Bridging the gap between transition metal- and bio-catalysis via aqueous micellar catalysis

Imine Reductase-Catalyzed Remote Stereocontrol for Enantiodivergent Synthesis of Cyclohexylidene-Based Axially Chiral Amines

Cyclohexylidene-based amines exhibit unique axial chirality arising from the restricted double bond and have shown great potential in medicinal chemistry. However, their asymmetric synthesis remains challenging due to the long distance between the chirally relevant groups. Herein, we report a highly efficient and asymmetric synthesis of cyclohexylidene-based axially chiral amines from 4-substituted cyclohexanones and primary amines catalyzed by imine reductases (IREDs). Enantiodivergent IREDs were identified to provide convenient access to both enantiomers of chiral products with high yields and enantioselectivity (up to 99% yield, 99:1 or 1:99 enantiomeric ratio). A gram-scale synthesis of cyclohexylidene-based amines was also achieved. Moreover, protein X-ray crystallography and molecular modeling studies were conducted to provide structural insight into the remote stereocontrol of IREDs in generating cyclohexylidene-based axial chirality.

Two-Phase Epoxidations with Micellar Catalysts: Insights, Limitations, and Perspectives

Biphasic molecular catalysis is a promising strategy for combining catalyst recycling with the synthesis of advanced chemical products. The anchoring of catalysts to surfactants in water allows for both catalyst solubility in aqueous media and a simple separation from the organic product. In biphasic epoxidations, this approach allows the use of environmentally benign hydrogen peroxide as oxidant. However, challenges remain due to mass transport limitations between the aqueous and organic phase, incompatibilities in the multicomponent system, and side reactions in the acidic medium. Hence, the development of surface-active catalysts that enable controlled phase separation from all other components is highlighted in this concept article.

Micelle-enabled bromination of α-oxo ketene dithioacetals: mild and scalable approach via enzymatic catalysis

The bromination of α-oxo ketene dithioacetals using KBr/H2O2, catalyzed by Curvularia inaequalis vanadium chloroperoxidase (CiVCPO), has been successfully demonstrated. A comparative study of enzymatic processes "on water" versus "in water", using 2 wt% of the surfactant TPGS-750-M revealed that the in-water protocol not only provides higher yields but also accommodates a broader substrate scope. This bromination method in an aqueous micellar medium enabled the preparation of brominated α-oxo ketene dithioacetals in fair to excellent yields (23 examples). In the micellar system, the substrate concentration was increased up to 50 mM, and the amounts of the brominating agents KBr and H2O2 were reduced to approximately 2.0 equivalents without compromising efficiency. Notably, this process allows for the gram-scale preparation of brominated α-oxo ketene dithioacetals in high yields. Key advantages of this method include its benign and eco-friendly nature, the use of water as a green solvent, and its potential for large-scale production of brominated α-oxo ketene dithioacetals.

6-Hydroxy Picolinohydrazides Promoted Cu(I)-Catalyzed Hydroxylation Reaction in Water: Machine-Learning Accelerated Ligands Design and Reaction Optimization

Hydroxylated (hetero)arenes are privileged motifs in natural products, materials, small-molecule pharmaceuticals and serve as versatile intermediates in synthetic organic chemistry. Herein, we report an efficient Cu(I)/6-hydroxy picolinohydrazide-catalyzed hydroxylation reaction of (hetero)aryl halides (Br, Cl) in water. By establishing machine learning (ML) models, the design of ligands and optimization of reaction conditions were effectively accelerated. The N-(1,3-dimethyl-9H- carbazol-9-yl)-6-hydroxypicolinamide (L32, 6-HPA-DMCA) demonstrated high efficiency for (hetero)aryl bromides, promoting hydroxylation reactions with a minimal catalyst loading of 0.01 mol % (100 ppm) at 80 °C to reach 10000 TON; for substrates containing sensitive functional groups, the catalyst loading needs to be increased to 3.0 mol % under near-room temperature conditions. N-(2,7-Di-tert-butyl-9H-carbazol-9-yl)-6-hydroxypicolinamide (L42, 6-HPA-DTBCA) displayed superior reaction activity for chloride substrates, enabling hydroxylation reactions at 100 °C with 2-3 mol % catalyst loading. These represent the state of art for both lowest catalyst loading and temperature in the copper-catalyzed hydroxylation reactions. Furthermore, this method features a sustainable and environmentally friendly solvent system, accommodates a wide range of substrates, and shows potential for developing robust and scalable synthesis processes for key pharmaceutical intermediates.

Reactions of In Situ-Generated Difluorocarbene (:CF2) with Aromatic/Heteroaromatic Alcohols, Thiols, Olefins, and Alkynes under Environmentally Responsible Conditions

Environmentally respectful methods for generating and utilizing difluorocarbene (:CF2) in the synthesis of a wide array of valuable difluoromethylated compounds are disclosed. In particular, the insertion of the CF2 moiety into aromatic/heteroaromatic alcohols, thiols, olefins, and alkynes under neat or aqueous micellar catalysis conditions is demonstrated. These methods yield both satisfactory results and significantly lower E-Factors compared to traditional synthetic approaches. Key applications of these methodologies include optimization en route to a pantoprazole intermediate and development of a representative one-pot chemoenzymatic sequence. Additionally, analysis via calorimetry indicates no significant safety risk in the context of the developed solvent-free conditions.

Micelle-Assisted C(sp2)-H Functionalization for C-Se and C-X Bond Formation in the Aqueous Medium

An environmentally sustainable, versatile, and cost-effective approach for C-Se and C-X (X = I, Br, and Cl) bond formation through C-H functionalization assisted by micellar catalysis in water is developed. The reaction utilizes a minimum amount of diorganyl diselenides and potassium halides for the respective functionalizations. The present protocol was suitable for scale-up synthesis, which directly provided the desired selenylated products without the need for chromatographic purification, in sufficient purity. The aqueous micellar catalysis system was reusable for up to 5 reaction cycles without compromising the reaction yield.

