Directing the Activation of Donor-Acceptor Cyclopropanes Towards Stereoselective 1,3-Dipolar Cycloaddition Reactions by Brønsted Base Catalysis
作者:Jakob Blom、Andreu Vidal-Albalat、Julie Jørgensen、Casper L. Barløse、Kamilla S. Jessen、Marc V. Iversen、Karl Anker Jørgensen
DOI:10.1002/anie.201706150
日期:2017.9.18
first stereoselective organocatalyzed [3+2] cycloaddition reaction of donor-acceptor cyclopropanes is presented. By using an optically active bifunctional Brønsted base catalyst, racemic di-cyano cyclopropylketones can be activated to undergo a stereoselective 1,3-dipolar reaction with mono- and polysubstituted nitroolefins. The reaction affords functionalized cyclopentanes with threecontiguous stereocenters
Structural optimization of thiourea-based bifunctional organocatalysts for the highly enantioselective dynamic kinetic resolution of azlactones
作者:Albrecht Berkessel、Santanu Mukherjee、Thomas N. Müller、Felix Cleemann、Katrin Roland、Marc Brandenburg、Jörg-M. Neudörfl、Johann Lex
DOI:10.1039/b607574f
日期:——
describes the synthesis of a library of structurally diverse bifunctionalorganocatalysts bearing both a quasi-Lewis acidic (thio)urea moiety and a Bronsted basic tertiary amine group. Sequential modification of the modular catalyst structure and subsequent screening of the compounds in the alcoholytic dynamickineticresolution (DKR) of azlactones revealed valuable structure-activity relationships. In particular