CeO2-catalyzed Transformations of Nitriles and Amides

Abstract

Recently, cerium oxides have been extensively used as heterogeneous catalysts for green organic reactions. This review describes recent progress in such reactions, with a focus on our studies on pure CeO 2 -catalyzed reactions of nitriles and amides with nucleophiles (H 2 O, alcohols, and amines). Hydration of nitriles to amides in water, one-pot ester synthesis from nitriles and alcohols, one-pot synthesis of N-alkylamides from nitriles with amines, and synthesis of N-alkylamides from amides and amines (transamidation) are selectively catalyzed by CeO 2 under aqueous or solvent-free conditions. Mechanistic studies suggest that a cooperation of Lewis acid site (Ce 4+ cation) and acidbase (CeO) pair site plays essential roles in the catalytic reactions.

Direct Phenolysis Reactions of Unactivated Amides into Phenolic Esters Promoted by a Heterogeneous CeO2 Catalyst

“…Specifically, we observed good linearity with a positive slope ( ρ =+0.26) (Figure B), which indicates that a transition state in the rate‐limiting step of the phenolysis contains a negative charge at the α‐carbon atom adjacent to the benzene ring. Accordingly, it can be concluded that the nucleophilic addition of the phenoxide species to the activated carbonyl carbon atom of the amide proceeds via a negatively charged transition state, and that this could be the rate‐limiting step of this reaction …”

“…The phenolysis of para ‐substituted benzamides with phenol revealed a good relationship between log( k X / k H ) and the Brown–Okamoto parameter ( σ + ) . Specifically, we observed good linearity with a positive slope ( ρ =+0.26) (Figure B), which indicates that a transition state in the rate‐limiting step of the phenolysis contains a negative charge at the α‐carbon atom adjacent to the benzene ring.…”

“…Herein, we report a simple, additive‐free and reusable heterogenous catalytic system based on CeO 2 for the direct phenolysis of unactivated amides into the corresponding phenolic esters. A systematic mechanistic study revealed that the unique combination of acid/base and redox properties of CeO 2 promotes this esterification reaction. This catalytic system not only offers a facile means to cleave the amide C−N bond, but also significantly promotes the use of amides and phenols as important building blocks for the synthesis of valuable esters.…”

Zr‐MOF‐808 as Catalyst for Amide Esterification

“…Examples of this are picolinic acid or niacin derivate aromatic ester, which are active for apoptosis of human leukaemia cells and rubefacients prodrugs, respectively. 16,17 In nature, protease enzymes can perform peptide bond hydrolysis in proteins through an ATP-dependent process. Inspired by the confined space and active sites of these enzymes (based on transition metals), inorganic artificial systems have been synthesized.…”

Direct conversion of CO2 with diols, aminoalcohols and diamines to cyclic carbonates, cyclic carbamates and cyclic ureas using heterogeneous catalysts

“…For the catalysts containing Zr, the calcination temperature affording the maximum propylene carbonate amount was generally changed to higher one in comparison with pure CeO 2 in spite of the decrease in catalyst surface area. The active sites are thought to be weak acid–base sites on the plain crystalline surface. The active sites can be influenced by the bulk composition of Ce/Zr and more significantly by the surface composition.…”