Dilute suspensions of Janus rods: the role of bond and shape anisotropy

Nanometer-sized clusters are often targeted due to their potential applications as nanoreactors or storage/delivery devices. One route to assemble and stabilize finite structures consists of imparting directional bonding patterns between the nanoparticles. When only a portion of the particle surface is able to form an inter-particle bond, finite-size aggregates such as micelles and vesicles may form. Building on this approach, we combine particle shape anisotropy with the directionality of the bonding patterns and investigate the combined effect of particle elongation and surface patchiness on the low density assembly scenario. To this aim, we study the assembly of tip-functionalised Janus hard spherocylinders by means of Monte Carlo simulations. By exploring the effects of changing the interaction strength and range at different packing fractions, we highlight the role played by shape and bond anisotropy on the emerging aggregates (micelles, vesicles, elongated micelles, and lamellae). We observe that shape anisotropy plays a crucial role in suppressing phases that are typical to spherical Janus nanoparticles and that a careful tuning of the interaction parameters allows promoting the formation of spherical micelles. These finite-size spherical clusters composed of elongated particles might offer more interstitials and larger surface areas than those offered by micelles of spherical or almost-spherical units, thus enhancing their storage and catalytic properties.

Waste Valorization in a Sustainable Bio-Based Economy: The Road to Carbon Neutrality

The development of sustainable chemistry underlying the quest to minimize and/or valorize waste in the carbon-neutral manufacture of chemicals is followed over the last four to five decades. Both chemo- and biocatalysis have played an indispensable role in this odyssey. in particular developments in protein engineering, metagenomics and bioinformatics over the preceding three decades have played a crucial supporting role in facilitating the widespread application of both whole cell and cell-free biocatalysis. The pressing need, driven by climate change mitigation, for a drastic reduction in greenhouse gas (GHG) emissions, has precipitated an energy transition based on decarbonization of energy and defossilization of organic chemicals production. The latter involves waste biomass and/or waste CO2 as the feedstock and green electricity generated using solar, wind, hydroelectric or nuclear energy. The use of waste polysaccharides as feedstocks will underpin a renaissance in carbohydrate chemistry with pentoses and hexoses as base chemicals and bio-based solvents and polymers as environmentally friendly downstream products. The widespread availability of inexpensive electricity and solar energy has led to increasing attention for electro(bio)catalysis and photo(bio)catalysis which in turn is leading to myriad innovations in these fields.

Impact of water and oleic acid on glycerol monooleate phase transition and bi-continuous structure formation in white oil

Production of biofuels from biological feedstocks, such as soybean oil, is an important piece of the transition to renewable energy sources. Processes have been developed to co-refine these feedstocks with traditional feedstocks, however, the high concentration of polar functional groups in biofeedstocks can cause a wide range of intermediate chemical reactions and interactions. An improved understanding of the interactions of biofeedstocks and their degradation products is needed to continue to expand the usage of biofeedstocks in fuel production. In this study, the equilibrium structures of glycerol monooleate (GMO), a common intermediate product of biofeedstock processing, in white mineral oil at a wide range of compositions, temperatures, and additional byproduct concentrations (water and/or oleic acid) were characterized using small angle X-ray scattering (SAXS). It was determined that GMO can exist as crystalline aggregates in white oil or as reverse micelles depending on the concentration and temperature. The critical micelle temperature increases significantly with increasing GMO concentration but remains relatively stable with increasing water or fatty acid concentration. Fitting of the SAXS data revealed that for many compositions, the GMO formed roughly spherical reverse micelles, however, at high water concentrations (∼1 wt%), the GMO formed elongated reverse micelles. Additionally, when >1 wt% oleic acid was added to the system, bi-continuous structures were stabilized rather than discreet reverse micelles. These results help increase our understanding of the structural behavior of biofeedstock intermediate products at concentrations and temperatures relevant to biofuel production and can enable processers to design systems and products that can either leverage or prevent these interactions for improved processing performance.

Micelle-mediated synthesis of quinoxaline, 1,4-benzoxazine and 1,4-benzothiazine scaffolds from styrenes

A range of heterocycles based on quinoxalines, 1,4-benzoxazines and 1,4-benzothiazines have been accessed from styrenes by reacting them with benzene-1,2-diamine, 2-aminophenol and 2-aminothiophenol respectively in micellar medium. This reaction occurring in a less explored cetylpyridinium bromide (CPB) micellar medium operates in the presence of NBS through a tandem hydrobromination-oxidation cascade, converting styrenes to phenacyl bromides. Its subsequent nucleophilic addition with aromatic 1,2-dinucleophiles and further transformations led to the formation of heterocyclic constructs. The locus of the reaction site was confirmed through NMR studies and the types of interactions between the CPB and solubilizates were established by DFT calculations.

A bioinspired bifunctional catalyst: an amphiphilic organometallic catalyst for ring-closing metathesis forming liquid droplets in aqueous media

Inspired by phase-separated biopolymers with enzymatic activity, we developed an amphiphilic catalyst consisting of alternating hydrophilic oligo(ethylene glycol) and hydrophobic aromatic units bearing a Hoveyda-Grubbs catalyst center (MAHGII). MAHGII served as both a droplet-forming scaffold and a catalyst for ring-closing metathesis reactions, providing a new biomimetic system that promotes organic reactions in an aqueous environment.

One-pot chemo- and photo-enzymatic linear cascade processes

The combination of chemo- and photocatalyses with biocatalysis, which couples the flexible reactivity of the photo- and chemocatalysts with the highly selective and environmentally friendly nature of enzymes in one-pot linear cascades, represents a powerful tool in organic synthesis. However, the combination of photo-, chemo- and biocatalysts in one-pot is challenging because the optimal operating conditions of the involved catalyst types may be rather different, and the different stabilities of catalysts and their mutual deactivation are additional problems often encountered in one-pot cascade processes. This review explores a large number of transformations and approaches adopted for combining enzymes and chemo- and photocatalytic processes in a successful way to achieve valuable chemicals and valorisation of biomass. Moreover, the strategies for solving incompatibility issues in chemo-enzymatic reactions are analysed, introducing recent examples of the application of non-conventional solvents, enzyme-metal hybrid catalysts, and spatial compartmentalization strategies to implement chemo-enzymatic cascade processes.

