Chiral Bifunctional Thioureas and Squaramides Grafted into Old Polymers of Intrinsic Microporosity for Novel Applications.

María Valle,Laura Martín,Rafael Pedrosa,José M Andrés,Alicia Maestro

doi:10.3390/polym11010013

María Valle, Laura Martín + Show 3 more

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https://doi.org/10.3390/polym11010013

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Journal: Polymers	Publication Date: Dec 21, 2018
Citations: 11	License type: CC BY 4.0

Affiliation: University of Valladolid

Abstract

We have prepared different polymeric chiral bifunctional thioureas and squaramides by modification of the very well-known polymers of intrinsic microporosity (PIM), specifically PIM-1 and PIM-CO-1, to be used as recoverable organocatalysts. The installation of the chiral structures into the polymers has been done in two or three steps in high yields. The catalytic activity of the resulting materials has been proved in the stereoselective nitro-Michael addition and in a cascade process, which allows the synthesis of enantioenriched 4H-chromene derivatives. Squaramide II and thiourea III have been used in six cycles maintaining their activity.

Highlights

Since the discovery of polymers of intrinsic microporosity (PIMs) fifteen years ago [1], a great deal of work has been developed around their applications in physicochemical processes [2,3,4]
This group has been converted into carboxylic acids [22,23], thioamides [24], amidoximes [25], tetrazoles [26,27], and amides [28] and has been reduced to diamines [29], but all these transformations have been directed to the synthesis of modified PIM-1 to get improvement in gas permeation and in diffusion processes
It is clear that all the CN groups in starting PIM-1 have been reduced to amine groups because the absorption at

Summary

Introduction

Since the discovery of polymers of intrinsic microporosity (PIMs) fifteen years ago [1], a great deal of work has been developed around their applications in physicochemical processes [2,3,4]. Only the archetypal PIM-1 [12] has been subjected to additional modifications based on the transformation of the nitrile groups. This group has been converted into carboxylic acids [22,23], thioamides [24], amidoximes [25], tetrazoles [26,27], and amides [28] and has been reduced to diamines [29], but all these transformations have been directed to the synthesis of modified PIM-1 to get improvement in gas permeation and in diffusion processes. Some other types of polymers, such as chiral helical polymers [30] or copolymers [31] with different pendant substituents [32] have been successfully used as catalysts in enantioselective Rauhut-Currier [33] or aldol [34] reactions

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