Quaternary Ammonium-Based Functionalized Polyacrylonitrile Fibers with Polarity Tunable Inner Surface Microenvironment for C–C Bond Forming Reactions under Continuous Flow Conditions

Abstract

A series of quaternary ammonium-based (QAB) functionalized polyacrylonitrile fibers as superbase catalysts for CC bond forming reactions in water were prepared. Alkyl with different chain lengths and benzyl were used to tune the hydrophobicity/hydrophilicity and polarity of the inner surface microenvironment of the QAB functionalized fiber catalysts, and the different microenvironment and the active site synergistically promote the completion of the reaction. The mechanism of the influence of different hydrophilic/hydrophobic catalysts on catalytic activity was proposed. The quaternary ammonium-based functionalized fibers with eight carbon alkyl chains (PANQAB‑8F) as the optimal catalyst performed excellently in green water solvent with specific advantages of low catalyst dosage, mild conditions, high efficiency, and extensive substrate adaptation. Furthermore, the PANQAB‑8F catalyst is very suitable for the continuous flow process, and more than 86% yield was obtained even after the continuous reaction for 160 h; the fiber can be recovered easily and recycled more than 10 times in the continuous-flow system.

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

“…As an example, Tao's group optimised several reactions in batch exploiting a quaternary ammonium functionalised PANF as catalyst (PAN QAB-8 F). They also reported the Henry reaction of 4-chlorobenzaldehyde (64) in flow (Scheme 23) [136]. The catalyst enables the use of water as the solvent; however, in the flow setup, an organic solvent was needed to form a monophasic solution.…”

Cotton Fabric-Supported Cationic Acrylate Polymer as an Efficient and Recyclable Catalyst for Williamson Ether Synthesis Reaction in Solid–Liquid–Liquid Phase Transfer Catalysis System

“… 16 − 25 However, there are few research studies on the immobilization of the phase-transfer catalyst on the fabric. 26 − 28 In the preparation of the reported catalytic fabric, the pretreatment was required and the active group (NH 2 or OH) was introduced on the surface of the fiber. However, the pretreatment induced the high cost and complex preparation process.…”

“…Fabric has been used as a support for the catalyst immobilization because of the cheap cost, being facile, and high specific surface area, such as acrylic fabric and nylon fabric. , These immobilized catalysts with the fabric have exhibited excellent catalytic activity and reusability in the acid, basic, and noble metal catalytic reaction systems. − However, there are few research studies on the immobilization of the phase-transfer catalyst on the fabric. − In the preparation of the reported catalytic fabric, the pretreatment was required and the active group (NH 2 or OH) was introduced on the surface of the fiber. However, the pretreatment induced the high cost and complex preparation process.…”

Tuning Microenvironment of Quaternary Ammonium Salt and Tertiary Amine Bifunctionalized Polyacrylonitrile Fiber for Cooperatively Catalyzed Aza-Michael Addition

“…PANF, widely used in textile industry, has advantages such as low cost, easy availability, high mechanical strength, corrosion resistance and braid-ability [23,24]. It contains sufficient cyano groups that can form carboxyl, amido or other groups through facile reactions [25,26]. In our previous reports, PANF has been used to immobilize quaternary ammonium salt [25], phosphorous acid [27], pyrrolidine [28], tertiary amine [29], L-lysine [30], etc., making functionalized fiber catalysts with high activity, simple preparation and good recyclability [31,32].…”

“…In our previous reports, PANF has been used to immobilize quaternary ammonium salt [25], phosphorous acid [27], pyrrolidine [28], tertiary amine [29], L-lysine [30], etc., making functionalized fiber catalysts with high activity, simple preparation and good recyclability [31,32]. The immobilization process generates middle and deep modification in the surface, so that a special microenvironment surrounding active site is constructed, which helps to improve the catalytic performance [26,33].…”