Chemoenzymatic Synthesis of 2-Aryl Thiazolines from 4-Hydroxybenzaldehydes Using Vanillyl Alcohol Oxidases

Nitrogen heterocycles are commonly found in bioactive natural products and drugs. However, the biocatalytic tools for nitrogen heterocycle synthesis are limited. Herein, we report the discovery of vanillyl alcohol oxidases (VAOs) as efficient biocatalysts for the one-pot synthesis of 2-aryl thiazolines from various 4-hydroxybenzaldehydes and aminothiols. The wild-type biocatalyst features a broad scope of 4-hydroxybenzaldehydes. Though the scope of aminothiols is limited, it could be improved via semi-rational protein engineering, generating a variant to produce previously inaccessible cysteine-derived bioactive 2-aryl thiazolines using the wild-type VAO. Benefiting from the derivatizable functional groups in the enzymatic products, we further chemically modified these products to expand the chemical space, offering a new chemoenzymatic strategy for the green and efficient synthesis of structurally diverse 2-aryl-thiazoline derivatives to prompt their use in drug discovery and catalysis.

Merging High-Pressure Syngas Metal Catalysis and Biocatalysis in Tandem One-Pot Processes for the Synthesis of Nonchiral and Chiral Alcohols from Alkenes in Water

While simultaneously proceeding reactions are among the most fascinating features of biosynthesis, this concept of tandem processes also offers high potential in the chemical industry in terms of less waste production and improved process efficiency and sustainability. Although examples of one-pot chemoenzymatic syntheses exist, the combination of completely different reaction types is rare. Herein, we demonstrate that extreme "antipodes" of the "worlds of catalysis", such as syngas-based high-pressure hydroformylation and biocatalyzed reduction, can be combined within a tandem-type one-pot process in water. No significant deactivation was found for either the biocatalyst or the chemocatalyst. A proof-of-concept for the one-pot process starting from 1-octene was established with >99 % conversion and 80 % isolated yield of the desired alcohol isomers. All necessary components for hydroformylation and biocatalysis were added to the reactor from the beginning. This concept has been extended to the enantioselective synthesis of chiral products by conducting the hydroformylation of styrene and an enzymatic dynamic kinetic resolution in a tandem mode, leading to an excellent conversion of >99 % and an enantiomeric ratio of 91 : 9 for (S)-2-phenylpropanol. The overall process runs in water under mild and energy-saving conditions, without any need for intermediate isolation.

Simple Sol-Gel Protein Stabilization toward Rainbow and White Lighting Devices

Fluorescent proteins (FPs) are heralded as a paradigm of sustainable materials for photonics/optoelectronics. However, their stabilization under non-physiological environments and/or harsh operation conditions is the major challenge. Among the FP-stabilization methods, classical sol-gel is the most effective, but less versatile, as most of the proteins/enzymes are easily degraded due to the need of multi-step processes, surfactants, and mixed water/organic solvents in extreme pH. Herein, sol-gel chemistry with archetypal FPs (mGreenLantern; mCherry) is revisited, simplifying the method by one-pot, surfactant-free, and aqueous media (phosphate buffer saline pH = 7.4). The synthesis mechanism involves the direct reaction of the carboxylic groups at the FP surface with the silica precursor, generating a positively charged FP intermediate that acts as a seed for the formation of size-controlled mesoporous FP@SiO2 nanoparticles. Green-/red-emissive (single-FP component) and dual-emissive (multi-FPs component; kinetic studies not required) FP@SiO2 are prepared without affecting the FP photoluminescence and stabilities (>6 months) under dry storage and organic solvent suspensions. Finally, FP@SiO2 color filters are applied to rainbow and white bio-hybrid light-emitting diodes featuring up to 15-fold enhanced stabilities without reducing luminous efficacy compared to references with native FPs. Overall, an easy, versatile, and effective FP-stabilization method is demonstrated in FP@SiO2 toward sustainable protein lighting.

Design of 3D-Printed Heterogeneous Reactor Systems To Overcome Incompatibility Hurdles when Combining Metal and Enzyme Catalysis in a One-Pot Process

Combining chemo- and biocatalysis enables the design of novel economic and sustainable one-pot processes for the preparation of industrial chemicals, preferably proceeding in water. While a range of proofs-of-concept for the compatibility of such catalysts from these two different "worlds of catalysis" have recently been demonstrated, merging noncompatible chemo- and biocatalysts for joint applications within one reactor remained a challenge. A conceptual solution is compartmentalization of the catalytic moieties by heterogenization of critical catalyst components, thus "shielding" them from the complementary noncompatible catalyst, substrate or reagent. Exemplified for a one-pot process consisting of a metal-catalyzed Wacker oxidation and enzymatic reduction as noncompatible individual reactions steps, we demonstrate that making use of 3D printing of heterogeneous materials containing Cu as a critical metal component can overcome such incompatibility hurdles. The application of a 3D-printed Cu-ceramic device as metal catalyst component allows an efficient combination with the enzyme and the desired two-step transformation of styrene into the chiral alcohol product with high overall conversion and excellent enantioselectivity. This compartmentalization concept based on 3D printing of heterogenized metal catalysts represents a scalable methodology and opens up numerous perspectives to be used as a general tool also for other related chemoenzymatic research challenges.

