Enantioselective Thiourea-Catalyzed Additions to Oxocarbenium Ions
作者:Sarah E. Reisman、Abigail G. Doyle、Eric N. Jacobsen
DOI:10.1021/ja801514m
日期:2008.6.1
Asymmetric, catalytic reactions of oxocarbeniumions are reported. Simple, chiral urea and thiourea derivatives are shown to catalyze the enantioselective substitution of silyl ketene acetals onto 1-chloroisochromans. A mechanism involving anion binding by the chiral catalyst to generate a reactive oxocarbeniumion is invoked. Catalysts bearing tertiary benzylic amide groups afforded highest enantioselectivities
Stereodivergent Anion Binding Catalysis with Molecular Motors
作者:Ruth Dorel、Ben L. Feringa
DOI:10.1002/anie.201913054
日期:2020.1.7
A photoresponsive chiral catalyst based on an oligotriazole-functionalized unidirectional molecular motor has been developed for stereodivergent anion binding catalysis. The motor function controls the helical chirality of supramolecular assemblies with chloride anions, which by means of chiralitytransfer enables the enantioselective addition of a silyl ketene acetal nucleophile to oxocarbenium cations
Conformational Control of Chiral Amido-Thiourea Catalysts Enables Improved Activity and Enantioselectivity
作者:Dan Lehnherr、David D. Ford、Andrew J. Bendelsmith、C. Rose Kennedy、Eric N. Jacobsen
DOI:10.1021/acs.orglett.6b01435
日期:2016.7.1
While aryl pyrrolidinoamido-thioureas derived from alpha-amino acids are effective catalysts in a number of asymmetric transformations, they exist as mixtures of slowly interconverting amide rotamers. Herein, the compromising role of amide bond isomerism is analyzed experimentally and computationally. A modified catalyst structure that exists almost exclusively as a single amide rotamer is introduced. This modification is shown to result in improved reactivity and enantioselectivity by minimizing competing reaction pathways.