- The reaction of enaminones with carboxamidines: A convenient route for the synthesis of polyaza heterocycles
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A simple and efficient synthetic method to polyaza heterocyclic structures containing 1,3-pyrimidine units has been developed. It is based on the reaction of the enaminones such as 5, 7 and 9 with the appropriate carboxamidines under basic conditions. By this procedure several new polyaza heterocycles have been prepared in good yields.
- Bejan,Ait Haddou,Daran,Balavoine
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- Indolizines and pyrrolo[1,2-c]pyrimidines decorated with a pyrimidine and a pyridine unit respectively
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The three possible structural isomers of 4-(pyridyl)pyrimidine were employed for the synthesis of new pyrrolo[1,2-c]pyrimidines and new indolizines, by 1,3-dipolar cycloaddition reaction of their corresponding N-ylides generated in situ from their corresp
- Popa, Marcel Mirel,Georgescu, Emilian,Caira, Mino R.,Georgescu, Florentina,Draghici, Constantin,Stan, Raluca,Deleanu, Calin,Dumitrascu, Florea
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- Mechanistic Studies on Ruthenium(II)-Catalyzed Base-Free Transfer Hydrogenation Triggered by Roll-Over Cyclometalation
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The synthesis of 2-substituted pyridine–pyrimidine ligands and their complexation with arene ruthenium(II) chloride moieties is reported. Depending on the electronic and steric influences of the ligand, the catalysts undergo CH activation by roll-over cyclometalation. This process opens up the route to the catalytic transfer hydrogenation of ketones with isopropanol as the hydrogen source under base-free and mild conditions. Barriers related to the roll-over cyclometalation process can be determined experimentally by collision-induced dissociation ESI mass spectrometry. They are supported by DFT calculations and allow the classification of the ligands according to their electronic and steric properties, which is also in accordance with critical bond parameters derived from X-ray structure data. DFT calculations furthermore reveal that the formation of a ruthenium(II) hydrido species is plausible through β-hydride elimination from isopropanol.
- Kerner, Christian,Lang, Johannes,Gaffga, Maximilian,Menges, Fabian S.,Sun, Yu,Niedner-Schatteburg, Gereon,Thiel, Werner R.
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p. 212 - 224
(2017/03/07)
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- Study of the coordination and solution structures for the interaction systems between diperoxidovanadate complexes and 4-(pyridin-2-yl)pyrimidine-like ligands
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To understand the substitution effects of 4-(pyridin-2-yl)pyrimidine (pprd) on the coordination reaction equilibria, the interactions between a series of the pprd-like ligands and [OV(O2)2(H2O)] - or [OV(O2)2(HOD)]- or [OV(O 2)2(D2O)]- (bpV) have been explored by a combination of multinuclear (1H, 13C, and 51V) magnetic resonance, heteronuclear single quantum coherence (HSQC) and variable temperature NMR in a 0.15 mol L-1 NaCl D 2O solution that mimics physiological conditions. The direct NMR data are reported for the first time. Competitive coordination interactions result in a series of new hepta-coordinated peroxidovanadate species [OV(O 2)2LL′]- (LL′ = pprd-like chelating ligands). The equilibrium constants for the products between bpV and the pprd-like ligands show that the relative affinity of the ligands is pprd ≈ 2-NH2-pprd > 2-Me-pprd > 2-Et-pprd > 4-(6-methylpyridin-2- yl)pyrimidine (abbr. 6′-Me-pprd). When the ligand is pprd, a pair of isomers (Isomer A and B) are observed in aqueous solution, which are attributed to the different types of coordination modes between the metal and the ligands, while the crystal structure of NH4[OV(O2) 2(pprd)]·2H2O has the same coordination structure as Isomer A. For substituted pprd ligands, however, only one type of structure (Isomer A or B) is observed in solution. These results demonstrate that, when the aromatic ring has a substitution group, both the steric effect (from the alkyl) and hydrogen bonding (from the amine) can affect the coordination reaction equilibrium to prevent the appearance of either Isomer B in solution for the ligands 2-Me-pprd, 2-NH2-pprd, 2-Et-pprd, or Isomer A in solution for 6′-Me-pprd. The Royal Society of Chemistry 2012.
- Yu, Xian-Yong,Yi, Ping-Gui,Ji, Dan-Hong,Zeng, Bi-Rong,Li, Xiao-Fang,Xu, Xin
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supporting information; experimental part
p. 3684 - 3694
(2012/05/07)
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- Highly active and recyclable silica gel-supported palladium catalyst for mild cross-coupling reactions of unactivated heteroaryl chlorides
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Silica gel-supported β-ketoiminatophosphane-Pd complex (Pd@SiO 2) was shown to be a highly active and long-lived catalyst for aqueous Suzuki, Stille and Sonogashira coupling reactions of heteroaryl chlorides. A wide range of heteroaryl chlorides could be efficiently coupled with different nucleophilic partners in the presence of only 0.5 mol% catalyst and under mild conditions. This is one of the most powerful heterogeneous catalysts for the couplings of diverse heteroaryl chlorides. Furthermore, the catalyst could be reused with almost consistent activity. The Royal Society of Chemistry 2010.