Spatially Confined Nanoreactors Designed for Biological Applications

The applications of nanoreactors in biology are becoming increasingly significant and prominent. Specifically, nanoreactors with spatially confined, due to their exquisite design that effectively limits the spatial range of biomolecules, attracted widespread attention. The main advantage of this structure is designed to improve reaction selectivity and efficiency by accumulating reactants and catalysts within the chambers, thus increasing the frequency of collisions between reactants. Herein, the recent progress in the synthesis of spatially confined nanoreactors and their biological applications is summarized, covering various kinds of nanoreactors, including porous inorganic materials, porous crystalline materials with organic components and self-assembled polymers to construct nanoreactors. These design principles underscore how precise reaction control could be achieved by adjusting the structure and composition of the nanoreactors to create spatial confined. Furthermore, various applications of spatially confined nanoreactors are demonstrated in the biological fields, such as biocatalysis, molecular detection, drug delivery, and cancer therapy. These applications showcase the potential prospects of spatially confined nanoreactors, offering robust guidance for future research and innovation.

Impact of Nonionic Surfactants on Reactions of IREDs. Applications to Tandem Chemoenzymatic Sequences in Water

The influence of added surfactant to aqueous reaction mixtures containing various IREDs has been determined. Just the presence of a nonionic surfactant tends to increase both rates and extent of conversion to the targeted amines. The latter can be as much as >40% relative to buffer alone. Several tandem sequences featuring several steps that combine use of an IRED together with various types of chemocatalysis are also presented, highlighting the opportunities for utilizing chemoenzymatic catalysis, all in water.

Enantioselective merged gold/organocatalysis

Gold complexes, because of their unique carbophilic nature, have evolved as efficient catalysts for catalyzing various functionalization reactions of C-C multiple bonds. However, the realization of enantioselective transformations via gold catalysis remains challenging due to the geometrical constraints and coordination behaviors of gold complexes. In this context, merged gold/organocatalysis has emerged as one of the intriguing strategies to achieve enantioselective transformations which could not be possible by using a single catalytic system. Historically, in 2009, this field started with the merging of gold with axially chiral Brønsted acids and chiral amines to achieve enantioselective transformations. Since then, based on the unique reactivity profiles offered by each catalyst, several reports utilizing gold in conjunction with various chiral organocatalysts such as amines, Brønsted acids, N-heterocyclic carbenes, hydrogen-bonding and phosphine catalysts have been documented in the literature. This article demonstrates an up-to-date development in this field, especially focusing on the mechanistic interplay of gold catalysts with chiral organocatalysts.

The emerging chemistry of self-electrified water interfaces

Water is known for dissipating electrostatic charges, but it is also a universal agent of matter electrification, creating charged domains in any material contacting or containing it. This new role of water was discovered during the current century. It is proven in a fast-growing number of publications reporting direct experimental measurements of excess charge and electric potential. It is indirectly verified by its success in explaining surprising phenomena in chemical synthesis, electric power generation, metastability, and phase transition kinetics. Additionally, electrification by water is opening the way for developing green technologies that are fully compatible with the environment and have great potential to contribute to sustainability. Electrification by water shows that polyphasic matter is a charge mosaic, converging with the Maxwell-Wagner-Sillars effect, which was discovered one century ago but is still often ignored. Electrified sites in a real system are niches showing various local electrochemical potentials for the charged species. Thus, the electrified mosaics display variable chemical reactivity and mass transfer patterns. Water contributes to interfacial electrification from its singular structural, electric, mixing, adsorption, and absorption properties. A long list of previously unexpected consequences of interfacial electrification includes: "on-water" reactions of chemicals dispersed in water that defy current chemical wisdom; reactions in electrified water microdroplets that do not occur in bulk water, transforming the droplets in microreactors; and lowered surface tension of water, modifying wetting, spreading, adhesion, cohesion, and other properties of matter. Asymmetric capacitors charged by moisture and water are now promising alternative equipment for simultaneously producing electric power and green hydrogen, requiring only ambient thermal energy. Changing surface tension by interfacial electrification also modifies phase-change kinetics, eliminating metastability that is the root of catastrophic electric discharges and destructive explosions. It also changes crystal habits, producing needles and dendrites that shorten battery life. These recent findings derive from a single factor, water's ability to electrify matter, touching on the most relevant aspects of chemistry. They create tremendous scientific opportunities to understand the matter better, and a new chemistry based on electrified interfaces is now emerging.

Aqueous Micelles as Solvent, Ligand, and Reaction Promoter in Catalysis

Water is considered to be the most sustainable and safest solvent. Micellar catalysis is a significant contributor to the chemistry in water. It promotes pathways involving water-sensitive intermediates and transient catalytic species under micelles' shielding effect while also replacing costly ligands and dipolar-aprotic solvents. However, there is a lack of critical information about micellar catalysis. This includes why it works better than traditional catalysis in organic solvents, why specific rules in micellar catalysis differ from those of conventional catalysis, and how the limitations of micellar catalysis can be addressed in the future. This Perspective aims to highlight the current gaps in our understanding of micellar catalysis and provide an analysis of designer surfactants' origin and essential components. This will also provide a fundamental understanding of micellar catalysis, including how aqueous micelles can simultaneously perform multiple functions such as solvent, ligand, and reaction promoter.

Molecular Dynamic Simulations of Aqueous Micellar Organometallic Catalysis: Methane Functionalization as a Case Study

Molecular Dynamics (MD) simulations constitute a powerful tool that provides a 3D perspective of the dynamical behavior of chemical systems. Herein the first MD study of the dynamics of a catalytic organometallic system, in micellar media, is presented. The challenging methane catalytic functionalization into ethyl propionate through a silver-catalyzed process has been targeted as the case study. The intimate nature of the micelles formed with the surfactants sodium dodecylsulfate (SDS) and potassium perfluorooctane sulfonate (PFOS) has been ascertained, as well as the relative distribution of the main actors in this transformation, namely methane, the diazo reagent and the silver catalyst, the latter in two different forms: the initial compound and a silver-carbene intermediate. Catalyst deactivation occurs with halide containing surfactants dodecyltrimethylammonium chloride (DTAC) and Triton X-100. Computed simulations allow explaining the experimental results, indicating that micelles behave differently regarding the degree of accumulation and the local distribution of the reactants and their effect in the molecular collisions leading to net reaction.

