Expedient Synthesis Research Articles

Building Ultrastrong, Tough and Biodegradable Thermoplastic Elastomers from Multiblock Copolyesters Via a “Reserve‐Release” Crystallization Strategy

AbstractSimultaneously attaining high strength and toughness has been a significant challenge in designing thermoplastic elastomers, especially biodegradable ones. In this context, we present a class of biodegradable elastomers based on multiblock copolyesters that afford extraordinary strength, toughness, and low‐strain resilience despite expedient chemical synthesis and sample processing. With the incorporation of the semi‐crystalline soft block and the judicious selection of block periodicity, the thermoplastic materials feature low quiescent crystallinity (“reserve”) albeit with vast potential for strain‐induced crystallization (“release”), resulting in their significantly enhanced ultimate strength and energy‐dissipating capabilities. Moreover, a breadth of mechanical responses of the materials – from reinforced elastomers to shape‐memory materials to toughened thermoplastics – can be achieved by orthogonal variation of segment lengths and ratios. This work and the “reserve‐release” crystallization strategy herein highlight the double crystalline multiblock chain architecture as a potential avenue towards reconciling the strength‐toughness trade‐off in thermoplastic elastomers and can possibly be extended to other biodegradable building blocks to deliver functional materials with diverse mechanical performances.

Building Ultrastrong, Tough and Biodegradable Thermoplastic Elastomers from Multiblock Copolyesters Via a "Reserve-Release" Crystallization Strategy.

Simultaneously attaining high strength and toughness has been a significant challenge in designing thermoplastic elastomers, especially biodegradable ones. In this context, we present a class of biodegradable elastomers based on multiblock copolyesters that afford extraordinary strength, toughness, and low-strain resilience despite expedient chemical synthesis and sample processing. With the incorporation of the semi-crystalline soft block and the judicious selection of block periodicity, the thermoplastic materials feature low quiescent crystallinity ("reserve") albeit with vast potential for strain-induced crystallization ("release"), resulting in their significantly enhanced ultimate strength and energy-dissipating capabilities. Moreover, a breadth of mechanical responses of the materials - from reinforced elastomers to shape-memory materials to toughened thermoplastics - can be achieved by orthogonal variation of segment lengths and ratios. This work and the "reserve-release" crystallization strategy herein highlight the double crystalline multiblock chain architecture as a potential avenue towards reconciling the strength-toughness trade-off in thermoplastic elastomers and can possibly be extended to other biodegradable building blocks to deliver functional materials with diverse mechanical performances.

Photolytic ortho-Selective Amino Pyridylation of Aryl Isocyanates with N-Amino Pyridinium Ylides for the Synthesis of N-Arylsulfonyl Ureas.

Herein, we report an expedient synthesis of aryl sulfonyl ureas 4 and 5 from N-amino pyridinium ylides and aryl isocyanates. N-Aminopyridinium ylides 3 are synthesized via blue light-emitting diode irradiation of pyridine/isoquinoline and appropriate iminoiodinanes. The strategy involved a hitherto unknown carboamination of imine moieties (of aryl isocyanates) via a three-component reaction of pyridine derivatives/isoquinoline 1, N-aryl sulfonyl iminoiodinanes 2, and numerous aryl isocyanates at room temperature in 2-methyl tetrahydrofuran to afford the target compounds in moderate to excellent yields. N-Arylpyridinium ylides 3 (as intermediates) undergo a [3+2] cycloaddition with the aryl isocyanates followed by the aromatization of the pyridine/isoquinoline moiety to afford compounds 4. On the basis of the substitution pattern among the reactants, in some cases pyridine extrusion occurs during the reaction to afford depyridinylated aryl sulfonyl ureas 5. In general, isocyanates are used as dipolarophiles in [3+2] cycloaddition reactions. However, regioselective amino pyridylation of these species is a first. Control experiments and density functional theory calculations elucidate the reaction mechanism. The batch process of the protocol could be seamlessly transferred to the photoflow synthesis.

Catalytic Asymmetric Barbier Reaction of Ketones with Unactivated Alkyl Electrophiles.

