Search results for "chemoselectivity"
showing 10 items of 38 documents
Exploring the Chemoselectivity towards Cysteine Arylation by Cyclometallated Au III Compounds: New Mechanistic Insights
2020
To gain more insight into the factors controlling the efficient cysteine arylation by cyclometalated Au(III) complexes, the reaction between selected gold compounds and different peptides was investigated by high‐resolution liquid chromatography electrospray ionization mass spectrometry (HR‐LC‐ESI‐MS). The deducted mechanisms of C–S cross‐coupling, also supported by density functional theory (DFT) and quantum mechanics/molecular mechanics (QM/MM) calculations, evidenced the key role of secondary peptidic gold binding sites in favouring the process of reductive elimination.
High chemoselectivity of CS dipolarophile in 1,3-dipolar cycloaddition of nitrilimines and 1,2,4-triazepin-5-one derivatives: experimental, theoreti…
2005
Substituted 2,7-dimethyl-3-thioxo-3,4,5,6-tetrahydro-2H-[1,2,4]triazepin-5-one reacts as a dipolarophile with several N-aryl-C-ethoxycarbonylnitrilimines, in equimolar quantities, to give, in all cases, two types of products: diethyl 3-(p-aryl)-2-[N′-(p-aryl)-N′-(2′,7′-dimethyl-5′-oxo-5′,6′-dihydro-2H-[1,2,4]triazepin-3′-yl)-hydrazino]-2,3-dihydro[1,3,4]thiadiazole-2,5-dicarboxylate (3a–3c in 20–25% yield) and ethyl 4-(p-aryl)-5-imino-1,4-dihydro[1,3,4]thiadiazole carboxylate (4a–4c in 45–50% yield). When 1:2 stoichiometry was used, the formation of product 3 (50%) was favoured. The reaction is entirely chemo- and regioselective. The structures of the compounds obtained, where aryl stands f…
Understanding the local reactivity in polar organic reactions through electrophilic and nucleophilic Parr functions
2013
[EN] Building upon our recent studies devoted to the bonding changes in polar reactions [RSC Advances, 2012, 2, 1334 and Org. Biomol. Chem., 2012, 10, 3841], we propose herein two new electrophilic, P-k(+), and nucleophilic, P-k(-), Parr functions based on the spin density distribution at the radical anion and at the radical cation of a neutral molecule. These local functions allow for the characterisation of the most electrophilic and nucleophilic centres of molecules, and for the establishment of the regio- and chemoselectivity in polar reactions. The proposed Parr functions are compared with both, the Parr-Yang Fukui functions [J. Am. Chem. Soc. 1984, 106, 4049] based on frontier molecul…
Cross-Metathesis Reactions as an Efficient Tool in the Synthesis of Fluorinated Cyclic β-Amino Acids
2009
The synthesis of enantiomerically pure, cyclic, gamma,gamma-difluorinated beta-amino acids with various ring sizes has been carried out with a cross-metathesis (CM) reaction being one of the key steps, followed by a Dieckmann-type condensation to bring about the cyclization. Subsequent catalytic hydrogenation under microwave irradiation with (-)-8-phenylmenthol as a chiral auxiliary led to the successful chemo- and diastereoselective chemical reduction of the resulting cyclic beta-enamino esters. The efficiency and scope of the CM reaction with different types of fluorinated imidoyl chlorides and unsaturated esters has also been studied in order to determine the optimal reaction conditions …
New Strategy for the Stereoselective Synthesis of Fluorinated β-Amino Acids
2002
Racemic and chiral nonracemic alpha-substituted and alpha-unsubstituted beta-fluoroalkyl beta-amino acid derivatives 6 and 9 have been synthesized in two steps starting from fluorinated imidoyl chlorides 1 and ester enolates. This approach is based on the chemical reduction of previously obtained gamma-fluorinated beta-enamino esters 4 by using ZnI(2)/NaBH(4) in a nonchelated aprotic medium (dry CH(2)Cl(2)) as the reducing agent. A metal-chelated six-membered model has been suggested to explain the stereochemical outcome of the reduction reaction. The process takes place with high yields and with moderate to good diastereoselectivity. The best results related to diastereoselective reduction…
A convenient synthesis of unsymmetrically substituted terphenyls of biologically active stilbenes via a double Suzuki cross-coupling protocol
2003
A double Suzuki cross-coupling protocol has been devised as a practical route to a variety of terphenyls. Good chemoselectivity was observed. Unsymmetrically substituted triphenylenes were also easily prepared.
A Next‐Generation Air‐Stable Palladium(I) Dimer Enables Olefin Migration and Selective C−C Coupling in Air
2020
Abstract We report a new air‐stable PdI dimer, [Pd(μ‐I)(PCy2 tBu)]2, which triggers E‐selective olefin migration to enamides and styrene derivatives in the presence of multiple functional groups and with complete tolerance of air. The same dimer also triggers extremely rapid C−C coupling (alkylation and arylation) at room temperature in a modular and triply selective fashion of aromatic C−Br, C−OTf/OFs, and C−Cl bonds in poly(pseudo)halogenated arenes, displaying superior activity over previous PdI dimer generations for substrates that bear substituents ortho to C−OTf.
Investigations on isomerization and rearrangement of polycyclic arenes under oxidative conditions – Anodic versus reagent-mediated reactions
2019
Abstract Electro-organic conversions at an active molybdenum anode enable the formation of fused arenes. High chemoselectivity was achieved under anodic conditions, and a reagent-induced selectivity was observed by comparison with results of MoCl5-mediated reactions. Polycyclic arenes like phenanthrenes, triphenylenes, chrysenes, or helicenes were selectively obtained in yields up to 87% and in some cases unusual rearrangements were crucial for the product formation.
Syntheses of (+)-alismoxide and (+)-4-epi-alismoxide.
2006
The first total syntheses of (+)-alismoxide and (+)-4-epi-alismoxide are reported. Formal chemo-, regio-, and stereoselective addition of water to 10alpha-acetoxy-1alphaH,5betaH-guaia-3,6-diene afforded the target compounds after reduction. The absolute stereochemistry of (+)-alismoxide has been established. The low [alpha](D) +8.6 value indicates that significant amounts of alismoxide result from biosynthetic processes. Furthermore, the structure of the natural guaienediol isolated from Silphium perfoliatum has been corrected to (-)-alismoxide.
Chemoselective heterogeneous iridium catalyzed hydrogenation of cinnamalaniline
2020
International audience; Selective hydrogenation of unsaturated imines over heterogeneous catalysts is an ecologically feasible and effective way to produce commercially valuable saturated imines and unsaturated amines under mild conditions, avoiding the utilization of toxic halides. The liquid-phase hydrogenation of a model imine, cinnamalaniline, over Ir, Ru, Pd and Au catalysts was studied in polar protic (methanol, 2-propanol), polar aprotic (methyl tert-butyl ether) and non-polar aprotic (toluene) solvents at 40-80°C under atmospheric hydrogen pressure. Different metal oxides (Al 2 O 3 , ZrO 2 , SiO 2) and carbon composites based on carbon nitrides synthesized by pyrolysis of ethylenedi…