Challenging cross couplings, in water, aided by in situ iodination of (hetero)aromatic bromides

Palladium-catalyzed reactions that involve functionalized substrates are oftentimes problematic. Those involving aryl or heteroaryl bromides that are either resistant to, or inefficient in such couplings present challenges that are difficult to overcome and may require development of an entirely new route, or worse, no opportunity to install the desired group using a standard coupling strategy. In this report, we describe a solution that allows for the in situ conversion of such bromo educts to transient iodide derivatives that can be made and used under environmentally responsible conditions, for subsequent reactions to highly functionalized, complex targets.

Decoupling of the Confused Complex in Oxidation of 3,3',5,5'-Tetramethylbenzidine for the Reliable Chromogenic Bioassay

Regulation of the reaction pathways is a perennial theme in the field of chemistry. As a typical chromogenic substrate, 3,3',5,5'-tetramethylbenzidine (TMB) generally undertakes one-electron oxidation, but the product (TMBox1) is essentially a confused complex and is unstable, which significantly hampers the clinic chromogenic bioassays for more than 50 years. Herein, we report that sodium dodecyl sulfate (SDS)-based micelles could drive the direct two-electron oxidation of TMB to the final stable TMBox2. Rather than activation of H2O2 oxidant in the one-electron TMB oxidation by common natural peroxidase, activation of the TMB substrate by SDS micelles decoupled the thermodynamically favorable complex between TMBox2 with unreacted TMB, leading to an unusual direct two-electron oxidation pathway. Mechanism studies demonstrated that the complementary spatial and electrostatic isolation effects, caused by the confined hydrophobic cavities and negatively charged outer surfaces of SDS micelles, were crucial. Further cascading with glucose oxidase, as a proof-of-concept application, allowed glucose to be more reliably measured, even in a broader range of concentrations without any conventional strong acid termination.

Genetically Encoded Oligomerization for Protein-Based Lighting Devices

Implementing proteins in optoelectronics represents a fresh idea toward a sustainable new class of materials with bio-functions that can replace environmentally unfriendly and/or toxic components without losing device performance. However, their native activity (fluorescence, catalysis, and so on) is easily lost under device fabrication/operation as non-native environments (organic solvents, organic/inorganic interfaces, and so on) and severe stress (temperature, irradiation, and so on) are involved. Herein, a gift bow genetically-encoded macro-oligomerization strategy is showcased to promote protein-protein solid interaction enabling i) high versatility with arbitrary proteins, ii) straightforward electrostatic driven control of the macro-oligomer size by ionic strength, and iii) stabilities over months in pure organic solvents and stress scenarios, allowing to integrate them into classical water-free polymer-based materials/components for optoelectronics. Indeed, rainbow-/white-emitting protein-based light-emitting diodes are fabricated, attesting a first-class performance compared to those with their respective native proteins: significantly enhanced device stabilities from a few minutes up to 100 h keeping device efficiency at high power driving conditions. Thus, the oligomerization concept is a solid bridge between biological systems and materials/components to meet expectations in bio-optoelectronics, in general, and lighting schemes, in particular.

DNA Nanomachine-Driven Heterogeneous Quadratic Amplification for Sensitive and Programmable miRNA Profiling

Inspired by the molecular crowding effect in biological systems, a novel heterogeneous quadratic amplification molecular circuit (HEQAC) was developed for sensitive bimodal miRNA profiling (HEQAC-BMP) by combining an MNAzyme-based DNA nanomachine with an entropy-driven catalytic hairpin assembly (E-CHA) autocatalytic circuit. Utilizing ferromagnetic nanomaterials as the substrate for DNA nanomachines, a biomimetic heterogeneous interface was established; thus, a localized molecular crowding system was created that can elevate the local reaction concentration and accelerate the molecular recognition process for a significant threshold signal. Simultaneously, the threshold signal undergoes further amplification by E-CHA and is transformed into a chemical signal, enabling a colorimetric-fluorescence bimodal signal readout. The HEQAC-BMP enables miRNA detection from 10 aM to 10 nM with detection limits of 3.7 aM (colorimetry) and 4.8 aM (fluorometry), respectively. Moreover, the design principle and strategy of HEQAC-BMP can be customized to address other critical viruses or diseases with life-threatening and socioeconomic impacts, enhancing healthcare outcomes for individuals.

Transition Metal Catalysis in Living Cells: Progress, Challenges, and Novel Supramolecular Solutions

The importance of transition metal catalysis is exemplified by its wide range of applications, for example in the synthesis of chemicals, natural products, and pharmaceuticals. However, one relatively new application is for carrying out new-to-nature reactions inside living cells. The complex environment of a living cell is not welcoming to transition metal catalysts, as a diverse range of biological components have the potential to inhibit or deactivate the catalyst. Here we review the current progress in the field of transition metal catalysis, and evaluation of catalysis efficiency in living cells and under biological (relevant) conditions. Catalyst poisoning is a ubiquitous problem in this field, and we propose that future research into the development of physical and kinetic protection strategies may provide a route to improve the reactivity of catalysts in cells.

Polymeric architecture as a tool for controlling the reactivity of palladium(II) loaded nanoreactors

Self-assembled systems, like polymeric micelles, have become great facilitators for conducting organic reactions in aqueous media due to their broad potential applications in green chemistry and biomedical applications. Massive strides have been taken to improve the reaction scope of such systems, enabling them to perform bioorthogonal reactions for prodrug therapy. Considering these significant advancements, we sought to study the relationships between the architecture of the amphiphiles and the reactivity of their PdII loaded micellar nanoreactors in conducting depropargylation reactions. Towards this goal, we designed and synthesized a series of isomeric polyethylene glycol (PEG)-dendron amphiphiles with different dendritic architectures but with an identical degree of hydrophobicity and hydrophilic to lipophilic balance (HLB). We observed that the dendritic architecture, which serves as the main binding site for the PdII ions, has greater influence on the reactivity than the hydrophobicity of the dendron. These trends remained constant for two different propargyl caged substrates, validating the obtained results. Density functional theory (DFT) calculations of simplified models of the dendritic blocks revealed the different binding modes of the various dendritic architectures to PdII ions, which could explain the observed differences in the reactivity of the nanoreactors with different dendritic architectures. Our results demonstrate how tuning the internal architecture of the amphiphiles by changing the orientation of the chelating moieties can be used as a tool for controlling the reactivity of PdII loaded nanoreactors.

