%0 Journal Article
%T Membrane-Grafted Asymmetric Organocatalyst for an Integrated Synthesis¨CSeparation Platform
%J -
%D 2018
%R https://doi.org/10.1021/acscatal.8b01706
%X High Resolution Image Download MS PowerPoint Slide In this work we introduce a sustainable membrane-based synthesis¨Cseparation 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¡ªdue to the change in geometry and increased secondary interactions¡ªon 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 ¦Â-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¨Cpurification 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
%U https://pubs.acs.org/doi/10.1021/acscatal.8b01706