Enantioselective β-Protonation by a Cooperative Catalysis Strategy
摘要:
An enantioselective N-hetetoeyclic carbene (NHC)-catalyzed beta-protonation through the orchestration of three distinct organocatalysts has been developed. This cooperative catalyst system enhances both yield and selectivity, compared to only the NHC-catalyzed process. This new method allows for the,efficient conversion of a large scope of aryl-oxobutenoates to highly enantioenriched succinate derivatives and demonstrates the benefits of combining different activation modes in organocatalysis.
Catalytic, Enantioselective β-Protonation through a Cooperative Activation Strategy
作者:Michael H. Wang、David Barsoum、C. Benjamin Schwamb、Daniel T. Cohen、Brian C. Goess、Matthias Riedrich、Audrey Chan、Brooks E. Maki、Rama K. Mishra、Karl A. Scheidt
DOI:10.1021/acs.joc.7b00334
日期:2017.5.5
only feasible, but also adaptable to a kinetic resolution of secondaryalcohols through NHC-catalyzed acylation. In-depth analysis of this process determined that careful catalyst and solvent pairing is critical for optimal yield and selectivity; proper choice of nonpolar solvent provided improved yield through suppression of an oxidative side reaction, while employment of a cooperative catalytic approach
Highly specific fragmentation processes of isomeric mixed esters of phenylsuccinic acid under electron impact
作者:I. Vidavsky、A. Mandelbaum、T. Tamiri、S. Zitrin
DOI:10.1002/oms.1210260420
日期:1991.4
AbstractIsomeric mixed dialkyl phenylsuccinates, PhCH(COOR)CH2COOR′, undergo a highly specific elimination of ROH under electron impact. A deuterium‐labelling study showed that the hydrogen atom from the benzylic position 2 is abstracted in this process. These results suggest the occurrence of a ‘hidden’ hydrogen migration of the benzylic hydrogen atom to the carbonylic oxygen of the remote ester group, followed by the elimination of ROH from the adjacent ester group with the involvement of that hydrogen. Alkoxyl group migrations resulting in the formation of [PhCHOR]+ and [PhCHOR′]+ ions are less specific, although the migration of the remote R′O˙ is significantly preferred in all the pairs of isomers examined. Mechanisms are suggested for the formation of the two ions.
Enantioselective β-Protonation by a Cooperative Catalysis Strategy
作者:Michael H. Wang、Daniel T. Cohen、C. Benjamin Schwamb、Rama K. Mishra、Karl A. Scheidt
DOI:10.1021/jacs.5b02887
日期:2015.5.13
An enantioselective N-hetetoeyclic carbene (NHC)-catalyzed beta-protonation through the orchestration of three distinct organocatalysts has been developed. This cooperative catalyst system enhances both yield and selectivity, compared to only the NHC-catalyzed process. This new method allows for the,efficient conversion of a large scope of aryl-oxobutenoates to highly enantioenriched succinate derivatives and demonstrates the benefits of combining different activation modes in organocatalysis.