Search results for "SELE"
showing 10 items of 4721 documents
C-H Bond Arylation of Pyrazoles at the β-Position: General Conditions and Computational Elucidation for a High Regioselectivity
2021
International audience; Direct arylation of most five-membered ring heterocycles are generally easily accessible and strongly favored at the α-position using classical palladium-catalysis. Conversely, regioselective functionalization of such heterocycles at the concurrent β-position remains currently very challenging. Herein, we report general conditions for regioselective direct arylation at the β-position of pyrazoles, while C-H α-position is free. By using aryl bromides as the aryl source and a judicious choice of solvent, the arylation reaction of variously N-substituted pyrazoles simply proceeds via β-C-H bond functionalization. The β-regioselectivity is promoted by a ligand-free palla…
Phospholylmethano P-chirogenic-phosphine-borane as P-(η2-BH3)-chelating ligands of rhodium (I): Synthesis, characterization and asymmetric hydrogenat…
2021
International audience; The stereoselective synthesis of new phospholylmethano P-chirogenic-phosphine-borane was achieved by P-C bond formation of the bridge, using electrophilic or nucleophilic P*-building blocks. These P1CH2P2*.BH3 ligands behaved as chelating (κ1-P1)-(η2-BH3) entities towards the cationic rhodium(I) centre. The resulting chiral rhodium complexes were tested in asymmetric rhodium catalyzed hydrogenation of methyl 2-(acetamido)acrylate.
Excited State N−H Tautomer Selectivity in the Singlet Energy Transfer of a Zinc(II)-Porphyrin-Truxene-Corrole Assembly
2017
International audience; An original corrole-containing polyad for S-1 energy transfer, in which one zinc(II)-porphyrin donor is linked to two free-base corrole acceptors by a truxene linker, is reported. This polyad exhibits a rapid zinc(II)-porphyrin*free-base corrole transfer (4.83x10(10)s(-1); 298K), even faster than the tautomerization in the excited state processes taking advantage of the good electronic communication provided by the truxene bridge. Importantly, the energy transfer process shows approximately 3-fold selectivity for one corrole N-H tautomer over the other even at low temperature (77K). This selectivity is due to the difference in the J-integral being effective in both t…
ChemInform Abstract: Boron Aldol Additions with Erythrulose Derivatives: Dependence of Stereoselectivity on the Type of Protecting Group.
2010
Abstract Boron aldol additions of 1- O -silylated 3,4-di- O -benzyl- and 3,4-di- O -benzoyl- l -erythrulose and achiral aldehydes using dicyclohexylboron chloride have been investigated. The dibenzyl derivative gave syn/syn stereoisomers with high stereoselectivity, whereas the dibenzoyl derivative gave syn/anti stereoisomers. It is believed that, while the dibenzoyl erythrulose gives rise to the E enolate in the presence of dicyclohexylboron chloride, as usually observed with this reagent, only the Z enolate is formed in the case of the dibenzyl derivative.
Electrochemical monitoring of the oxidative coupling of alkynes catalyzed by triphenylphosphine gold complexes
2012
Electrochemical monitoring of the oxidative coupling of alkynes in the homogeneous phase through catalytic cycles involving triphenylphosphine gold complexes and selectfluor as oxidant reveals that at least two gold species in +3 and +1 oxidation states are implicated. Electrochemically driven homocoupling of terminal alkynes using molecular oxygen as the oxidant can be performed using such catalysts. Keywords: Gold catalysis, Oxidative coupling of alkynes, Oxygen, Voltammetry
Homoleptic Pnictogen-Chalcogen Coordination Complexes
2012
The synthesis and structural characterization of dicationic selenium and tellurium analogues of the carbodiphosphorane and triphosphenium families of compounds are reported. These complexes, [Ch(dppe)][OTf](2) [Ch = Se, Te; dppe = 1,2-bis(diphenylphosphino)ethane; OTf = trifluoromethanesulfonate], are formed using [Ch](2+) reagents via a ligand-exchange protocol and represent extremely rare examples of homoleptic pnictogen → chalcogen coordination complexes. The corresponding arsenic compounds were also prepared, [Ch(dpAse)][OTf](2) [Ch = Se, Te; dpAse = 1,2-bis(diphenylarsino)ethane], exhibiting the first instance of an arsenic → chalcogen dative bond. The electronic structures of these un…
Synthesis of novel fluorinated building blocks via halofluorination and related reactions.
2020
A study exploring halofluorination and fluoroselenation of some cyclic olefins, such as diesters, imides, and lactams with varied functionalization patterns and different structural architectures is described. The synthetic methodologies were based on electrophilic activation through halonium ions of the ring olefin bonds, followed by nucleophilic fluorination with Deoxo-Fluor®. The fluorine-containing products thus obtained were subjected to elimination reactions, yielding various fluorine-containing small-molecular entities.
Applications and stereoselective syntheses of P-chirogenic phosphorus compounds.
2016
International audience; Phosphorus compounds bearing chirality on the P-center are usually qualified as P-chirogenic or P-stereogenic. This chemical class concerns natural products, agrochemistry, molecular materials, biology and pharmacy, although it is certainly in coordination chemistry and in asymmetric catalysis using chiral transition metal complexes that P-chirogenic phosphorus compounds are the most used. The chiral phosphine ligands and their uses in asymmetric metal-catalyzed reactions have been widely reviewed in literature. However, an overview covering the applications as well as the stereoselective syntheses of all classes of phosphorus compounds has not yet been provided. Thi…
Les enfants difficiles à table : conceptualisation et évolution
2022
L'objectif du présent article est de proposer un état des lieux des études récentes permettant d'offrir un cadre conceptuel et opérationnel au concept de comportement difficile à table, tout en mettant en lumière les conséquences psychologiques pour l'enfant, ainsi que les pratiques éducatives parentales associées. L'article ambitionne aussi de déterminer dans quelle mesure un enfant difficile est un mangeur à risque de développer ultérieurement des troubles du comportement alimentaire (anorexie mentale, ARFID), et quelles seraient les pistes à privilégier, en termes de guidance parentale, pour accompagner l'enfant.
CCDC 1573804: Experimental Crystal Structure Determination
2017
Related Article: Paul J. Ragogna, Cameron Graham, Clement Millet, Amy N Price, Juuso Valijus, Michael J Cowley, Heikki Tuononen|2017|Chem.-Eur.J.|24|672|doi:10.1002/chem.201704337