Reusable Glucose-Based Crown Ethers Anchored to PVC

Abstract

The recovery and reuse of the enantioselective catalysts produced by tedious work are important not only from the perspective of green chemistry, but also from the point of view of productivity. Some of the carbohydrate-based crown ethers prepared in our research group were able to generate significant asymmetric induction in certain cases. However, they were not recoverable after the synthesis. Therefore, we modified the most effective structure with a propargyl group so that it can be attached to a polymer with an azide–alkyne reaction. It was investigated whether the position of the bonding affects the activity of the crown ethers, hence, the propargyl group was introduced either to the side chain, to the anomeric center or to the benzylidene protecting group. To anchor the macrocycles, low molecular weight PVC was modified with azide groups in 4% and 10%, respectively. It was found that glucose-based crown ether bearing the propargyl group on the benzylidene unit and grafted to PVC in 4% has the highest activity regarding the enantioselectivity (77% ee). The catalyst was recoverable in the Michael addition of diethyl acetamidomalonate to nitrostyrene and it could be reused five times without the loss of enantioselectivity.

Synthetic Modifications of a Pb2+-Sensor Acridono-Crown Ether for Covalent Attachment and Their Effects on Selectivity

“…However, current sustainability requirements encourage chemists to regenerate these host molecules, even if they are easily obtainable. In practice, this requires the covalent immobilization of the host molecules on various solid carriers, such as a stationary phase [ 7 , 8 ], a nanoparticle [ 9 ], a resin [ 10 ], a polymer [ 11 ], etc. Also, the chemical incorporation of the host molecules into solid carriers prevents the contamination of the samples with ionophores during analysis.…”