The development of nonorthogonal tandem catalysis enables the use of a combination of arbitrary catalysts to rapidly synthesize complex products in a sustainable, efficient, and timely manner.

Trifluoroacetic acid-modulated UiO-66 metal–organic frameworks (MOFs) are used to catalyze the reaction of unprotected aldose sugars with acetylacetone to polyhydroxyalkyl and C-glycosyl furans, known as the Garcia Gonzalez reaction. The effects of trifluoroacetic acid (TFA) modulation, linker substitution, and MOF activation temperature on the pore structure and catalytic activity are evaluated. Differing trends in activity and thermal stability are observed for MOFs with ligand substitutions vs ones without. Optimal MOF activation temperatures vary based on linker substitution, though both substituted and unsubstituted linkers give rise to catalysts with high activity. Catalytic tests using sugars of different sizes suggest catalysis occurs in the micropores and/or mesopores of the MOF, though deposition of carbonaceous species on the MOF limits catalyst recyclability. The MOF system leads to improved product yields and different ratios of cyclized to uncyclized products compared to a homogeneous zirconium salt catalyst under similar conditions, suggesting the MOF catalysts may offer synthetic utility.

Current efforts in this laboratory continue to focus on the preparation of novel complexant motifs for potential use in chemoselective minor‐actinide liquid–liquid separations of relevant cations from used nuclear fuel. The present work describes an efficient Pd‐catalyzed amination reaction of diversely functionalized 6‐bromo‐1,2,4‐triazinyl‐pyridine scaffolds with various amines to afford the opportunity for convergent modulation of complexant electronic and steric properties directly from one substrate towards potentially enhanced solubility in process‐relevant solvents. The 21 novel examples presented highlight a unified approach to extensive molecular diversity and provide the ability to further study chelate effects, solubility properties, and complexation efficacy on nonsymmetric, moderately soft‐Lewis‐basic complexant scaffolds without the incorporation of additional heteroaromatic moieties. Synthetic‐method optimization, amine and scaffold scope, as well as a scale‐up experiment are presented.

No abstract

This work explores the efficacy of silica/organic hybrid catalysts, where the organic component is built from linear aminopolymers appended to the silica support within the support mesopores. Specifically, the role of molecular weight and polymer chain composition in amine-bearing atom transfer radical polymerization-synthesized poly(styrene-co-2-(4-vinylbenzyl)isoindoline-1,3-dione) copolymers is probed in the aldol condensation of 4nitrobenzaldehyde and acetone. Controlled polymerization produces protected amine-containing poly(styrene) chains of controlled molecular weight and dispersity, and a grafting-to thiol−ene coupling approach followed by a phthalimide deprotection step are used to covalently tether and activate the polymer hybrid catalysts prior to the catalytic reactions. Site-normalized batch kinetics are used to assess the role of polymer molecular weight and chain composition in the cooperative catalysis. Lower-molecular-weight copolymers are demonstrated to be more active than catalysts built from only molecular organic components or from highermolecular-weight chains. Molecular dynamics simulations are used to probe the role of polymer flexibility and morphology, whereby it is determined that higher-molecular-weight hybrid structures result in congested pores that inhibit active site cooperativity and the diffusivity of reagents, thus resulting in lower rates during the reaction.