Search results for "405"
showing 10 items of 3208 documents
A new polyketide from the bark of Hypericum roeperianum Schimp. (Hypericaceae)
2019
The isolation and spectroscopic data of a hitherto undescribed polyketide (1) from Hypericum roeperianum Schimp. (Hypericaceae) together with six known compounds (2–7) is herein reported. The struc...
A metal-free and regioselective approach to (Z)-β-fluorovinyl sulfones and their chemoselective hydrogenation to β-fluoroalkyl sulfones
2018
Abstract A highly regioselective, metal-free hydrofluorination reaction of alkynyl sulfones was developed using TBAF—one of the cheapest and most commonly available fluoride sources. In addition, the reactivity of the resulting β-fluorovinyl sulfones was studied, focusing on their selective hydrogenation reaction. Both β-fluorovinyl sulfones and their hydrogenation products β-fluoroalkyl sulfones may find applications in medicinal and agrochemical sciences.
Unveiling the high reactivity of cyclohexynes in [3 + 2] cycloaddition reactions through the molecular electron density theory
2018
[3 + 2] cycloaddition (32CA) reactions of cyclohexyne, a cyclic strained acetylene, with methyl azide and methoxycarbonyl diazomethane have been studied within the Molecular Electron Density Theory (MEDT) at the MPWB1K/6-311G(d) computational level. These 32CA reactions, which take place through a one-step mechanism involving highly asynchronous transition state structures, proceed with relatively low activation enthalpies of 6.0 and 4.3 kcal mol-1, respectively, both reactions being strongly exothermic. The reactions are initiated by the creation of a pseudoradical center at one of the two acetylenic carbons of cyclohexyne with a very low energy cost, 1.0 kcal mol-1, which promotes the eas…
Influence of Substituent and Benzoannulation on Photophysical Properties of 1-Benzoylmethyleneisoquinoline Difluoroborates
2015
A series of 1-benzoylmethyleneisoquinoline difluoroborates were synthesized, and their photophysical properties were determined. The effect of the substituent and benzoannulation on their properties was investigated to make a comparison with recently published results focused on related quinolines. The photophysical properties of isoquinoline derivatives differ from those of quinolines, and the most pronounced differences are found for the fluorescence quantum yields. Both experimental and theoretical approaches were used to explain the observed photophysical properties.
Cobaltocenium substituents as electron acceptors in photosynthetic model dyads
2017
Abstract Cobaltocenium carboxylic acid hexafluorophosphate has been attached to a zinc(II) meso-tetraphenyl porphyrin chromophore via an amide linkage. Optical and electrochemical studies reveal that the metallocene and the porphyrin interact only negligibly in the ground state of the dyad. Photoinduced charge-shift from the zinc porphyrin to the cobaltocenium substituent to give the zinc porphyrin radical cation and the cobaltocene occurs upon exciting the porphyrin with light. Steady state emission, time-resolved fluorescence and transient absorption pump–probe spectroscopy in addition to density functional theory calculations suggest that the charge shift to the cobaltocenium substituent…
Reversible Covalent and Supramolecular Functionalization of Water-Soluble Gold(I) Complexes.
2017
The ligation of gold(I) metalloamphiphiles with biomolecules is reported, using water-soluble AuI -N-alkynyl substituted maleimide complexes. For this purpose, two different polar ligands were applied: 1) a neutral, dendritic tetraethylene glycol-functionalized phosphane and 2) a charged, sulfonated N-heterocyclic carbene (NHC). The retro Diels-Alder reaction of a furan-protected maleimide gold(I) complex, followed by cycloaddition with a diene-functionalized biotin under mild conditions leads to a novel gold(I) metalloamphiphile. The strong streptavidin-biotin binding affinity in buffered aqueous solution of the resulting biotin alkynyl gold(I) phosphane conjugate remains intact. The cytot…
Ionic Liquid Gels: Supramolecular Reaction Media for the Alcoholysis of Anhydrides.
2019
The search of new enantioselective catalysts, able to promote synthetically useful organic reactions with high levels of asymmetric induction, should be associated with the attention to the suitable reaction medium able to achieve the best efficiency in chemical processes. We have investigated the enantioselective desymmetrization of cyclic meso-anhydrides in nonconventional reaction media such as ionic liquids and supramolecular gels. With this aim, we examined several variables in the reacting system: the nature of ionic liquid used as the reaction medium, the gelation solvent, the structure of the anhydrides, the structure of alcohols, the chiral catalysts, and the reaction conditions, i…
Combining Amines and 3-(2-Pyridyl)-[1,2,3]Triazolo[1,5-a]pyridine: An Easy Access to New Functional Polynitrogenated Ligands
2019
Triazolopyridine-pyridine amine ligands are easily obtained by means of either thermal- or copper(II)-mediated reactions. Starting from a readily accessible iodo derivative of triazolopyridine-pyridine and different amines, this new family of compounds combines aromatic and aliphatic nitrogen atoms with promising coordinating properties. Furthermore, chemical derivatization of a new triazolopyridine-pyridine diamine compound, N1-[6-([1,2,3]triazolo[1,5-a]pyridin-3-yl)pyridin-2-yl]ethan-1,2-diamine, allows the preparation of several remote-pyridine-containing ligands.
First titanium-catalyzed 1,4-hydrophosphination of 1,3-dienes
2010
International audience
Cis versus Trans: The Coordination Environment about the Tin(IV) Atom in Spirocyclic Amino Alcohol Derivatives.
2018
The syntheses of amino alcohols MeN(CH2 CH2 CMe2 OH)2 (1), MeN(CMe2 CH2 OH)(CH2 CMe2 OH) (2), MeN(CH2 CH2 CH2 OH)(CH2 CMe2 OH) (3), MeN(CH2 CH2 CMe2 OH)(CH2 CMe2 OH) (4), MeN(CH2 CH2 CMe2 OH)(CH2 CH2 OH) (5), and MeN(CH2 CH2 OH) (CH2 CH2 CH2 OH) (6) as well as spirocyclic tin(IV) alkoxides spiro-[nBuN(CH2 CMe2 O)2 ]2 Sn (7), spiro-[MeN(CH2 CH2 CMe2 O)2 ]2 Sn (8), spiro-[para-FC6 H4 N (CH2 CMe2 O)2 ]2 Sn (9), spiro-[MeN(CMe2 CH2 O)(CH2 CMe2 O)]2 Sn (10), spiro-[MeN(CH2 CH2 CH2 O)(CH2 CMe2 O)]2 Sn (11), spiro-[MeN(CH2 CH2 CMe2 O)(CH2 CMe2 O)]2 Sn (12), spiro-[MeN(CH2 CH2 CMe2 O)(CH2 CH2 O)]2 Sn (13) and spiro-[MeN(CH2 CH2 O)(CH2 CH2 CH2 O)]2 Sn (14) are reported. The compounds were characteri…