Title
Chiral Anion Triggered Helical Poly(ionic liquids)
Author
Pothanagandhi N, Sivaramakrishna Akella, Vijayakrishna Kari
Year
2016
Journal
Polymer Chemistry
Abstract
Synthetic chiral polymers and helical polymers are finding increasing applications in catalysis and chiral recognition. Herein we have induced the chirality in the PILs at the anionic site by introducing optically pure amino acids by simple anionic exchange reaction. RAFT derived imidazolium-based poly(ionic liquids) [poly(ViEIm) Br] and the commercially available poly(diallyldimethylammonium chloride) were utilized for the synthesis of six different chiral PILs (poly(ViEIm)-Lpr, poly(ViEIm)-D-pr, poly(ViEIm)-L-his, poly(ViEIm)-D-his, poly(dadma)-L-pr and poly(dadma)-D-pr). The synthesized chiral poly(ionic liquids) (CPILs) were well characterized by NMR, DSC, TGA, specific rotation, CD, SEM and TEM analysis. Chiroptical studies suggested that, introduction of chiral anions at the anionic site of achiral PIL-Br/OH will trigger the helicity. These CPILs pocess tuneable chirality as a function of anion. The Chiral PILs possessing L- and D- amino acids as counter anions showed completely opposite helical loops in CD studies and opposite specific rotation values. The morphological studies done by SEM and TEM clearly showed the existence of random double helix nature for some of the synthesized chiral PILs. The synthesized CPILs were further used as catalysts for Baylis Hillman reaction between methyl vinyl ketone and aryl aldehydes that gave B-H product up to 90% with moderate enantiomeric excess.
Instrument
J-715
Keywords
Circular dichroism, Polymers, Stereochemistry