes, Miroslav Miletin, Martin DolezalAbstract:Condensation of 6-chloro-, 5-tert-butyl- or 6-chloro-5-tert-butylpyrazine-2-carboxylic acid chloride with ring substituted anilines yielded a series of amides, which were tested for their in vitro antimycobacterial, antifungal and photosynthesis-inhibiting activities. The highest antituberculotic activity (72% inhibition) against Mycobacterium tuberculosis and the highest lipophilicity (log P = 6.85) were shown by the 3,5-bistrifluoromethylphenyl amide of 5-tert-butyl-6-chloropyrazine-2-carboxylic acid (2o). The 3-methylphenyl amides of 6-chloro- and 5-tert-butyl-6-chloro-pyrazine-2-carboxylic acid (2d and 2f) exhibited only a poor in vitro antifungal effect (MIC = 31.25-500 μmol·dm-3) against all strains tested, although the latter was the most active antialgal compound (IC50 = 0.063 mmol·dm-3). The most active inhibitor of oxygen evolution rate in spinach chloroplasts was the (3,5-bis-trifluoromethylphenyl)amide of 6-chloropyrazine-2-carboxylic acid (2m, IC50 = 0.026 mmol·dm-3)
Manfred Schlosser - One of the best experts on this subject based on the ideXlab platform.
-
Silyl‐Mediated Halogen/Halogen Displacement in Pyridines and Other Heterocycles
European Journal of Organic Chemistry, 2002Co-Authors: Manfred Schlosser, Fabrice CottetAbstract:Heating with bromotrimethylsilane converts 2-chloropyridine into 2-bromopyridine and 2-chloro-6-methylpyridine into 2-bromo-6-methylpyridine. Both 2-chloropyridines and 2-bromopyridines give the corresponding iodo compd. when treated with in situ generated iodotrimethylsilane. Although 3- and 4-chloropyridine are completely inert, 2,4-dichloropyridine undergoes the halogen/halogen exchange simultaneously at the 2- and 4-position. Halogen displacement takes place exclusively at the 2-position with 2,3-dichloropyridine and 2,5-dichloropyridine. In agreement with the intermediacy of N-trimethylsilylpyridinium salts as a prerequisite for the occurrence of halogen exchange, neither 2-fluoropyridine and 2-fluoro-6-methylpyridine nor any 2,6-dihalopyridine reacts. Finally, bromine/chlorine and iodine/chlorine substitution can also be accomplished with 2- or 4-chloroquinoline, 1-chloroisoquinoline, 2-chloropyrimidine, chloropyrazine, and 2,3-dichloroquinoxaline as substrates. [on SciFinder (R)]