Synthesis of the 1,5-Benzothiazepane Scaffold - Established Methods and New Developments

The 1,5-benzothiazepane structure is an important heterocyclic moiety present in a variety of commercial drugs and pharmaceuticals. This privileged scaffold exhibits a diversity of biological activities, including antimicrobial, antibacterial, anti-epileptic, anti-HIV, antidepressant, antithrombotic and anticancer properties. Its important pharmacological potential renders research into the development of new and efficient synthetic methods of high relevance. In the first part of this review, an overview of different synthetic approaches toward 1,5-benzothiazepane and its derivatives is provided, ranging from established protocols to recent (enantioselective) methods that promote sustainability. In the second part, several structural characteristics influencing biological activity are briefly explored, providing a few insights into the structure-activity relationships of these compounds.

Cooperativity in the Aldol Condensation Using Bifunctional Mesoporous Silica-Poly(styrene) MCM-41 Organic/Inorganic Hybrid Catalysts

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 4-nitrobenzaldehyde 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 higher-molecular-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.

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.

An efficient and sustainable catalytic reduction of carbon–carbon multiple bonds, aldehydes, and ketones using a Cu nanoparticle decorated metal organic framework

Economical, reusable, eco-friendly sustainable process is reported that involve low amount of hydrazine hydrate.

Conversion of methanol to propylene over nano-sized ZSM-5 zeolite aggregates synthesized by a modified seed-induced method with CTAB

Nano-sized ZSM-5 zeolite aggregates with mesopores and high catalytic activity were prepared by a modified seed-induced method using silicate-1 as seeds without additional templates in the presence of a trace amount of CTAB.