Synthetic Applications Research Articles

Palladium-Catalyzed Ortho-Alkylation of Iodoarenes Enabled by a Cooperative Cycloolefin Ligand and a Bulky Trialkylphosphine

We recently achieved ortho-alkylation of iodoarenes utilizing a dual-ligand catalytic system that effectively combines palladium/olefin ligand cooperative catalysis with reversible C(sp²)−I reductive elimination enabled by a bulky trialkylphosphine ligand. Through careful mechanistic investigations, we confirmed the compatibility of the crucial steps involved in this process by isolating key organometallic intermediates and studying their stoichiometry transformations. Utilizing this protocol, we successfully achieved the ortho-alkylation of a variety of iodoarene substrates, thereby expanding the scope of applications for Catellani-type reactions. This study showcases the synthetic potential of the Pd/olefin ligand cooperative system as an innovative complement to established Pd/NBE catalysis. In this Synpacts article, we present the conceptual framework underpinning this reaction and detail the key aspects of its development. 1Introduction 2Research Background 2.1The Catellani Reaction: Pd/Norbornene Catalysis 2.2Cooperative Cycloolefin Ligands for the Catellani-Type Reactions 2.3C-X Reductive Elimination on Pd Center 3Development of the Reaction 3.1Proof-of-Concept by Stoichiometric Reactions 3.2Substrate Scope and Synthetic Applications 4Conclusion

Photoredox catalysis of acridinium and quinolinium ion derivatives

AbstractPhotoredox catalysis has attracted increasing attention because of wide range of synthetic transformations and solar energy conversion applications. Reviews on photoredox catalysis have so far focused predominantly on the synthetic applications. This review highlights how organic photoredox catalysts were developed and how they function as efficient photocatalysts in mechanistic point of views. In particular, 9‐mesityl‐10‐methylactidinium (Acr+–Mes) has been highlighted as one of the best organic photoredox catalysts. Acr+–Mes was originally developed as a model compound of the photosynthetic reaction center to mimic the long lifetime of the charge‐separated state in which the energy is converted to chemical energy in photosynthesis. The reason why Acr+–Mes acts as one of the most efficient photoredox catalyst is clarified in terms of the one‐electron redox potentials and long lifetimes of the electron‐transfer state (Acr•–Mes•+) produced upon photoexcitation of Acr+–Mes in different solvents. The reason why the mesityl substituent at the 9‐position of the Acr+ moiety is essential for the efficient photoredox catalysis is discussed in comparison with acridinium ions with different substituents R (Acr+–R) including 10‐methylacridinium ion with no substituent (AcrH+). The mechanisms of photoredox catalysis of Acr+–Mes are discussed in various synthetic transformations and solar energy conversion reactions mimicking photosynthesis. Photoredox catalysis of quinolinium ion and its derivatives is also discussed in comparison with that of Acr+–Mes. Finally, immobilization of Acr+–Mes and quinolinium ions to form the composite catalysts with redox catalyst is discussed to improve the photoredox catalytic activity and stability.

Cationic Ring-Opening Polymerization-Induced Self-Assembly (CROPISA) of 2-Oxazolines: From Block Copolymers to One-Step Gradient Copolymer Nanoparticles.

In recent years, polymerization-induced self-assembly (PISA) has emerged as a powerful method for the straightforward synthesis of polymer nanoparticles at high concentration. In this study, we describe for the first time the synthesis of poly(2-oxazoline) nanoparticles by dispersion cationic ring-opening polymerization-induced self-assembly (CROPISA) in n-dodecane. Specifically, a n-dodecane-soluble aliphatic poly(2-(3-ethylheptyl)-2-oxazoline) (PEHOx) block was chain-extended with poly(2-phenyl-2-oxazoline) (PPhOx). While the PhOx monomer is soluble in n-dodecane, its polymerization leads to n-dodecane-insoluble PPhOx, which leads to in situ self-assembly of the formed PEHOx-b-PPhOx copolymers. The polymerization kinetics and micellization upon second block formation were studied, and diverse nanoparticle dispersions were prepared, featuring varying block lengths and polymer concentrations, leading to dispersions with distinctive morphologies and physical properties. Finally, we developed a single-step protocol for the synthesis of polymer nanoparticles directly from monomers via gradient copolymerization CROPISA, which exploits the significantly greater reactivity of EHOx compared to that of PhOx during the statistical copolymerization of both monomers. Notably, this approach provides access to formulations with monomer compositions otherwise unattainable through the block copolymerization method. Given the synthetic versatility and application potential of poly(2-oxazolines), the developed CROPISA method can pave the way for advanced nanomaterials with favorable properties as demonstrated by using the obtained nanoparticles for stabilization of Pickering emulsions.

