Synthesis of a Novel Magnetic Reusable Organocatalyst Based on 4-Dialkylaminopyridines for Acyl Transformations

Bio-inspired surface modification of iron oxide nanoparticles for active stabilization in hydrogels

Biological materials employ a variety of dynamic interactions in sophisticated composite structures to function adaptively on different time and length scales. Inspired by such designs we develop a novel surface modification approach to promote dynamic interactions between nanoparticles and polymer chains in physical and double network hydrogels. Physical hydrogels are formed via reversible complexation of borate ions with poly(vinyl alcohol) (PVA) and chemical crosslinks are introduced by electron beam irradiation. Dopamine is used for surface modification of magnetic iron oxide nanoparticles (MNPs) in two different ways: the direct treatment results in anchoring via catechol groups, whereas the indirect method leaves the catechol group on the free surface of MNPs. Although the former particles show very good colloidal stability, they lower the network connectivity, which results in lower plateau modulus, faster terminal relaxation, and lower yield stress, presumably due to imposing an extra distance between PVA chains. In contrast to this passive design, the latter particles actively reinforce the network by forming clusters of physical bonds between catechol groups of the individual particles and the monodiol complexes of the borate ions and PVA chains. Moreover, the additional complexes formed upon the introduction of nanoparticles with active surfaces provide further energy dissipation potential and therefore enhance the toughness. This approach can help develop novel hydrogels with superior toughness and multiple stimuli-responsiveness.

Site-selective phenol acylation mediated by thioacids via visible light photoredox catalysis

Site-selective phenol acylation mediated by thioacids via photoredox catalysis is described. This protocol provided facile access to an array of phenolic esters with exclusive acylation priority of phenol hydroxyl group to alcoholic one. Its utility was also demonstrated by the modification of biologically meaningful natural product.

Multicomponent synthesis of new curcumin-based pyrano[2,3-d]pyrimidine derivatives using a nano-magnetic solid acid catalyst

An novel nano-magnetic solid acid catalyst was used for the efficient synthesis of new curcumin-based pyrano[2,3-d]pyrimidine derivatives via a multicomponent reaction under mild conditions.

4-Dialkylaminopyridine modified magnetic nanoparticles: as an efficient nano-organocatalyst for one-pot synthesis of 2-amino-4H-chromene-3-carbonitrile derivatives in water

A new DMAP-based magnetic nano-organocatalyst was developed for efficient one-pot synthesis of 2-amino-4H-chromene-3-carbonitrile derivatives in water as a green solvent.