A Dormant Reagent Reaction-Diffusion Method for the Generation of Co-Fe Prussian Blue Analogue Periodic Precipitate Particle Libraries

Liesegang patterns that develop as a result of reaction-diffusion can simultaneously form products with slightly different sizes spatially separated in a single medium. We show here a reaction-diffusion method using a dormant reagent (citrate) for developing Liesegang patterns of cobalt hexacyanoferrate Prussian Blue analog (PBA) particle libraries. This method slows the precipitation reaction and produces different-sized particles in a gel medium at different locations. The gel-embedded particles are still catalytically active. Finally, the applicability of the new method to other PBAs and 2D systems is presented. The method proves promising for obtaining similar inorganic framework libraries with catalytic abilities.

One-pot double annulations to confer diastereoselective spirooxindolepyrrolothiazoles

A novel four-component reaction in one pot as an atom- and step-economic process was developed to synthesize diastereoselectively spirooxindolepyrrolothiazoles through sequential N,S-acetalation of aldehydes with cysteine and decarboxylative [3 + 2] cycloaddition with olefinic oxindoles. High synthetic efficiency, operational simplification and reaction process economy using EtOH as solvent, and only releasing CO2 and H2O as side products confer this approach favorable in green chemistry metrics analysis.

A CeCoOx Core/Nb2 O5 @TiO2 Double-Shell Nanocage Catalyst Demonstrates High Activity and Water Resistance for Catalytic Combustion of o-Dichlorobenzene

A series of catalysts with different core-shell structures has been successfully prepared by a hydrothermal method. They consisted of CeCoO_x @TiO₂ (single shell), CeCoO_x @Nb₂ O₅ (single shell) and CeCoO_x @Nb₂ O₅ @TiO₂ (double shell) core-shell nanocages and CeCoO_x nanocages, in which CeCoO_x was the core and TiO₂ and Nb₂ O₅ were shells. The influence of the core-shell structure on the catalytic performance of o-dichlorobenzene was investigated by activity, water-resistance, and thermal stability tests as well as catalyst characterization. The temperatures corresponding to 90 % conversion of o-dichlorobenzene (T₉₀ ) of CeCoO_x , CeCoO_x @TiO₂ , CeCoO_x @Nb₂ O₅ , and CeCoO_x @Nb₂ O₅ @TiO₂ catalysts were 415, 383, 362 and 367 °C, respectively. CeCoO_x @Nb₂ O₅ exhibited excellent catalytic activity, mainly owing to the special core-shell structure, large specific surface area, abundant activity of Co³⁺ , Ce³⁺ , Nb⁵⁺ , strong reducibility, and more active oxygen vacancies. It can be seen that the Nb₂ O₅ coating can greatly improve the catalytic activity of the catalyst. In addition, due to the protective effect of the TiO₂ shell on CeCoO_x , CeCoO_x @Nb₂ O₅ @TiO₂ catalysts exhibited outstanding thermal and hydrothermal stability for 20 hours. The T₉₀ of CeCoO_x @Nb₂ O₅ @TiO₂ was slightly lower than that of CeCoO_x @Nb₂ O₅ , but it had higher stability and hydrothermal stability. Furthermore, possible reaction pathways involving the Mars-van-Krevelen (MvK) and Langmuir-Hinshelwood (L-H) models were deduced based on studies of the temperature-programmed desorption of O₂ (O₂ -TPD), X-ray photoelectron spectroscopy (XPS), and in situ diffuse reflectance FTIR spectroscopy (DRIFTS) characterization.

Wolf-Lamb-type Catalysis in One Pot Using Electrospun Polymeric Catalyst Membranes

Multistep catalytic transformations using incompatible catalysts (Wolf-Lamb-type) in a one-pot reaction cascade require site isolation of different catalysts by compartmentalization. In this work, the use of different electrospun catalytic membranes in a modular way as individual compartments is shown for one-pot Wolf-Lamb-type reaction cascades. The data are presented for one-pot cascade reaction sequences catalyzed by acidic and basic membranes made by electrospinning polymeric acid (poly(styrene-co-styrene sulfonic acid-co-4-methacryloyl-oxybenzophen)) and basic (poly(styrene-co-4-vinylpyridine-co-4-methacryloyl-oxybenzophen)) catalysts, respectively. The two-step, one-pot system used is the acidic catalyzed deacetylation of dimethoxybenzylacetale to benzaldehyde, which reacts with ethyl cyanoformate to result in a high yield of product (over 90%) under base-catalyzed conditions. The reaction kinetics are further monitored and evaluated by using differential equations, showing the necessity of a parameter Δt to represent a retarded start for the second reaction step. The concept provides an easy and upscalable approach for use in Wolf-Lamb-type systems.

Permeable Self-Assembled Molecular Containers for Catalyst Isolation Enabling Two-Step Cascade Reactions

Establishment of a general one-pot cascade reaction protocol would dramatically reduce the effort of multistep organic synthesis. We demonstrate that the unique structure of M₁₂L₂₄ self-assembled complexes gives them the potential to serve as catalyst carriers for enabling continuous chemical transformations. A stereoselective cascade reaction (allylic oxidation followed by Diels-Alder cyclization) with two intrinsically incompatible catalysts was demonstrated. Our system is advantageous in terms of availability, scalability, and predictability.

Application of Ionic Liquids in Pot-in-Pot Reactions

Pot-in-pot reactions are designed such that two reaction media (solvents, catalysts and reagents) are isolated from each other by a polymeric membrane similar to matryoshka dolls (Russian nesting dolls). The first reaction is allowed to progress to completion before triggering the second reaction in which all necessary solvents, reactants, or catalysts are placed except for the starting reagent for the target reaction. With the appropriate trigger, in most cases unidirectional flux, the product of the first reaction is introduced to the second medium allowing a second transformation in the same glass reaction pot--albeit separated by a polymeric membrane. The basis of these reaction systems is the controlled selective flux of one reagent over the other components of the first reaction while maintaining steady-state catalyst concentration in the first "pot". The use of ionic liquids as tools to control chemical potential across the polymeric membranes making the first pot is discussed based on standard diffusion models--Fickian and Payne's models. Besides chemical potential, use of ionic liquids as delivery agent for a small amount of a solvent that slightly swells the polymeric membrane, hence increasing flux, is highlighted. This review highlights the critical role ionic liquids play in site-isolation of multiple catalyzed reactions in a standard pot-in-pot reaction.

Polyurethane nanomicelles: a novel eco-friendly and efficient polymeric ionic solvent for the Cannizzaro reaction

The Cannizzaro reaction is performed under very mild alkaline conditions using anionic polyurethane nanomicelles as a novel reusable polymeric ionic solvent.