Cationic Ring‐Opening Polymerization‐Induced Self‐Assembly (CROPISA) of 2‐Oxazolines: From Block Copolymers to One‐Step Gradient Copolymer Nanoparticles

AbstractIn recent years, polymerization‐induced self‐assembly (PISA) has emerged as a powerful method for the straightforward synthesis of polymer nanoparticles at high concentration. In this study, we describe for the first time the synthesis of poly(2‐oxazoline) nanoparticles by dispersion cationic ring‐opening polymerization‐induced self‐assembly (CROPISA) in n‐dodecane. Specifically, a n‐dodecane‐soluble aliphatic poly(2‐(3‐ethylheptyl)‐2‐oxazoline) (PEHOx) block was chain‐extended with poly(2‐phenyl‐2‐oxazoline) (PPhOx). While the PhOx monomer is soluble in n‐dodecane, its polymerization leads to n‐dodecane‐insoluble PPhOx, which leads to in situ self‐assembly of the formed PEHOx‐b‐PPhOx copolymers. The polymerization kinetics and micellization upon second block formation were studied, and diverse nanoparticle dispersions were prepared, featuring varying block lengths and polymer concentrations, leading to dispersions with distinctive morphologies and physical properties. Finally, we developed a single‐step protocol for the synthesis of polymer nanoparticles directly from monomers via gradient copolymerization CROPISA, which exploits the significantly greater reactivity of EHOx compared to that of PhOx during the statistical copolymerization of both monomers. Notably, this approach provides access to formulations with monomer compositions otherwise unattainable through the block copolymerization method. Given the synthetic versatility and application potential of poly(2‐oxazolines), the developed CROPISA method can pave the way for advanced nanomaterials with favorable properties as demonstrated by using the obtained nanoparticles for stabilization of Pickering emulsions.

Nickel‐catalyzed Reductive Hydrolysis of Nitriles to Alcohols

Nitriles are an abundant class of compounds that are widely used as versatile feedstocks to produce various chemicals including pharmaceuticals, and agrochemicals as well as materials. Here we report Ni‐catalyzed reductive hydrolysis of nitriles to alcohols in the presence of molecular hydrogen. This conversion likely occurs in a domino reaction sequence that first involves the hydrogenation of nitrile to primary imine, then the hydrolysis of imine, and subsequent deamination to the aldehyde, which is finally hydrogenated to the desired alcohol. Crucial for this reductive hydrolysis process is the commercially available triphos‐ligated Ni‐complex that enables highly efficient and selective transformation of aromatic, heterocyclic, and aliphatic nitriles including fatty nitriles to prepare functionalized primary alcohols. Further, the synthetic applicability of this Ni‐based protocol is presented for the selective conversion of nitrile to alcoholic group in structurally diverse and complex drug molecules as well as agrochemicals. The resulting products, alcohols are indispensable chemicals commonly used in organic synthesis and life sciences as well as material and energy technologies.

A General Pd-Catalyzed C2-H Arylation of Benzoxazoles with Highly Sterically Congested Aryl Chlorides Enabled by a Fittingly Tuned Ligand.

