Search results for "DISCOVERY"

Host—Guest Interactions Involving Cyclodextrins: Useful Complementary Insights Achieved by Polarimetry.

2007

Abstract By means of simple polarimetry, we studied the binding abilities of native α-, β-, and γ-cyclodextrins toward a group of suitably chosen model guests. We were able to get reliable estimations of the binding constants K, spread over a wide range (from 3.7 to 12,300 M−1), allowing us to carry on interesting comparisons. A comprehensive discussion of polarimetric data, and in particular a detailed analysis of the variations ΔΘ of molar optical activities consequent to inclusion, offered us the opportunity to get useful insights into the structure and dynamic behavior of host–guest complexes.

Bildungsmechanismus und eigenschaften von Phenyläthinyl-triphenylphosphoniumbromid

1964

Die reaktion des 2-cyanoisopropylhydroperoxides mit alkali

1966

Indirect regioselective heteroarylation of indoles through a Friedel–Crafts reaction with (E)-1,4-diaryl-2-buten-1,4-diones

2009

Abstract A two-step synthesis of 3-heteroaryl indoles has been developed. The first step of the sequence involves a Friedel–Crafts alkylation of indoles with 1,4-diaryl-2-buten-1,4-diones to give the corresponding indoles bearing a 1,4-dicarbonyl moiety. The reaction is catalyzed by InCl 3 and takes place with good yields. Cyclization of the diones under different Paal–Knorr conditions allows to prepare indoles substituted at the C3 position with 3-furanyl, 3-pyrrolyl- and 3-thienyl moieties.

Die absolute Konfiguration des rechtsdrehenden methyl-n-propyl-phenyl-benzyl-phosphoniumbromids

1965

A density functional theory study for the Diels–Alder reaction between N-acyl-1-aza-1,3-butadienes and vinylamines. Lewis acid catalyst and solvent e…

2002

Abstract The molecular mechanism for the Diels–Alder reaction of N-acyl-1-aza-1,3-butadiene with dimethylvinylamine has been studied using density functional theory methods. This cycloaddition is the nucleophilic attack of the vinylamine to the conjugate position of the unsaturated acyl imine with concomitant ring-closure. The presence of a Lewis acid catalyst coordinated to the acyl oxygen atom decreases markedly the activation energy associated to the nucleophilic attack. This results from an increasing of the electrophilicity of the 1-aza-1,3-butadiene that shift the mechanism from a highly asynchronous concerted process to a polar stepwise one.

A DFT study of the mechanism of Brønsted acid catalysed Povarov reactions

2015

Abstract The molecular mechanism of the Bronsted acid (BA) catalysed Povarov reaction of N -phenyl- C -methoxycarbonyl imine with a methylenecyclopropane (MCP) has been investigated using DFT methods at the MPWB1K/6-31G(d) level. This BA catalysed Povarov reaction is a domino process initialised by the formation of a cationic intermediate which experiences a quick intramolecular Friedel–Crafts reaction yielding the final tetrahydroquinoline. Protonation of the imine nitrogen atom notably increases the electrophilicity of the corresponding species, accelerating the reaction through ionic processes. Analysis of the Parr functions in the initial nucleophilic attack of MCP to the protonated imi…

Crystalline self-assembly induced by aromatic edge-to-face interactions: the crystal structure of 2,6,6,10-tetrabenzyl-2,10-diaza-6-azonia[11]paracyc…

2002

The crystal structure of 2,6,6,10-tetrabenzyl-2,10-diaza-6-azonia[11]paracyclophane bromide reveals several intermolecular aromatic edge-to-face interactions which are important in the three-dimensional growing of the crystalline structure. Molecular dynamics and semiempirical studies indicate that the conformer found in the crystal is not the most stable in solution confirming the important role that edge-to-face interactions play in the structural arrangement found in the solid state.

Synthesis and in vitro evaluation of galanthamine derivatives for examination of nicotinic acetylcholine receptor system

2001

ISunmrary: The syntheses and radioactive labeling of several galanthamine derivatives, 6-O-demethyl-6-O-fluoroethylgalanthamine, 10-N-demethyl-lO-Nfluoroethylgalanthamine and N-methylgalanthaminium are reported. First ill vitro evaluations were carried out to determine their properties as allosterically potentiating ligands of nicotinic receptors. N-methylgalanthaminium was found to be a promising candidate for further investigations. The most commonly applied therapeutic approach to balance nicotinic cholinergic deficits in Alzheimer’s disease (AD) patients is the administration of acetylcholinesterase inhibitors (AChE-I) although they have been proven to be of limited therapeutic value [ …

Fluorinated heterocyclic compounds. A photochemical synthesis of 3-amino-5-perfluoroaryl-1,2,4-oxadiazoles

2001

Abstract A photochemical methodology for the synthesis of 3-amino- (or 3- N -substituted amino) 5-pentafluorophenyl-1,2,4-oxadiazoles is reported. Irradiation of 3-pentafluorobenzoylamino-4-methyl-1,2,5-oxadiazole (Furazan) at 254 nm in methanol and in the presence of ammonia, primary or secondary aliphatic amines produces 3-amino-, 3-( N -alkylamino)-, 3-( N , N -dialkylamino)-5-pentafluorophenyl-1,2,4-oxadiazoles. The photoreaction follows the fragmentation pattern of the furazan ring with the extrusion of acetonitrile and the formation of a counterpart fragment which the nitrogen nucleophile will capture. Depending on the nature of the reagent, displacement of a fluoride anion at the C(5…