Search results for "Chemoselectivity"
showing 8 items of 38 documents
Understanding the regio- and chemoselective polar [3+2] cycloaddition of the Padwa carbonyl ylides with α-methylene ketones. A DFT study
2009
The regio- and chemoselective polar [3+2] cycloaddition (32CA) of the Padwa carbonyl ylide (CY) with α-methylene ketone (αMK) to yield the oxa-bridged spirocycloadduct has been studied using the DFT method at the B3LYP/6-31G(d) computational level. Six reactive channels associated to the stereo-, regio-, and chemoselective approach modes of the CY to the CC and CO reactive sites of the αMK have been analyzed. DFT calculations for this cycloaddition are in complete agreement with the experimental outcome, explaining the reactivity and selectivity of the formation of the [3+2] cycloadduct. Analysis of the global and local electrophilicity and nucleophilicity indices allows an explanation abou…
Chemodiscrimination of Olefin Bonds Through Cross‐Metathesis Reactions – Synthesis of Functionalized β‐Lactam and β‐Amino Acid Derivatives
2019
Oxidation of Sulfides with a Silica-Supported Peracid in Supercritical Carbon Dioxide under Flow Conditions: Tuning Chemoselectivity with Pressure
2010
Supercritical carbon dioxide is a convenient medium for performing the selective oxidation of sulfides 1 to either sulfoxides 2 or sulfones 3 with [2-percarboxyethyl]-functionalized silica (4) under flow conditions. The chemoselectivity of the reaction, which results from the different diffusion rates of sulfide and sulfoxide over the reagent bed, can be controlled by adjusting the pressure and the hydration of the silica surface as both the solvating power of the mobile phase and the surface activity of the stationary phase determine the migration rates of sulfide 1 and sulfoxide 2 over the supported peroxide. The results elucidate the impact of surface phenomena on the course of chemical …
Polar [3 + 2] cycloaddition of ketones with electrophilically activated carbonyl ylides. Synthesis of spirocyclic dioxolane indolinones
2008
International audience; The [3 + 2] cycloaddition reaction between carbonyl ylides generated from epoxides and ketones (ethyl pyruvate, ethyl phenylglyoxylate, isatin, N-methylisatin and 5-chloroisatin) to give substituted dioxolanes and spirocyclic dioxolane indolinones was investigated. The effect of microwave irradiation on the outcome of the reaction was studied. The thermal reaction between 2,2-dicyano-3-phenyloxirane and N-methylisatin was theoretically studied using DFT methods. This reaction is a domino process that comprises two steps. The first is the thermal ring opening of the epoxide to yield a carbonyl ylide intermediate, whereas the second step is a polar [3 + 2] cycloadditio…
Novel strategy for the synthesis of fluorinated β-amino acid derivatives from Δ2-oxazolines
2001
Abstract Racemic and chiral non-racemic β-fluoroalkyl-β-amino acid derivatives have been prepared in two steps starting from 2-alkyl-Δ2-oxazolines and fluorinated imidoyl chlorides. Subsequent chemoselective reduction of the C-masked β-enamino acid derivatives initially formed provided the target β-amino acids. The process takes place with total chemoselectivity, high yields and satisfactory diastereoselectivity.
ChemInform Abstract: Novel Strategy for the Synthesis of Fluorinated β-Amino Acid Derivatives from Δ2-Oxazolines.
2010
Abstract Racemic and chiral non-racemic β-fluoroalkyl-β-amino acid derivatives have been prepared in two steps starting from 2-alkyl-Δ2-oxazolines and fluorinated imidoyl chlorides. Subsequent chemoselective reduction of the C-masked β-enamino acid derivatives initially formed provided the target β-amino acids. The process takes place with total chemoselectivity, high yields and satisfactory diastereoselectivity.
Synthesis of 1,3-Oxazolidines and 1,3-Dioxolanes by Reaction of (2R, 3R)-3-Methylamino-3-phenyl-1,2-propanediol with Electrophiles
2003
Abstract The chemoselective reaction of (2R, 3R)-3-methylamino-3-phenyl-1,2-propanediol 1 with dimethoxypropane and dichloromethane under different conditions are reported as useful preparative procedures, for the synthesis 1,3-oxazolidines and 1,3-dioxolanes.
Fluorination of some highly functionalized cycloalkanes: chemoselectivity and substrate dependence.
2017
A study exploring the chemical behavior of some dihydroxylated β-amino ester stereo- and regioisomers, derived from unsaturated cyclic β-amino acids is described. The nucleophilic fluorinations involving hydroxy–fluorine exchange of some highly functionalized alicyclic diol derivatives have been carried out in view of selective fluorination, investigating substrate dependence, neighboring group assistance and chemodifferentiation.