The benzoxazole core, featuring a sterically congested 2,6-disubstituted aryl fragment at the C2 position, exhibits exclusive three-dimensional structures that are essential for particular applications in material science and pharmaceutical development. Despite their importance, the synthesis of these compounds has posed challenges with an efficient preparation strategy still lacking. In this study, we introduced a new indolylphosphine ligand, PCy2-Man-phos, specifically designed to facilitate the C2-H arylation of benzoxazoles with sterically hindered aryl chlorides in general. The excellent functional group compatibility and rich arene substituted pattern enable the creation of highly decorated and sterically demanding 2-arylbenzoxazole frameworks, showing significant potential for diverse synthetic applications.

Nickel-catalyzed Reductive Hydrolysis of Nitriles to Alcohols.

Nitriles are an abundant class of compounds that are widely used as versatile feedstocks to produce various chemicals including pharmaceuticals, and agrochemicals as well as materials. Here we report Ni-catalyzed reductive hydrolysis of nitriles to alcohols in the presence of molecular hydrogen. This conversion likely occurs in a domino reaction sequence that first involves the hydrogenation of nitrile to primary imine, then the hydrolysis of imine, and subsequent deamination to the aldehyde, which is finally hydrogenated to the desired alcohol. Crucial for this reductive hydrolysis process is the commercially available triphos-ligated Ni-complex that enables highly efficient and selective transformation of aromatic, heterocyclic, and aliphatic nitriles including fatty nitriles to prepare functionalized primary alcohols. Further, the synthetic applicability of this Ni-based protocol is presented for the selective conversion of nitrile to alcoholic group in structurally diverse and complex drug molecules as well as agrochemicals. The resulting products, alcohols are indispensable chemicals commonly used in organic synthesis and life sciences as well as material and energy technologies.

Diversity-Oriented Synthesis of Spirooxindoles via Asymmetric Organocatalytic Regiodivergent Cascade Reactions.

A regiodivergent strategy for the asymmetric diversity-oriented synthesis of spirooxindoles via organocatalytic cascade reactions is developed. Two regioselective pathways can be precisely controlled with different aminocatalysts in the reaction of 2-hydroxycinnamaldehydes and β,β-disubstituted 3-alkylidene oxindoles. The cascade vinylogous Michael/oxa-Michael/aldol reactions gave spiro-bridged oxindoles bearing two adjacent quaternary stereocenters, while the cascade oxa-Michael/Michael reactions gave spirooxindoles. Moreover, during the synthetic application studies, an acid-catalyzed rearrangement of spiro-bridged oxindoles was found to yield biologically important 3-alkylidene oxindoles.

Copper‐Mediated C−H Functionalization of Amines, Imines, and Amides: Recent Developments and Synthetic Applications

AbstractCopper‐mediated C−H functionalization has emerged as a powerful strategy for the selective modification of nitrogen‐containing molecules, offering significant advancements in organic synthesis. This review provides a comprehensive overview of recent developments in copper‐catalyzed C−H functionalization reactions of amines, imines, and amides, from 2013 to present, emphasizing their synthetic applications and mechanistic insights. It also discusses the impact of these methodologies on the construction of complex molecular architectures, including pharmaceuticals and natural products. This review aims to provide valuable guidance for researchers seeking to leverage copper‐mediated strategies in their synthetic endeavors by creating current knowledge and identifying future directions. We have highlighted the new bonds formed through C−H functionalizations for the convenience of readers.

Methanol Activation: Strategies for Utilization of Methanol as C1 Building Block in Sustainable Organic Synthesis.

The development of efficient and sustainable chemical processes which use greener reagents and solvents, currently play an important role in current research. Methanol, a cheap and readily available resource from chemical industry, could be activated by transition metal catalysts. This review focuses in covering the recent five-years literature and provides a systematic summary of strategies for methanol activation and the use in organic chemistry. Based on these strategies, many new synthetic methods have been developed for methanol utilization as the C1 building block in methylation, hydromethylation, aminomethylation, formylation reactions, as well as the syntheses of urea derivatives and heterocycles. The achievements, synthetic applications, limitations, some advanced approaches, and future perspectives of the methanol activation methodologies have been described in this review.

Nickel-Catalyzed Decarboxylative Cross-Coupling of NHPI Esters to Access 1,4-Dialkylbenzenes.