Bottom-Up Synthesis of Multicompartmentalized Microreactors for Continuous Flow Catalysis

The bottom-up assembly of biomimetic multicompartmentalized microreactors for use in continuous flow catalysis remains a grand challenge because of the structural instability or the absence of liquid microenvironments to host biocatalysts in the existing systems. Here, we address this challenge using a strategy that combines stepwise Pickering emulsification with interface-confined cross-linking. Our strategy allows for the fabrication of robust multicompartmentalized liquid-containing microreactors (MLMs), whose interior architectures can be exquisitely tuned in a bottom-up fashion. With this strategy, enzymes and metal catalysts can be separately confined in distinct subcompartments of MLMs for processing biocatalysis or chemo-enzymatic cascade reactions. As exemplified by the enzyme-catalyzed kinetic resolution of racemic alcohols, our systems exhibit a durability of 2000 h with 99% enantioselectivity. Another Pd-enzyme-cocatalyzed dynamic kinetic resolution of amines further demonstrates the versatility and long-term operational stability of our MLMs in continuous flow cascade catalysis. This study opens up a new way to design efficient biomimetic multicompartmental microreactors for practical applications.

A micelle-mediated approach enables facile access to bridged oxabicyclo[n.3.1]alkene scaffolds

Oxabicyclo[n.3.1]alkene scaffolds present in a diverse range of complex natural products have been accessed by reacting 2-cycloalkenones with 1,3-cycloalkadiones in a micellar medium. This reaction occurring in a micellar confinement environment operates through a Michael addition/enolization/oxygen addition cascade to furnish highly functionalized constructs using a sustainable organic synthesis protocol. NMR analysis confirms that the locus of the solubilizates is within the palisade and stern regions of the micellar cavity.

Is Micellar Catalysis Green Chemistry?

Many years ago, twelve principles were defined for carrying out chemical reactions and processes from a green chemistry perspective. It is everyone's endeavor to take these points into account as far as possible when developing new processes or improving existing ones. Especially in the field of organic synthesis, a new area of research has thus been established: micellar catalysis. This review article addresses the question of whether micellar catalysis is green chemistry by applying the twelve principles to micellar reaction media. The review shows that many reactions can be transferred from an organic solvent to a micellar medium, but that the surfactant also has a crucial role as a solubilizer. Thus, the reactions can be carried out in a much more environmentally friendly manner and with less risk. Moreover, surfactants are being reformulated in their design, synthesis, and degradation to add extra advantages to micellar catalysis to match all the twelve principles of green chemistry.

Enantioselective Bioreduction of Medicinally Relevant Nitrogen-Heteroaromatic Ketones

We herein report an enantioselective bioreduction of ketones that bear the most frequently used nitrogen-heteroaromatics in FDA-approved drugs. Ten varieties of these nitrogen-containing heterocycles were systematically investigated. Eight categories were studied for the first time and seven types were tolerated, significantly expanding the substrate scope of plant-mediated reduction. By use of purple carrots in buffered aqueous media with a simplified reaction setup, this biocatalytic transformation was achieved within 48 h at ambient temperature, offering medicinal chemists a pragmatic and scalable tool to access a broad variety of nitrogen-heteroaryl-containing chiral alcohols. With multiple reactive sites, the structurally diverse set of chiral alcohols can be used for library compound preparation, early route-scouting activities, and synthesis of other pharmaceutical molecules, favorably accelerating medicinal chemistry campaigns.

Surfactant Micellar and Vesicle Microenvironments and Structures under Synthetic Organic Conditions

Fluorescence lifetime imaging microscopy (FLIM) reveals vesicle sizes, structures, microenvironments, reagent partitioning, and system evolution with two chemical reactions for widely used surfactant-water systems under conditions relevant to organic synthesis, including during steps of Negishi cross-coupling reactions. In contrast to previous investigations, the present experiments characterize surfactant systems with representative organohalide substrates at high concentrations (0.5 M) that are reflective of the preparative-scale organic reactions performed and reported in water. In the presence of representative organic substrates, 2-iodoethylbenzene and 2-bromo-6-methoxypyridine, micelles swell into emulsion droplets that are up to 20 μm in diameter, which is 3-4 orders of magnitude larger than previously measured in the absence of an organic substrate (5-200 nm). The partitioning of reagents in these systems is imaged through FLIM─demonstrated here with nonpolar, amphiphilic, organic, basic, and oxidative-addition reactive compounds, a reactive zinc metal powder, and a palladium catalyst. FLIM characterizes the chemical species and/or provides microenvironment information inside micelles and vesicles. These data show that surfactants cause surfactant-dictated microenvironments inside smaller micelles (<200 nm) but that addition of a representative organic substrate produces internal microenvironments dictated primarily by the substrate rather than by the surfactant, concurrent with swelling. Addition of a palladium catalyst causes the internal environments to differ between vesicles─information that is not available through nor predicted from prior analytical techniques. Together, these data provide immediately actionable information for revising reaction models of surfactant-water systems that underpin the development of sustainable organic chemistry in water.

Integration of chemo- and bio-catalysis to intensify bioprocesses

Nature has evolved highly efficient and complex systems to perform cascade reactions by the elegant combination of desired enzymes, offering a strategy for achieving efficient bioprocess intensification. Chemoenzymatic cascade reactions (CECRs) merge the complementary strengths of chemo-catalysis and bio-catalysis, such as the wide reactivity of chemo-catalysts and the exquisite selective properties of biocatalysts, representing an important step toward emulating nature to construct artificial systems for achieving bioprocess intensification. However, the incompatibilities between the two catalytic disciplines make CECRs highly challenging. In recent years, great advances have been made to develop strategies for constructing CECRs. In this regard, this chapter introduces the general concepts and representative strategies, including temporal compartmentalization, spatial compartmentalization and chemo-bio nanoreactors. Particularly, we focus on what platform methods and technologies can be used, and how to implement these strategies. The future challenges and strategies in this burgeoning research area are also discussed.

