A Polystyrene‐Supported, Highly Recyclable Squaramide Organocatalyst for the Enantioselective Michael Addition of 1,3‐Dicarbonyl Compounds to β‐Nitrostyrenes

Abstract

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 Michael addition of 1,3-dicarbonyl compounds to b-nitrostyrenes. The PS-supported squaramide could be recycled up to 10 times.

Solid state structural relation and binary melting phase diagram of (S-) and racemic 2-(2-nitro-1-phenylethyl)-1,3-diphenyl-propane-1,3-dione

“…[ 4 , 5 , 6 , 7 , 8 , 9 ]. Most of the major optically active products are assigned as (S)-configuration based on various predictions and on the solved structure of a chloro substituted derivative of (1) [2].…”

Novel Chiral Bifunctional L‐Thiazoline‐Thiourea Derivatives: Design and Application in EnantioselectiveMichael Reactions

“…Over the past few years, bifunctional tertiary amine‐thiourea organocatalysts have emerged as new and efficient organocatalysts for asymmetric reactions . It was found that the cinchona alkaloid family and its derivatives as the chiral amine parts of catalysts possessed high catalytic activity resulting in a high ee value in the asymmetric Michael addition . However, there are only a few examples that chiral thiazoline‐catalysts have been employed since they were first investigated by Helmchen et al in 1991 .…”

Catalytic Enantioselective Flow Processes with Solid‐Supported Chiral Catalysts

“…We postulated that Brønsted acids and H‐bond donors would be ideal candidates for immobilization, given the fact that they do not establish covalent bonds with the substrates, thus reducing the possible pathways for catalyst deactivation . On this basis, we prepared the polystyrene‐supported bifunctional squaramide 18 , that proved highly active and selective in the Michael addition of active carbonyl compounds to nitroalkenes . Even more importantly, it was a very robust material that could be recycled at least ten times.…”