A practical nickel-catalyzed decarboxylative cross-coupling of N-hydroxyphthalimide esters with 1,4-diiodobenzene analogues has been developed. Under mild reaction conditions, a series of structurally interesting 1,4-dialkylbenzene analogues have been accessed with good functional group tolerance, which are versatile precursors for organic synthesis and a kind of important unit for bioactive molecules, polymers, and other materials. The synthetic application of this methodology was demonstrated by the synthesis of 3-6-dialkylcarbazole derivatives.

Management of fall armyworm, Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) in maize (Zea mays L.) in Indonesia and Thailand via mating disruption

The fall armyworm, Spodoptera frugiperda (Smith), has been problematic in Southeast Asia since its invasion in 2019. Fall armyworm management in these areas largely depends on synthetic insecticide application, and alternative management practices are very few and impractical. The demand for new and more sustainable tools for managing this pest has increased. In this study, we tested the mating disruption (MD) efficacy of fall armyworm sex pheromone in low-density polyethylene dispensers containing 2.5 g of blended active ingredients, (Z)-9-tetradecen-1-yl acetate (Z9-14Ac) and (Z)-11-hexadecen-1-yl acetate (Z11-16Ac) in a ratio of 87:13. The primary objective was to evaluate the optimal density of the dispensers/ha and understand the benefits of MD in reducing the damage caused by fall armyworm and associated insecticide applications as compared to conventional growers’ practices in Indonesia and Thailand. Research was conducted at 16 locations across Indonesia and Thailand in 2020 and 2021 in 9-ha treatment plots and compared to conventional growers practice. Trap reduction, a measure of MD, was significantly higher (74–90%) with 30 dispensers/ha than with non-dispenser areas, suggesting high levels of mating suppression. MD’s primary benefit is damage reduction, where 30 dispensers/ha reduced damage caused by fall armyworm larvae by 34–35% while simultaneously enabling a greater than 50% reduction in insecticide usage compared to the conventional growers’ practice. Our results show the effectiveness and feasibility of MD using pheromones as an essential management tactic for fall armyworm. These results represent a potential step towards more efficacious and sustainable pest management in Southeast Asia.

Selective Synthesis of Vinyl Sulfides or 2-Methyl Benzothiazoles from Disulfides and CaC2 Mediated by a Trisulfur Radical Anion.

In this report, we have established a novel and efficient method for selectively synthesizing either vinyl sulfides or 2-methylbenzothiazoles from the reaction of CaC2 and disulfides. The selective synthesis of these two distinct products can be controlled by simply adjusting the amount of K2S. The underlying reaction mechanism has been thoroughly investigated through control experiments, HRMS, and FTIR, which collectively support the pivotal role of a trisulfur radical anion. This radical species, generated in situ from K2S, is essential for the homolytic cleavage of the S-S bonds in a catalytic manner. Additionally, the trisulfur radical anion also acts as an effective mediator for activating the vinyl group of 2-aminophenyl vinyl sulfides, facilitating the crucial intramolecular cyclization required to produce 2-methylbenzothiazoles. Moreover, CaC2 not only serves as an acetylene source but also creates the basic conditions essential for the selective formation of vinyl sulfides. This methodology demonstrates broad substrate compatibility and excellent functional group tolerance, significantly enhancing its practical utility in diverse synthetic applications.

Effect of Translation-Enhancing Nascent SKIK Peptide on the Arrest Peptides Containing Consecutive Proline.

Ribosome arrest peptides (RAPs) such as the SecM arrest peptide (SecM AP: FSTPVWISQAQGIRAGP) and WPPP with consecutive Pro residues are known to induce translational stalling in Escherichia coli. We demonstrate that the translation-enhancing SKIK peptide tag, which consists of four amino acid residues Ser-Lys-Ile-Lys, effectively alleviates translational arrest caused by WPPP. Moreover, the proximity between SKIK and WPPP significantly influences the extent of this alleviation, observed in both PURE cell-free protein synthesis and in vivo protein production systems, resulting in a substantial increase in the yield of proteins containing such RAPs. Furthermore, we unveil that nascent SKIK peptide tag and translation elongation factor P (EF-P) alleviate ribosome stalling in consecutive-Pro-rich protein to synergistically promote translation. A kinetic analysis based on the generation of superfolder green fluorescent protein under in vitro translation reaction reveals that the ribosome turnover is enhanced by more than 10-fold when the SKIK peptide tag is positioned immediately upstream of the SecM AP sequence. Our findings provide valuable insights into optimizing protein production processes, which are essential for advancing synthetic biology applications.

