Green production of limonene diepoxide for potential biomedical applications

Elucidating the Role of Water on Limonene Oxidation with H2O2 over γ-Al2O3

Limonene oxide, which is produced from limonene epoxidation, is a valuable molecule that can be applied in flavor, fragrance, and renewable polymer applications. A catalytic reaction system using H2O2 with γ-Al2O3 and ethyl acetate (EtOAc) as the solvent has been explored as an effective system for this reaction. In these previous studies, a number of postulates have been proposed as to how water affects the reaction; therefore, the focus of this work is to elucidate the role of water in limonene epoxidation. While not impacting the selectivity to limonene oxide, the amount of water in the reaction system is shown to significantly impact the limonene reactivity. Furthermore, through both addition of excess water and removal of water with a Dean-Stark apparatus, the control of the H2O2/H2O ratio is demonstrated to be the primary factor controlling reactivity. In contrast, changes in limonene concentrations for a specific H2O2/H2O ratio are shown to have little impact on the reaction rate. This study shows that the competitive adsorption of H2O2 and water on the catalyst surface is key in explaining the water impact on the reaction performance.

Integration of Design of Experiments, Analysis of Variance and Response Surface Methodology in Assessing Heterogeneous Catalysts Processes: A Minireview

This work reviews the application of Analysis of Variance (ANOVA), Design of Experiments (DOE), and Response Surface Methodology (RSM) in heterogeneous catalysis, based on an analysis of recent scientific literature. Heterogeneous catalysis plays a key role in various industries, guiding chemical reactions, optimizing the performance of different processes and/or prioritizing products, and ANOVA, DOE and RSM are valuable tools to understand the intricate relationships between catalyst properties, process variables and reaction responses. This understanding facilitates improvements in catalysts performance and selectivity, thereby optimizing processes. Drawing insights from recent studies, this minireview highlights the different applications of ANOVA-based experimental designs and RSM optimization techniques in catalytic process evaluation. Therefore, this review provides valuable insights into these current statistical methodologies applied to heterogeneous catalysis research, informing the relevance and future directions of the research in the field.

Stereospecific Epoxidation of Limonene Catalyzed by Peroxygenase from Oat Seeds

Limonene is one of the most abundant naturally occurring cyclic monoterpenes and has recently emerged as a sustainable alternative to petroleum-based solvents as well as a chemical platform for the production of value-added compounds. The biocatalytic epoxidation of both enantiomers of limonene was carried out in the presence of a peroxygenase-containing preparation from oat (Avena sativa) flour. Different reaction profiles were observed depending on the starting enantiomer of limonene, but in both cases the 1,2-monoepoxide was obtained as the main product with excellent diastereoselectivity. Trans-1,2-monoepoxide and cis-1,2-monoepoxide were isolated from the reaction of (R)-limonene and (S)-limonene, respectively, and the reactions were scaled-up to 0.17 M substrate concentration. The process is valuable for operational simplicity, lack of toxic metal catalysts, and cost-effectiveness of the enzymatic source. Pure stereoisomers of 1,2-monoepoxides of limonene constitute a useful starting material for biorenewable polymers, but can be also converted into other chiral derivatives by epoxide ring opening with nucleophiles. As a proof of concept, a tandem protocol for the preparation of enantiopure (1S,2S,4R)-1,2-diol from (R)-limonene and (1R,2R,4S)-1,2-diol from (S)-limonene was developed.

One-pot three-step mechanically assisted synthesis and catalytic performance of tripodal metallic complexes

All-green matters. Synthesis of the ligand and metal–ligand complexes and a model catalytic oxidation reaction can be sequentially processed under solventless conditions using a planetary ball mill, via fast, high yielding and selective processes.