Ce-Containing MgAl-Layered Double Hydroxide-Graphene Oxide Hybrid Materials as Multifunctional Catalysts for Organic Transformations

The combination of layered double hydroxides (LDH) with graphene oxide (GO) enables the formation of nanohybrids with improved properties. This work focuses on the structural and catalytic properties of Ce-containing MgAl LDH-GO composites bearing different concentrations of GO in the range of 5-25 wt.%. The synthesis of the composites was performed by co-precipitating the LDH phase in the presence of GO, while their characterization was performed using XRF, XRD, DRIFT, Raman, SEM, nitrogen adsorption-desorption, and acidity-basicity measurements. The LDH-GO composites, showing redox, basic, and acid catalytic functions, were tested in two different types of organic transformations: (i) Knoevenagel condensation and (ii) one-pot cascade oxidation-Knoevenagel condensation. (i) The cinnamic acid was synthesized by the Knoevenagel condensation of benzaldehyde with diethylmalonate. The composites showed catalytic performances in strong contrast to neat LDH or GO, suggesting a synergistic interaction between the two components. During Knoevenagel condensation, the catalytic activity increased with the GO content in the hybrids up to 15 wt.% and decreased afterwards. (ii) 2-Benzoyl-3-phenylacrylonitrile was synthesized by the aerobic oxidation of benzyl alcohol followed by the Knoevenagel condensation with benzoyl acetonitrile using three different non-polar solvents, i.e., toluene, benzene, and mesitylene. The conversion of benzyl alcohol was higher for the hybrid materials compared to the individual components but decreased with the increase of the graphene oxide concentration.

Photo-on-Demand Synthesis of Vilsmeier Reagents with Chloroform and Their Applications to One-Pot Organic Syntheses

The Vilsmeier reagent (VR), first reported a century ago, is a versatile reagent in a variety of organic reactions. It is used extensively in formylation reactions. However, the synthesis of VR generally requires highly toxic and corrosive reagents such as POCl₃, SOCl₂, or COCl₂. In this study, we found that VR is readily obtained from a CHCl₃ solution containing N,N-dimethylformamide or N,N-dimethylacetamide upon photo-irradiation under O₂ bubbling. The corresponding Vilsmeier reagents were obtained in high yields with the generation of gaseous HCl and CO₂ as byproducts to allow their isolations as crystalline solid products amenable to analysis by X-ray crystallography. With the advantage of using CHCl₃, which bifunctionally serves as a reactant and a solvent, this photo-on-demand VR synthesis is available for one-pot syntheses of aldehydes, acid chlorides, formates, ketones, esters, and amides.

Versatile Bispidine-Based Bifunctional Chelators for 64 CuII -Labelling of Biomolecules

Bifunctional chelators as parts of modular metal-based radiopharmaceuticals are responsible for stable complexation of the radiometal ion and for covalent linkage between the complex and the targeting vector. To avoid loss of complex stability, the bioconjugation strategy should not interfere with the radiometal chelation by occupying coordinating groups. The C9 position of the very stable CuII chelator 3,7-diazabicyclo[3.3.1]nonane (bispidine) is virtually predestined to introduce functional groups for facile bioconjugation as this functionalisation does not disturb the metal binding centre. We describe the preparation and characterisation of a set of novel bispidine derivatives equipped with suitable functional groups for diverse bioconjugation reactions, including common amine coupling strategies (bispidine-isothiocyanate) and the Cu-free strain-promoted alkyne-azide cycloaddition. We demonstrate their functionality and versatility in an exemplary way by conjugation to an antibody-based biomolecule and validate the obtained conjugate in vitro and in vivo.

Combined structural and theoretical investigation on differently substituted bispidine ligands: predicting the properties of their corresponding coordination polymers

Pyridine-based bispidine ligands L1–L7 have been studied by single crystal X-ray diffraction and solid-state DFT calculations in an attempt to predict the dynamic properties of their corresponding Mn(ii) coordination polymers.

CuO-catalyzed oxidation of aryl acetates with aqueous tert-butyl hydroperoxide for the synthesis of α-ketoesters

A practical method to access α-ketoesters from readily available aryl acetates is developed. In this approach, aqueous tert-butyl hydroperoxide and CuO are employed. No additional solvents are required and it was found that the peroxide side products in the reaction can be decomposed by pyridine.

2,4-Substituted bispidines as rigid hosts for versatile applications: from κ-opioid receptor to metal coordination

Bispidines and their applications in medicine, catalysis, magnetism and medical imaging: what do we know about the influence of substituents?

Application of chiral bi- and tetra-dentate bispidine-derived ligands in the copper(ii)-catalyzed asymmetric Henry reaction

Rationalized bispidinone-based ligands were reacted with copper(ii) salts, which afforded effective catalysts for asymmetric Henry reactions.

H3PW12O40/mpg-C3N4 as an efficient and reusable bifunctional catalyst in one-pot oxidation–Knoevenagel condensation tandem reaction

A single-site bifunctional catalyst for oxidation–Knoevenagel condensation tandem reaction was prepared by immobilizing H₃PW₁₂O₄₀ on mpg-C₃N₄via electrostatic interaction.

Highly diastereoselective crystallization-induced asymmetric transformation of 1,3-disubstituted-tetrahydro-β-carbolines in water

A green and highly stereoselective method for the synthesis of cis or trans-1,3-disubstituted-tetrahydro-β-carbolines has been developed using water as the solvent.