Unveiling the Mechanism of Deprotonation and Proton Transfer of DNA Polymerase Catalysis via Single-Molecule Conductance.

DNA polymerases (Pols) play important roles in the transmission of genetic information. Although the function and (de)regulation of Pols are linked to many human diseases, the key mechanism of 3'-OH deprotonation and the PPi formation are not totally clear. In this work, a method is presented to detect the full catalytic cycle of human Pol (hPol β) in graphene-molecule-graphene single-molecule junctions. Real-time in situ monitoring successfully revealed the spatial and temporal properties of the open and closed conformation states of hPol β, distinguishing the reaction states in the Pols catalytic cycle and unveiling 3'-OH deprotonation and pyrophosphate (PPi) formation mechanism of hPol β. Proton inventory experiment demonstrated that the rate-limiting step of PPi formation is deprotonation, which occurs before a reverse conformational change. Additionally, by detecting the acidity (pKa), it is found that MgA-bound OH- acted as a general base and activated the nucleophile of 3'-OH, and that acidic residue D190 or D192 coordinated with MgB as a proton donor to PPi. This work provides useful insights into a fundamental chemical reaction that impacts genome synthesis efficiency and Pol fidelity, which the discovery of Pol-targeting drugs and design of artificial Pols for DNA synthetic applications are expected to accelerated.

Red Light Responsive Cre Recombinase for Bacterial Optogenetics.

Optogenetic tools have been used in a wide range of microbial engineering applications that benefit from the tunable, spatiotemporal control that light affords. However, the majority of current optogenetic constructs for bacteria respond to blue light, limiting the potential for multichromatic control. In addition, other wavelengths offer potential benefits over blue light, including improved penetration of dense cultures and reduced potential for toxicity. In this study, we introduce OptoCre-REDMAP, a red light inducible Cre recombinase system in Escherichia coli. This system harnesses the plant photoreceptors PhyA and FHY1 and a split version of Cre recombinase to achieve precise control over gene expression and DNA excision. We optimized the design by modifying the start codon of Cre and characterized the impact of different levels of induction to find conditions that produced minimal basal expression in the dark and induced full activation within 4 h of red light exposure. We characterized the system's sensitivity to ambient light, red light intensity, and exposure time, finding OptoCre-REDMAP to be reliable and flexible across a range of conditions. In coculture experiments with OptoCre-REDMAP and the blue light responsive OptoCre-VVD, we found that the systems responded orthogonally to red and blue light inputs. Direct comparisons between red and blue light induction with OptoCre-REDMAP and OptoCre-VVD demonstrated the superior penetration properties of red light. OptoCre-REDMAP's robust and selective response to red light makes it suitable for advanced synthetic biology applications, particularly those requiring precise multichromatic control.

On the Halogenation of Tyrosine N‐Oxime Methyl Ester

Efficient syntheses of mono‐, di‐, and heterodihalogenated derivatives of tyrosine N‐oxime methyl ester are reported. Monohalogenation with N‐bromosuccinimide (NBS), N‐chlorosuccinimide (NCS) or N‐iodosuccinimide (NIS) was optimized by addition of acid to suppress dihalogenation, affording bromo, chloro, and iodo derivatives in 71%, 50‐53%, and 78‐80% yields, respectively. Homodihalogenation utilized a two‐step, one‐flask process via a spirocyclic intermediate, yielding dibromo, dichloro, and diiodo analogues, respectively (75‐76%, 54‐56%, 79‐80%). This strategy was extended to synthesize heterodihalogenated bromochloro, bromoiodo, and chloroiodo derivatives from monohalogenated analogues (50‐77%). Key to this approach was the formation of an oxidized spirocyclic intermediate using excess N‐halosuccinimide, followed by Na₂S₂O₄ reduction. This method ensures complete conversion and simplifies purification. Nine halogenated building blocks were prepared. These methods provide practical access to versatile precursors for natural product synthesis and derivatization, offering potential for diverse synthetic applications including regioselective palladium‐catalyzed couplings.