Simplified Preparation of ppm Pd-Containing Nanoparticles as Catalysts for Chemistry in Water

A protocol has been developed that not only simplifies the preparation of nanoparticles (NPs) containing ppm levels of ligated palladium that affect heterogeneous catalysis but also ensures that they afford products of cross-couplings reproducibly due to the freshly prepared nature of each reagent. Four different types of couplings are studied: Suzuki-Miyaura, Sonogashira, Mizoroki-Heck, and Negishi reactions, all performed under mild aqueous micellar conditions. The simplified process relies on the initial formation of stable, storable Pd- and ligand-free NPs, to which is then added the appropriate amount of Pd(OAc)₂ and ligand-matched to the desired type of coupling, in water.

Introducing Savie: A Biodegradable Surfactant Enabling Chemo- and Biocatalysis and Related Reactions in Recyclable Water

Savie is a biodegradable surfactant derived from vitamin E and polysarcosine (PSar) developed for use in organic synthesis in recyclable water. This includes homogeneous catalysis (including examples employing only ppm levels of catalyst), heterogeneous catalysis, and biocatalytic transformations, including a multistep chemoenzymatic sequence. Use of Savie frequently leads to significantly higher yields than do conventional surfactants, while obviating the need for waste-generating organic solvents.

Effective Production of Selected Dioxolanes by Sequential Bio- and Chemocatalysis Enabled by Adapted Solvent Switching

Most combinations of chemo- and biocatalysis take place in aqueous media or require a solvent change with complex intermediate processing. Using enzymes in the same organic solvent as the chemocatalyst eliminates this need. Here, it was shown that a complete chemoenzymatic cascade to form dioxolanes could be carried out in a purely organic environment. The result, including downstream processing, was compared with a classical mode, shifting solvent. First, a two-step enzyme cascade starting from aliphatic aldehydes to chiral diols (3,4-hexanediol and 4,5-octanediol) was run either in an aqueous buffer or in the potentially biobased solvent cyclopentyl methyl ether. Subsequently, a ruthenium molecular catalyst enabled the conversion to dioxolanes [e. g., (4S,5S)-dipropyl-1,3-dioxolane]. Importantly, the total synthesis of this product was not only highly stereoselective but also based on the combination of biomass, CO₂ , and hydrogen, thus providing an important example of a bio-hybrid chemical.

Expanding the Synthetic Toolbox through Metal-Enzyme Cascade Reactions

The combination of metal-, photo-, enzyme-, and/or organocatalysis provides multiple synthetic solutions, especially when the creation of chiral centers is involved. Historically, enzymes and transition metal species have been exploited simultaneously through dynamic kinetic resolutions of racemates. However, more recently, linear cascades have appeared as elegant solutions for the preparation of valuable organic molecules combining multiple bioprocesses and metal-catalyzed transformations. Many advantages are derived from this symbiosis, although there are still bottlenecks to be addressed including the successful coexistence of both catalyst types, the need for compatible reaction media and mild conditions, or the minimization of cross-reactivities. Therefore, solutions are here also provided by means of catalyst coimmobilization, compartmentalization strategies, flow chemistry, etc. A comprehensive review is presented focusing on the period 2015 to early 2022, which has been divided into two main sections that comprise first the use of metals and enzymes as independent catalysts but working in an orchestral or sequential manner, and later their application as bionanohybrid materials through their coimmobilization in adequate supports. Each part has been classified into different subheadings, the first part based on the reaction catalyzed by the metal catalyst, while the development of nonasymmetric or stereoselective processes was considered for the bionanohybrid section.

Where Chemocatalysis Meets Biocatalysis: In Water

Chemoenzymatic catalysis, by definition, involves the merging of sequential reactions using both chemocatalysis and biocatalysis, typically in a single reaction vessel. A major challenge, the solution to which, however, is associated with numerous advantages, is to run such one-pot processes in water: the majority of enzyme-catalyzed processes take place in water as Nature's reaction medium, thus enabling a broad synthetic diversity when using water due to the option to use virtually all types of enzymes. Furthermore, water is cheap, abundantly available, and environmentally friendly, thus making it, in principle, an ideal reaction medium. On the other hand, most chemocatalysis is routinely performed today in organic solvents (which might deactivate enzymes), thus appearing to make it difficult to combine such reactions with biocatalysis toward one-pot cascades in water. Several creative approaches and solutions that enable such combinations of chemo- and biocatalysis in water to be realized and applied to synthetic problems are presented herein, reflecting the state-of-the-art in this blossoming field. Coverage has been sectioned into three parts, after introductory remarks: (1) Chapter 2 focuses on historical developments that initiated this area of research; (2) Chapter 3 describes key developments post-initial discoveries that have advanced this field; and (3) Chapter 4 highlights the latest achievements that provide attractive solutions to the main question of compatibility between biocatalysis (used predominantly in aqueous media) and chemocatalysis (that remains predominantly performed in organic solvents), both Chapters covering mainly literature from ca. 2018 to the present. Chapters 5 and 6 provide a brief overview as to where the field stands, the challenges that lie ahead, and ultimately, the prognosis looking toward the future of chemoenzymatic catalysis in organic synthesis.

