Membrane-Grafted Asymmetric Organocatalyst for an Integrated Synthesis–Separation Platform

Abstract

In this work we introduce a sustainable membrane-based synthesis–separation platform for enantioselective organocatalysis. An azido derivatized cinchona-squaramide bifunctional catalyst was synthesized and subsequently grafted to the surface of a polybenzimidazole-based nanofiltration membrane. The favorable effect of the covalent graftingdue to the change in geometry and increased secondary interactionson the catalytic activity due to conformational changes was confirmed by quantum chemical calculations. Asymmetric Michael and aza-Michael reactions of 1,3-dicarbonyl and indole, pyrazole, and triazole derivatives to β-nitrostyrene were performed with as high as 99% enantiomeric excess. This report on the enantioselective aza-Michael reaction of pyrazoles and triazoles opens new frontiers in the application of squaramide-based cinchona catalysts. A catalytic membrane cascade reactor was developed for an integrated synthesis–purification process allowing at least 98% product and substrate recovery, and quantitative in situ solvent recycling. The sustainability of the synthetic methodology was assessed through E-factor and carbon footprint.

Isolation of Nb2Se9 Molecular Chain from Bulk One-Dimensional Crystal by Liquid Exfoliation

“…Since the organic solvents used in the solution process mainly have toxicity problems and sustainability issues, it is necessary to increase the process efficiency to minimize the use of solvents and to select less hazardous solvents [41,42]. In order to find the best exfoliation solvent for Nb 2 Se 9 crystals, 16 common solvents with different dielectric constants and surface energies were studied (Table 1).…”

Modification Effects of B2O3 on The Structure and Catalytic Activity of WO3-UiO-66 Catalyst

“…Notably, there is no distinction between the XRD and FTIR results before and after the reaction, and ICP experiment proved that almost no B and W were detected in the reaction solution, indicating that 15 wt % B 2 O 3 -40 wt % WO 3 /UiO-66 catalyst shows high stability and catalytic activity for the selective oxidation of CPE to GA. We believe that the decrease in the observed catalytic activity is possibly because of the loss of small amounts of catalyst in the process of filtration and washing. Recently, Szekely et al reported that the covalent grafting of an organocatalyst to a membrane surface would allow for the development of a new, sustainable methodology consisting of catalysis, product purification, excess reagent, and solvent recovery in a single unit operation, in addition to overcoming the lost of catalysts [62]. Pourjavadi el al.…”

Scalable Enantiomeric Separation of Dialkyl‐Arylphosphine Oxides Based on Host–Guest Complexation with TADDOL‐Derivatives, and their Recovery

“…OSN is a sustainable, pressure‐driven membrane‐based technology that is capable of distinguishing compounds between 50 and 2000 g mol –1 in organic media . OSN processes developed for chiral molecules include enantioseparation, asymmetric membrane reactor, and continuous asymmetric catalyst recycling …”

“…OSN is a sustainable, pressure-driven membrane-based technology that is capable of distinguishing compounds between 50 and 2000 g mol -1 in organic media. [18] OSN processes developed for chiral molecules include enantioseparation, [19] asymmetric membrane reactor, [20] and continuous asymmetric catalyst recycling. [21] In our earlier study, one optically active diaryl-alkylphosphine oxide was prepared, and those results suggested that TADDOL derivatives may be generally applicable resolving agents for acyclic phosphine oxides.…”