The Barbier reaction is a reductive-type addition of an aldehyde or ketone with an organic electrophile in the presence of a terminal metal reductant, providing a straightforward and efficient method for carbon-carbon bond formation. This reaction possesses the advantage of circumventing the preparation of moisture- and air-sensitive organometallic reagents. However, the catalytic Barbier reaction of ketones to construct tetrasubstituted stereogenic centers is largely underdeveloped, despite its great potential for accessing synthetically challenging chiral tertiary alcohol. Particularly, the leveraging of unactivated alkyl electrophiles as coupling components is still rarely exploited. Herein, we disclose a photoredox-assisted cobalt-catalyzed asymmetric alkylative Barbier-type addition reaction of ketones to address the aforementioned challenges, thereby allowing for the construction of highly congested tetrasubstituted carbon centers. The alkyl addition fragments could be either readily accessible unactivated alkyl halides or redox-active esters generated through a decarboxylative pathway. Both types of alkyl electrophiles include primary, secondary, and tertiary ones, thus affording diverse enantioenriched tertiary alcohols with a broad substrate scope. This enantioselective protocol is applied for the expedient synthesis of core structure of Sofdra, a very recent FDA-approved drug in 2024. The newly developed bisoxazolinephosphine (NPN) ligand enables high enantioselectivity in this asymmetric reductive addition process.

Expeditious and selective synthesis of 2,4,5-trialkyl-1H-imdazoles and benzimidazoles via multicomponent one-pot reaction catalyzed by Schiff base dioxomolybdenum(VI) complex

Imidazoles and benzimidazoles are privileged heterocyclic compounds that can be extensively found in medicinal and materials chemistry, however, the experimental procedures for their synthesis are limited to multicomponent condensation reactions and normally are strongly dependent upon the desired substitution pattern, consequently several procedures with different conditions and catalysts are available in literature. Accordingly, the development of synthetic methodologies to afford these compounds remains a very attractive research problem. In this regard, dioxomolybdenum based catalysts are emerging as versatile and non-expensive reagents for a myriad of chemically relevant transformations. Within this context, an expedient and efficient synthesis of 2,4,5-trialkyl-1H-imidazoles and benzimidazoles from a multicomponent one-pot condensation has been developed with a tridentate Schiff base dioxomolybdenum(VI) complex, resulting in an efficient, simple and readily available catalyst to promote the aforementioned reaction. This reaction offers advantages such as good to excellent yields, good selectivity of products, low catalyst loadings and simple reaction work-up.

Expedient Decagram-Scale Synthesis of Robust Organic Cages That Bind Sulfate Strongly and Selectively in Water.

Selective anion recognition remains a key challenge in supramolecular chemistry: only a very small number of systems that can function in water are known, and these nearly always preferentially bind hydrophobic anions. In this work, we report three robust hexa-cationic cages that can be prepared on scales up to 14 g in two simple and high-yielding steps from commercially available materials. One of these cages displays unusually strong sulfate binding in water (Ka = 12,000 M-1), and demonstrates high selectivity for this anion over H2PO4-/HPO42- in DMSO/buffer mixtures. These results demonstrate that relatively large, three-dimensional supramolecular hosts can be prepared in high yields and on large scales, and can be highly potent receptors.

Nickel-Catalyzed, Aminoquinoline-Directed Chemo- and Regioselective Carboamination of Unactivated Olefins with Organoboronic Acids and Anthranils.

A nickel-catalyzed three-component carboamination of unactivated alkenes with organoboronic acids and anthranils has been achieved for the expedient synthesis of δ-aryl and γ-amino acid derivatives. The 8-aminoquinoline (AQ) directing group is crucial for the success of the reaction, and anthranil serves as an arylnitrene precursor in this conversion. This method features mild reaction conditions, good chemo- and regioselectivity, and a broad substrate scope with good functional group tolerance.

Rh(III)-Catalyzed Regioselective Alkyne Insertion in the Context of C-H Activation and Lactonization Reactions: Synthesis of Fused 1,2-Oxaphospholenes.