Coupling photocatalytic water oxidation with reductive transformations of organic molecules

The utilization of readily available and non-toxic water by photocatalytic water splitting is highly attractive in green chemistry. Herein we report that light-induced oxidative half-reaction of water splitting is effectively coupled with reduction of organic compounds, which provides a light-induced avenue to use water as an electron donor to enable reductive transformations of organic substances. The present strategy allows various aryl bromides to undergo smoothly the reductive coupling with Pd/g-C₃N₄* as the photocatalyst, giving a pollutive reductant-free method for synthesizing biaryl skeletons. Moreover, the use of green visible-light energy endows this process with more advantages including mild conditions and good functional group tolerance. Although this method has some disadvantages such as a use of environmentally unfriendly 1,2-dioxane, an addition of Na₂CO₃ and so on, it can guide chemists to use water as a reducing agent to develop clean procedures for various organic reactions.

While reductive coupling strategies in organic synthesis are crucial, most require additional sacrificial or toxic reagents. Here, authors demonstrate water as mild reducing agent in the photochemical reduction of organic compounds paired with photocatalytic water oxidation.

Dissipative self-assembly of a proline catalyst for temporal regulation of the aldol reaction

The spatiotemporal regulation of chemical reactivity in biological systems permits a network of metabolic reactions to take place within the same cellular environment. The exquisite control of reactivity is often mediated by out-of-equilibrium structures that remain functional only as long as fuel is present to maintain the higher energy, active state. An important goal in supramolecular chemistry aims to develop functional, energy dissipating systems that approach the sophistication of biological machinery. The challenge is to create strategies that couple the energy consumption needed to promote a molecule to a higher energy, assembled state to a functional property such as catalytic activity. In this work, we demonstrated that the assembly of a spiropyran (SP) dipeptide (1) transiently promoted the proline-catalyzed aldol reaction in water when visible light was present as fuel. The transient catalytic activity emerged from 1 under light illumination due to the photoisomerization of the monomeric, O-protonated (1-MCH⁺) merocyanine form to the spiropyran (1-SP) state, which rapidly assembled into nanosheets capable of catalyzing the aldol reaction in water. When the light source was removed, thermal isomerization to the more stable MCH⁺ form caused the nanosheets to dissociate into a catalytically inactive, monomeric state. Under these conditions, the aldol reaction could be repeatedly activated and deactivated by switching the light source on and off.

Cascade Processes with Micellar Reaction Media: Recent Advances and Future Directions

Reducing the use of solvents is an important aim of green chemistry. Using micelles self-assembled from amphiphilic molecules dispersed in water (considered a green solvent) has facilitated reactions of organic compounds. When performing reactions in micelles, the hydrophobic effect can considerably accelerate apparent reaction rates, as well as enhance selectivity. Here, we review micellar reaction media and their potential role in sustainable chemical production. The focus of this review is applications of engineered amphiphilic systems for reactions (surface-active ionic liquids, designer surfactants, and block copolymers) as reaction media. Micelles are a versatile platform for performing a large array of organic chemistries using water as the bulk solvent. Building on this foundation, synthetic sequences combining several reaction steps in one pot have been developed. Telescoping multiple reactions can reduce solvent waste by limiting the volume of solvents, as well as eliminating purification processes. Thus, in particular, we review recent advances in “one-pot” multistep reactions achieved using micellar reaction media with potential applications in medicinal chemistry and agrochemistry. Photocatalyzed reactions in micellar reaction media are also discussed. In addition to the use of micelles, we emphasize the process (steps to isolate the product and reuse the catalyst).

Chemo-Biocascade Reactions Enabled by Metal–Organic Framework Micro-Nanoreactor

The one-pot combination of biocatalytic and chemocatalytic reactions represents an economically and ecologically attractive concept in the emerging cascade processes for manufacturing. The mutual incompatibility of biocatalysis and chemocatalysis, however, usually causes the deactivation of catalysts, the mismatching of reaction dynamic, and further challenges their integration into concurrent chemo-biocascades. Herein, we have developed a convenient strategy to construct versatile functional metal–organic framework micro-nanoreactors (MOF–MNRs), which can realize not only the encapsulation and protection of biocatalysts but also the controllable transmission of substances and the mutual communication of the incompatible chemo-biosystems. Importantly, the MOFs serving as the shell of MNRs have the capability of enriching the chemocatalysts on the surface and improving the activity of the chemocatalysts to sufficiently match the optimum aqueous reaction system of biocatalysts, which greatly increase the efficiency in the combined concurrent chemo-biocatalysis. Such strategy of constructing MOF–MNRs provides a unique platform for connecting the “two worlds” of chemocatalysis and biocatalysis.

Coupling metal and whole-cell catalysis to synthesize chiral alcohols

BACKGROUND

The combination of metal-catalyzed reactions and enzyme catalysis has been an essential tool for synthesizing chiral pharmaceutical intermediates in the field of drug synthesis. Metal catalysis commonly enables the highly efficient synthesis of molecular scaffolds under harsh organic conditions, whereas enzymes usually catalyze reactions in mild aqueous medium to obtain high selectivity. Since the incompatibility between metal and enzyme catalysis, there are limitations on the compatibility of reaction conditions that must be overcome.

FINDINGS

We report a chemoenzymatic cascade reaction involved Palladium (Pd) catalyzed Suzuki-Miyaura coupling and whole-cell catalyzed C = O asymmetric reduction for enantioselective synthesis of value-added chiral alcohol. The cell membrane serves as a natural barrier can protect intracellular enzymes from organic solvents.

CONCLUSIONS

With dual advantages of cascade catalysis and biocompatibility, our work provides a rational strategy to harvest chiral alcohols in high yield and excellent enantioselectivity, as a channel to establish chemoenzymatic catalysis.

Micelle-guided Morita-Baylis-Hillman reaction of ketones in water

A novel Morita-Baylis-Hillman reaction employing electron-deficient alkenes like acrylonitrile with a wide range of aryl and aliphatic ketones using cooperative catalysis in micellar media has been delineated. This transformation executed in water under mild reaction conditions in a confined environment of micelles is aligned to the ideas of sustainable and green chemistry. The site of the reaction was established by incisive proton NMR studies in the palisade region of the micellar assembly. This study is expected to encourage the use of micellar catalysis for energetically less favorable chemical reactions.