Monthly Archives: September 2023

Rongalite as a Versatile Reagent in Organic Synthesis

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Rongalite as a Versatile Reagent in Organic Synthesis†

This review presents the comprehensive progress in the utilization of rongalite as a versatile reagent in organic synthesis in recent years.


Comprehensive Summary

This review provides a comprehensive summary of progress to date in the utilization of rongalite as a versatile reagent in organic synthesis, with a focus on recent researches. The contents have been organized according to the functions exhibited by rongalite. Reaction mechanisms are provided, demonstrating the multifaceted roles of this compound in various transformations, including as a sulfone, C1 or masked proton source and as a single electron donor or reducing agent.

Light‐Induced Domino and Multicomponent Reactions: How to Reach Molecular Complexity without a Catalyst

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Light-Induced Domino and Multicomponent Reactions: How to Reach Molecular Complexity without a Catalyst

Is it possible to build up molecular complexity without the help of a catalyst? Yes, it is! With the suitable starting-materials, a domino or multicomponent reaction can be initiated just turning on the right light.


Abstract

Achieving high molecular complexity can be not trivial, but the exploitation of domino reactions provides an atom- and step-economical method to reach this target. Over the past decades, a lot of efforts have been put on the development of photocatalytic cascades employing both metal-based and purely organic catalysts. Despite the effectiveness of these protocols, catalyst- and additive-free light-induced domino reactions are gaining momentum thank to their efficiency, operational simplicity and sustainability. The increasing number of papers published on this field in the last years is a proof of the appeal of these transformations. In this Review, we discuss domino and multicomponent reactions mediated by light with a focus on photocatalyst- and additive-free processes. The most recent advances in the synthesis of complex nitrogen-, oxygen-, sulphur- and selenium-heterocycles together with multicomponent cascades are analysed with an emphasis on both experimental and mechanistic studies.

Counter‐Anions Rendered Weak‐Interactions Perturb the Stability of Tyrosinase‐Mimicked Peroxo‐Dicopper(II) Active Site: Unraveling Computational Indicators

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Counter-Anions Rendered Weak-Interactions Perturb the Stability of Tyrosinase-Mimicked Peroxo-Dicopper(II) Active Site: Unraveling Computational Indicators

Counter-anions (PhCO2 −, CF3SO3 −, TsO−, and SbF6 −) perturb the stability of the tyrosinase's biomimetic model (PT ). In this work, we showcase that the Gibbs energies, Cu2O2 and counter-anion distances, IGMH-based δGPair values, orbitals overlap between Cu2O2 and counter-anion, Cu2O2 bending angles, and distortion-interaction energies are computational indicators to predict the stability of PT in presence of counter anions.


Abstract

It has been observed in literature that the stability of tyrosinase-mimicked μ-η2:η2-peroxo-dicopper(II) (P) can be perturbed in presence of counter-anions (CAs) such as PhCO2 −, CF3SO3 −, TsO− and SbF6 −. In this work, we unravel computational indicators using density functional theory to screen and study the stability of P in experimentally-reported cases. These indicators are Gibbs energies, geometrical parameters such as distances and angles, independent gradient model based on Hirshfeld partition (IGMH) generated data, orbitals’ overlap, and distortion-interaction (DI) energies. Our DFT computed Gibbs energies indicate that P is stable in case of PhCO2 − and TsO−. CF3SO3 − allows P and its isoelectronic species bis-μ-oxo-dicopper (O) to coexist. SbF6 − shows that O is in excess. Our indicators reveal that the stability of P in case of PhCO2 − and TsO− is due to the better placing of P and its CA, thus leading to better interactions and overlap of orbitals. Other indicator displays that the plane of Cu2O2 core in P is more bend in PhCO2 − and TsO− cases as compared to the plane in the other two cases. In addition, the IGMH-based indicator displays higher values in the case of PhCO2 − and TsO− than the other CAs.