- Lee, Dong-Hwan,Jung, Ji-Young,Jin, Myung-Jong
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experimental part
p. 2024 - 2029
(2011/02/22)
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- Deprotonative metalation of substituted benzenes and heteroaromatics using amino/alkyl mixed lithium-zinc combinations
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Different homoleptic and heteroleptic lithium-zinc combinations were prepared, and structural elements obtained on the basis of NMR spectroscopic experiments and DFT calculations. In light of their ability to metalate anisole, pathways were proposed to justify the synergy observed for some mixtures. The best basic mixtures were obtained either by combining ZnCl 2·TMEDA (TMEDA = N,N,N',N'tetramethylethylenediamine) with [Li(tmp)] (tmp = 2,2,6,6-tetramethylpiperidino; 3 equiv) or by replacing one of the tmp in the precedent mixture with an alkyl group. The reactivity of the aromatic lithium zincates supposedly formed was next studied, and proved to be substrate-, base-, and electrophile-dependent. The aromatic lithium zincates were finally involved in palladium-catalyzed cross-coupling reactions with aromatic chlorides and bromides.
- Snegaroff, Katia,Komagawa, Shinsuke,Chevallier, Floris,Gros, Philippe C.,Golhen, Stephane,Roisnel, Thierry,Uchiyama, Masanobu,Mongin, Florence
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experimental part
p. 8191 - 8201
(2010/09/11)
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- Synthesis of a novel series of 6,6′-disubstituted 4,4′-bipyrimidines by radical anion coupling: New π-accepting ligands for coordination chemistry
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A new family of 6,6′-disubstituted 4,4′-bipyrimidine ligands has been prepared and characterized. The reduction potentials of the new ligands, as determined by cyclic voltammetry, indicate that these new ligands are considerably better π-acceptors than the ubiquitous 2,2′-bipyridine ligand, and are even superior to the parent unsubstituted 4,4′- bipyrimidine ligand. The substituents in 6,6′ positions of the 4,4′-bipyrimidine also cause a red-shift in the π→π* and n→π* absorptions throughout the UV region. The X-ray crystal structure of one member of the family of bipyrimidines demonstrates that the aryl substituents may lie coplanar with the pyrimidine rings in the solid state. The additional electron delocalization afforded by the aryl substituents on the pyrimidine rings contribute to the better π-accepting ability of these compounds. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
- Ioachim, Elena,Medlycott, Elaine A.,Polson, Matthew I. J.,Hanan, Garry S.
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p. 3775 - 3780
(2007/10/03)
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- Synthesis of pyrimidines from ketones using microwave irradiation
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A simple, high yielding synthesis of pyrimidines from ketones in the presence of HMDS and formamide is described. Under microwave irradiation, heteroaromatic, aryl, aliphatic, and cyclic ketones cyclized to give pyrimidines in good yields.
- Tyagarajan, Sriram,Chakravarty, Prasun K.
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p. 7889 - 7891
(2007/10/03)
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- Novel synthesis of bihetaryl compounds
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The ring transformation of nitropyrimidinone 1 with acetophenone derivatives 2 affords two kinds of azaheterocyclic compounds, 4-phenylpyrimidines 3 and 3-nitro-6-phenyl-2-pyridones 4. On the basis of the relationship between electronic properties of the substituent and ratios of products, a plausible reaction mechanism is provided. Furthermore, the present reaction could be applied to heterocyclic ketones giving bihetaryl compounds.
- Nishiwaki, Nagatoshi,Yamashita, Keiko,Azuma, Mayumi,Adachi, Tomoko,Tamura, Mina,Ariga, Masahiro
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p. 1996 - 2000
(2007/10/03)
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- Molecular squares, rectangles and infinite helical chains utilising the simple 'corner' ligand 4-(2-pyridyl)-pyrimidine
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The ligand 4-(2-pyridyl)-pyrimidine forms multinuclear Ag(I) complexes by a combination of chelating and bridging coordination modes; molecular shape (square or rectangle) and degree of aggregation depend on the anion used.
- Beauchamp, Derek A.,Loeb, Stephen J.
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p. 2484 - 2485
(2007/10/03)
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- Photochemical ring contraction of 4-heteroaryl-substituted 1,4(or 3,4)-dihydropyrimidines into imidazoles
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Photolysis of 4-R-1,4(or 3,4)-dihydropyrimidines causes ring contraction into imidazoles, provided that the substituent R is capable of sufficiently stabilizing an anionic centre (R=2-thiazolyl, 2-pyridyl, 4-pyridyl).Chemical evidence is presented to show
- Stoel, R. E. van der,Plas, H. C. van der,Jongejan, H.
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p. 364 - 367
(2007/10/02)
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