A Polystyrene-Supported, Highly Recyclable Squaramide Organocatalyst for the Enantioselective Michael Addition of 1,3-Dicarbonyl Compounds to β-Nitrostyrenes
作者:Pinar Kasaplar、Paola Riente、Caroline Hartmann、Miquel A. Pericàs
DOI:10.1002/adsc.201200526
日期:2012.11.12
A chiral squaramide has been supported onto a polystyrene (PS) resin through a copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction and used as a very active, easily recoverable and highly reusable organocatalyst for the asymmetric Michaeladdition of 1,3-dicarbonylcompounds to β-nitrostyrenes. The PS-supported squaramide could be recycled up to 10 times.
Molecular Engineering of β‐Substituted Oxoporphyrinogens for Hydrogen‐Bond Donor Catalysis
作者:Mandeep K. Chahal、Daniel T. Payne、Yoshitaka Matsushita、Jan Labuta、Katsuhiko Ariga、Jonathan P. Hill
DOI:10.1002/ejoc.201901706
日期:2020.1.9
Beta functionalization of oxoporphyrinogens as H‐bonddonor catalysts with binding site designed for dual activation of substrates is reported. Introduction of the β‐substituents enables the catalysis of 1,4‐conjugate additions, sulfa‐Michael additions and Henry/aza‐Henry reactions at low catalyst loadings (≤ 1 mol‐%) under mild conditions.
motifs in organocatalysis, whereas efficient 1,3‐diamine‐derived organocatalysts are very rare. Herein we report a highly efficient camphor‐1,3‐diamine‐derived squaramideorganocatalyst. Its catalytic activity in Michaeladditions of 1,3‐dicarbonyl nucleophiles to trans‐β‐nitrostyrene derivatives provides excellent enantioselectivities (up to >99% ee).
Michaeladditions of different aldehydes and ketones to β-nitrostyrene and 2-(β-nitrovinyl)thiophene in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6) were studied. β-Nitrostyrene was a better acceptor than 2-(β-nitrovinyl)thiophene, in terms of both reactivity and selectivity. Aldehydes proved to be better donors than ketones, which were themselves better than β-diketones. L-proline proved
Bifunctional organocatalysis with squaramide-containing Dawson organo-polyoxotungstates
作者:David Lachkar、Emmanuel Lacôte
DOI:10.1016/j.crci.2015.05.006
日期:2016.1
Résumés Anglais Français Two squaramide-containing organo-polyoxometalates (POMs) have been prepared, which efficiently catalyze the addition of dicarbonyl derivatives onto nitroolefins. The POM surface enhances the reactivity of the squaramide, and the hybrid acts as a bifunctional catalyst, where the highly charged POM surface in the organic medium is a base, which deprotonates the nucleophile and the squaramide activates the nitroalkenes via H-bonds. This opens new perspectives to POM-based catalysis. Supplementary Materials: Supplementary material for this article is supplied as a separate file: mmc1.pdf Deux organo-polyoxométallates (POMs) contenant une fonction squaramide ont été préparés. Ils catalysent l'addition de composés dicarbonylés sur des nitro-oléfines. La surface du POM augmente la réactivité du squaramide. L'hybride agit ainsi comme un catalyseur bifonctionnel, pour lequel un oxo de la surface du POM agit en tant que base en milieu organique et déprotone le nucléophile. Le squaramide active la nitro-oléfine au moyen de liaisons hydrogène. Ce travail ouvre de nouvelles perspectives en catalyse par les POMs. Compléments : Des compléments sont fournis pour cet article dans le fichier séparé : mmc1.pdf