Eco‐friendly Synthesis of Silver Nanoparticles and its Application in Hydrogen Photogeneration and Nanoplasmonic Biosensing

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Eco-friendly Synthesis of Silver Nanoparticles and its Application in Hydrogen Photogeneration and Nanoplasmonic Biosensing

Silver NPs between 7.0 and 12.8 nm in size are prepared in diluted aqueous solutions containing only radish extracts or honey by microwave irradiation. The AgNPs are assembled in a nanoplasmonic biosensor chip for biomarkers detections and used as co-photocatalyst (TiO2@AgNPs) for hydrogen generation using UV or visible light.


Abstract

Environmentally friendly methods for silver nanoparticles (AgNPs) synthesis without the use of hazardous chemicals have recently drawn attention. In this work, AgNPs have been synthesized by microwave irradiation using only honey solutions or aqueous fresh pink radish extracts. The concentrations of honey, radish extract, AgNO3 and pH were varied. AgNPs presented mean sizes between 7.0 and 12.8 nm and were stable up to 120 days. The AgNPs were employed as co-catalyst (TiO2@AgNPs) to increase the hydrogen photogeneration under UV-vis and only visible light irradiation, when compared to pristine TiO2 NPs. The prepared photocatalyst also showed hydrogen generation under visible light. Additionally, AgNPs were used to assemble a nanoplasmonic biosensor for the biodetection of extremely low concentrations of streptavidin, owing to its specific binding to biotin. It is shown here that green AgNPs are versatile nanomaterials, thus being potential candidates for hydrogen photogeneration and biosensing applications.

Protocell Communication through the Eyes of Synthetic Organic Chemists

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Protocell Communication through the Eyes of Synthetic Organic Chemists

In this Concept, the bio-derived signal transduction machineries utilised for protocell communication are reviewed and categorised into enzyme cascades, DNA strand displacement, and gene-mediated systems. Future opportunities for synthetic chemists to develop new bio-inspired and fully synthetic alternatives to these bio-derived machineries in the form of synthetic enzymes or “synzymes” are highlighted.


Abstract

The bottom-up fabrication of synthetic cells (protocells) from molecules and materials, is a major challenge of modern chemistry. A significant breakthrough has been the engineering of protocells capable of chemical communication using bio-derived molecules and ex situ stabilised cell machineries. These, however, suffer from short shelf-lives, high costs, and require mild aqueous conditions. In this Concept Article we analyse the chemistry at the heart of protocell communication to highlight new opportunities for synthetic chemists in protocell engineering. Specifically, we (i) categorise the main bio-derived chemical communication machineries in enzyme cascades, DNA strand displacement, and gene-mediated communication; (ii) review the chemistries of these signal transduction machineries; and (iii) introduce new types of bio-inspired, fully synthetic artificial enzymes to replace their natural counterparts. Developing protocells that incorporate synthetic analogues of bio-derived signal transduction machineries will improve the robustness, stability, and versatility of protocells, and broaden their applications to highly strategic fields such as photocatalysis and fine chemicals production.

Multienzymatic Synthesis of γ‐Lactam Building Blocks from Unsaturated Esters and Hydroxylamine

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Multienzymatic Synthesis of γ-Lactam Building Blocks from Unsaturated Esters and Hydroxylamine

N-hydroxy-γ-lactams are produced through an enzymatic sequence combining a lipase-catalyzed hydroxylamidation with an oxidase/peroxidase-induced ene-type cyclization. This methodology provides a mild and scalable access to N-heterocyclic building blocks from basic γ,δ-unsaturated esters and aqueous hydroxylamine, and its utility is illustrated by the formal total synthesis of the tetracyclic alkaloid cephalotaxine.


Abstract

The assembly of enzymatic cascades and multi-step reaction sequences represents an attractive alternative to traditional synthetic-organic approaches. The biocatalytic reaction mediators offer not only mild conditions and permit the use of environmentally benign reagents, but the high compatibility of different enzymes promises more streamlined reaction setups. In this study, a triple-enzymatic strategy was developed that enables the direct conversion of γ,δ-unsaturated esters to N-hydroxy-γ-lactam building blocks. Hereby, a lipase-catalyzed hydroxylaminolysis generates hydroxamic acid intermediates that are subsequently aerobically activated by horseradish peroxidase and glucose oxidase to cyclize in an intramolecular nitroso ene reaction. Utilizing the hydroxylaminolysis/ene-cyclization sequence for the preparation of an aza-spirocyclic lactam, the multi-enzymatic methodology was successfully employed in the synthesis of key intermediates en route to alkaloids of the Cephalotaxus family.

