86607-65-0Relevant articles and documents
The effects of cationic and zwitterionic micelles on the keto-enol interconversion of 2-phenylacetylfuran and 2-phenylacetylthiophene
De Maria, Paolo,Fontana, Antonella,Gasbarri, Carla,Siani, Gabriella
, p. 7176 - 7183 (2005)
The presence of micelles from cationic and zwitterionic surfactants increases the apparent acidity of either the keto and the enol forms of 2-phenylacetylfuran (2PAF) and 2-phenylacetylthiophene (2PAT). This effect can be attributed to the affinity of the surfactant micelles for the enolate of the two substrates. Although the equilibrium constants for keto-enol tautomerism of 2PAF and 2PAT, KT=[enol]/[ketone]=pKaKH-pK aEH, do not change much, the presence of micelles provides an efficient method for producing appreciable quantities of the enolates under mild experimental conditions and in aqueous solutions. The obtained rate-profiles for the ketonisation reactions and the consistency of the kinetic rate constants over a wide range of 'pH' in several overlapping buffers indicate that the pH of the aqueous pseudophase (but not that at the micellar surface) can be controlled by buffers. Moreover, the increase of the acidity and the decrease of the 'water' rate of ketonisation of the enols of 2PAF and 2PAT upon addition of surfactants allow the uncovery of a metal ion catalysed pathway that cannot be observed in absence of surfactants.
Combined Theoretical and Experimental Studies Unravel Multiple Pathways to Convergent Asymmetric Hydrogenation of Enamides
Yang, Jianping,Massaro, Luca,Krajangsri, Suppachai,Singh, Thishana,Su, Hao,Silvi, Emanuele,Ponra, Sudipta,Eriksson, Lars,Ahlquist, M?rten S. G.,Andersson, Pher G.
supporting information, p. 21594 - 21603 (2021/12/27)
We present a highly efficient convergent asymmetric hydrogenation of E/Z mixtures of enamides catalyzed by N,P-iridium complexes supported by mechanistic studies. It was found that reduction of the olefinic isomers (E and Z geometries) produces chiral amides with the same absolute configuration (enantioconvergent hydrogenation). This allowed the hydrogenation of a wide range of E/Z mixtures of trisubstituted enamides with excellent enantioselectivity (up to 99% ee). A detailed mechanistic study using deuterium labeling and kinetic experiments revealed two different pathways for the observed enantioconvergence. For α-aryl enamides, fast isomerization of the double bond takes place, and the overall process results in kinetic resolution of the two isomers. For α-alkyl enamides, no double bond isomerization is detected, and competition experiments suggested that substrate chelation is responsible for the enantioconvergent stereochemical outcome. DFT calculations were performed to predict the correct absolute configuration of the products and strengthen the proposed mechanism of the iridium-catalyzed isomerization pathway.
Iridium-Catalyzed Asymmetric Hydrogenation of N-Alkyl α-Aryl Furan-Containing Imines: an Efficient Route to Unnatural N-Alkyl Arylalanines and Related Derivatives
Mazuela, Javier,Antonsson, Thomas,Knerr, Laurent,Marsden, Stephen P.,Munday, Rachel H.,Johansson, Magnus J.
supporting information, p. 578 - 584 (2018/12/11)
High throughput experimentation (HTE) has enabled the rapid identification of ligand/precatalyst combinations that facilitate highly enantioselective hydrogenations of prochiral N-alkyl α-aryl ketimines containing a furyl moiety. The chiral amines obtained have proven to be modular precursors in the synthesis of unnatural mono N-alkylated arylalanines and related derivatives. (Figure presented.).