Catalytic Enantioselective Synthesis of Boron-Stereogenic and Axially Chiral BODIPYs via Rhodium(II)-Catalyzed C-H (Hetero) Arylation with Diazonaphthoquinones and Diazoindenines.

The molecular engineering of boron dipyrromethenes (BODIPYs) has garnered widespread attention due to their structural diversity enabling tailored physicochemical properties for optimal applications. However, catalytic enantioselective synthesis of structurally diverse boron-stereogenic BODIPYs through intermolecular desymmetrization and BODIPYs with atroposelectivity remains elusive. Here, we showcase rhodium(II)-catalyzed site-specific C-H (hetero)arylations of prochiral BODIPYs and polysubstituted BODIPYs with diazonaphthoquinonesand diazoindenines, providing efficient pathways for the rapid assembly of versatile (hetero)arylated boron-stereogenic and axially chiral BODIPYs through long-range desymmetrization and axial rotational restriction modes. The synthetic application of the procedures has been emphasized by the efficient synthesis of BODIPY derivatives with various functions. Photophysical properties, bioimaging, and lipid droplet-specific targeting capability of tailored BODIPYs are also demonstrated, indicating their promising applications in biomedical research, medicinal chemistry, and material science.

Catalytic Enantioselective Synthesis of Boron‐Stereogenic and Axially Chiral BODIPYs via Rhodium(II)‐Catalyzed C−H (Hetero) Arylation with Diazonaphthoquinones and Diazoindenines

AbstractThe molecular engineering of boron dipyrromethenes (BODIPYs) has garnered widespread attention due to their structural diversity enabling tailored physicochemical properties for optimal applications. However, catalytic enantioselective synthesis of structurally diverse boron‐stereogenic BODIPYs through intermolecular desymmetrization and BODIPYs with atroposelectivity remains elusive. Here, we showcase rhodium(II)‐catalyzed site‐specific C−H (hetero)arylations of prochiral BODIPYs and polysubstituted BODIPYs with diazonaphthoquinonesand diazoindenines, providing efficient pathways for the rapid assembly of versatile (hetero)arylated boron‐stereogenic and axially chiral BODIPYs through long‐range desymmetrization and axial rotational restriction modes. The synthetic application of the procedures has been emphasized by the efficient synthesis of BODIPY derivatives with various functions. Photophysical properties, bioimaging, and lipid droplet‐specific targeting capability of tailored BODIPYs are also demonstrated, indicating their promising applications in biomedical research, medicinal chemistry, and material science.

Recent Advances in Organocatalytic Asymmetric Synthesis of Bicyclo[3.3.1]nonane Frameworks

The bicyclo[3.3.1]nonane ring represents an attractive yet challenging synthetic targets in the field of organic synthesis, especially in a stereocontrolled fashion. Over the past two decades, organocatalysis has emerged as an enabling technology for the facile construction of enantioenriched molecules with remarkably increasing complexity and diversity, and a myriad of chiral architectures containing bicyclo[3.3.1]nonane units were elegantly assembled through organocatalytic asymmetric transformations. This review summarizes recent advancements on this topic (mainly from 2010 to 2023), emphasizing the reaction types such as desymmetrization and cascade reactions of different prochiral starting materials toward various chiral bicyclo[3.3.1]nonanes as well as their aza, oxa and thio derivatives. Meanwhile, the synthetic strategy, reaction mechanism, substrate scope and synthetic applications of these catalytic reactions are also discussed. We hope that this review will motivate further development and application of organocatalytic asymmetric synthesis of bicyclo[3.3.1]nonane frameworks.