Research Progress on Spider‐Inspired Tough Fibers

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Research Progress on Spider-Inspired Tough Fibers†


Comprehensive Summary

Spider silk has attracted increasing attention due to its fascinating combination of ultra-high tenacity high strength, and excellent elasticity. Based on the fundamental biological studies on spider silk, significant research efforts have been devoted to biotechnology and chemical synthesis to mimic or even exceed the properties of natural spider silk fibers. Moreover, the natural spider silk fiber has been simulated with the burgeoning development of numerous spinning technologies, including wet spinning, dry spinning, electrostatic spinning, and microfluidic spinning, which continuously help to optimize the properties of synthetic spider silk. The unique characteristics of natural spider silk include high refraction transmission, heat resistance, antimicrobial properties, biocompatibility, and super shrinking. Biconical recreation of spider silk with special features and extraordinary capabilities demonstrates potential applications in biomedicine, smart wearables, artificial muscles and sensors, aerospace and other domains.

Alcohol‐Treated Nickel‐Aluminum Catalyst for One‐Step Highly‐Selective Butane‐1,4‐Diol Synthesis from 2‐Butyne‐1,4‐Diol

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The development of low-cost nickel-based catalysts for direct and selective hydrogenation of 2-butyne-1,4-diol (BYD) to butane-1,4-diol (BAD) under mild conditions is an important and attractive target both in fundamental research and industrialization but remains a formidable challenge. The primary industrial production method for BAD synthesis is a two-step reaction route, which suffers from complicated catalysis conditions and high equipment costs. Herein, we develop a high-performance catalyst via a facile alcohol-treated strategy for highly selective BAD synthesis at moderate operation conditions. The as-synthesized NA-80E catalyst exhibits outstanding BAD selectivity of 98.82% and BYD conversion of 100% at 60 oC and 4 MPa, outperforming most reported results for BAD formation in a one-step process and even being comparable to those obtained by the two-step hydrogenation reaction route under much high temperatures and pressures. Crucially, we found that after facile alcohol (ethanol) treatment, an intriguing phenomenon of suppression of adjacent acid-assisted hydrogenolysis via extra acidic Al species at the NiO-Al2O3 interface is observed, contributing to the precise enhancement of BAD selectivity by inhibiting the production of butanol (BOL). This facile alcohol-treated method along with the revealed mechanism of blocked hydrogenolysis opens vast possibilities for designing high-performance and highly-selective hydrogenation catalysts.

The Catalytic Function of Phosphorus Enriched on the Surface of Vanadium‐based Catalysts in Selective Oxidations

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The Catalytic Function of Phosphorus Enriched on the Surface of Vanadium-based Catalysts in Selective Oxidations

In this work, the variation of the phosphorus content on the surface of vanadium-based bulk catalysts by atomic layer deposition is used to experimentally unravel its catalytic functionality in the selective oxidation of n-butane. The consecutive combustion of maleic anhydride is suppressed, due to a surface enrichment with phosphorus.


Abstract

Vanadium phosphates are established as the benchmark system for the selective oxidation of n-butane towards maleic anhydride. By varying the phosphorus content on the surface of three V-based catalysts with diverse performance, this study experimentally elaborates on the catalytic function of phosphorus. Contact time variation and cofeed studies revealed, that surface phosphates, deposited in sub-monolayers via atomic layer deposition, significantly contribute to an increased product selectivity. Furthermore, our results suggest that the phosphorus particularly suppresses the consecutive combustion of the (re-)adsorbed product. The recently introduced solid solution catalyst V1-xNbxOPO4 with medium maleic anhydride selectivity could be tuned by the surface enrichment with phosphorus towards product selectivities of up to SMAN=60 %, under optimized alkane-rich feed conditions. Therefore, POx-V0.3Nb0.7OPO4 is introduced as promising catalyst, which is not based on vanadyl(IV) pyrophosphate, to access significantly higher MAN formation rates at increased alkane partial pressures of c n-butane>10 %vol in n-butane oxidation.