Kinetics and mechanism of organocatalytic aza-Michael additions: direct observation of enamine intermediates.

Kinetics and mechanism of organocatalytic aza-Michael additions: direct observation of enamine intermediateswz

Dihydrooxazine oxides as key intermediates in organocatalytic Michael additions of aldehydes to nitroalkenes.

Pause and play: dihydrooxazine oxides are stable intermediates that are protonated directly, without the intermediacy of the zwitterions, in organocatalytic Michael additions of aldehydes and nitroalkenes (see scheme, R=alkyl). Protonation of these species explains both the role of the acid co-catalyst in these reactions, and the observed stereochemistry when the reaction is conducted with α-al...

A Theoretical Investigation of Kinetics and Mechanism of Aza-Cope Rearrangement

A theoretical study of the kinetic and mechanism of 3-aug-Cope rearrangement in gas phase was performed usingDET methods at B3LYP levels of theory with 6-3114iG(d,p) bass set at 298.I5K. Equilibrium moleculargeometries and harmonic vibrational frequencies of the reactant, transition state Did product were calculated. Then,rate constant and activation thermodynamics parameters were calculated an...

Catalytic enantioselective direct Michael additions of ketones to alkylidene malonates

Enantioselective direct Michael additions of ketones using (S)-1-(2-pyrrolidinylmethyl)-pyrrolidine as a catalyst are described. Michael adducts with up to 91% e.e. were obtained by the reaction of alkylidene malonates with simple unactivated ketones under mild reaction conditions. © 2001 Elsevier Science Ltd. All rights reserved. An increasing demand for optically active compounds has stimulat...

The direct and enantioselective organocatalytic alpha-oxidation of aldehydes.

The first direct enantioselective catalytic alpha-oxidation of carbonyls has been accomplished. The use of enamine catalysis has provided a new organocatalytic strategy for the enantioselective oxyamination of aldehydes, to generate alpha-oxyaldehydes, important chiral synthons for natural product and medicinal agent synthesis. The use of l-proline as the asymmetric catalyst has been found to m...