Herein, we report an expedient synthesis of fused phosphorus-containing heterocycles via Rh-catalyzed cascade C-H activation, alkyne insertion, and lactonization reactions. The substrate scope and the group tolerance are good, as various substituted benzoic acids, N-methoxybenzamides, and 2-phenylindoles could go through the reactions smoothly to afford the corresponding products in moderate to high yields. Additionally, excellent regioselectivities are shown in the alkyne insertion with the assistance of an electron-withdrawing phosphonate group.

Stereoselective Synthesis of anti-2,4-Disubstituted Tetrahydrofurans via a Pd-Catalyzed Hayashi-Heck Arylation and Rh-Catalyzed Hydroformylation Sequence.

A catalytic, two-step protocol for the expedient synthesis of anti-2,4-disubstituted tetrahydrofurans is described. In the first step, an enantioselective and regioselective Pd-catalyzed Hayashi-Heck arylation was developed using (R)-hexaMeOBiphep to generate 5-aryl-2,3-dihydrofurans. A subsequent Rh-catalyzed hydroformylation step proceeds at low Rh loading with high regio- and diastereoselectivity for the anti-2,4-disubstituted tetrahydrofuran isomer. Key to the development of the hydroformylation reaction was the utilization of either (R)-Me-i-Pr-INDOLphos or (R,R)-Ph-BPE to control the regioselectivity and provide the kinetic product isomer.

Expedient synthesis of 8-membered azasultams: A combined synthetic, DFT, and in vitro study

Herein we describe the novel approach to the synthesis of functionalized ind(az)olo-fused 1,2,4-thiadiazocine 1,1-dioxides through the CSIC (Carbanion-mediated Sulfonate (Sulfonamide) Intermolecular Coupling (Intramolecular Cyclization) reaction strategy. 1,2,4-Thiadiazocine 1,1-dioxides (put simply 8-membered azasultams) are increasingly popular but quite underrepresented in the literature compounds, were prepared in two simple steps and good yield from readily available reagents. Particularly, the alkylation of 7-functionalized ind(az)oles with N-(chloromethyl)-N-methylmethanesulfonamide gave the corresponding N-((1H-ind(az)ol-1-yl)methyl)-N-methylmethane-sulfonamides which underwent base-mediated cyclization affording the target 8-membered azasultams. The method worked well and provided azasultams decorated with a set of synthetically valuable handles. The conducted DFT calculations explained and rationalized the experimental data thus allowing us to formulate the rules of the structure‒activity relationship. Despite the prepared compounds showing weak cytotoxicity against the MDA-MB-231 breast cancer cell line, they are considered novel building blocks and perspective pharmacological templates prone to further optimization.

Expedient Synthesis of Thermally Stable Acyclic Amino(haloaryl)carbenes: Experimental and Theoretical Evidence of “Push–Pull” Stabilized Carbenes

Expedient Synthesis of Thermally Stable Acyclic Amino(haloaryl)carbenes: Experimental and Theoretical Evidence of “Push–Pull” Stabilized Carbenes

Expedient Synthesis of Alkyl and Aryl Thioethers Using Xanthates as Thiol-Free Reagents.

Thioethers are critical in the fields of pharmaceuticals and organic synthesis, but most of the methods for synthesis alkyl thioethers employ foul-smelling thiols as starting materials or generate them as by-products. Additionally, most thiols are air-sensitive and are easily oxidized to produce disulfides under atmospheric conditions; thus, a novel method for synthesizing thioethers is necessary. This paper reports a simple, effective, green method for synthesizing dialkyl or alkyl aryl thioether derivatives using odorless, stable, low-cost ROCS2K as a thiol surrogate. This transformation offers a broad substrate scope and good functional group tolerance with excellent selectivity. The reaction likely proceeds via xanthate intermediates, which can be readily generated via the nucleophilic substitution of alkyl halides or aryl halides with ROCS2K under transition-metal-free and base-free conditions.

Fluoroalkylative Ketonization of Malononitrile-Tethered Alkenes via Nickel Electron-Shuttle and Lewis Acid Catalysis.

A binary Ni/Eu catalytic system has been developed, which enables an efficient reductive dicarbofunctionalization of unactivated alkenes with alkyl halides and malononitriles. The combination of Ni electron-shuttle catalysis with Eu(OTf)3, a non-redox-type Lewis acid, effectively activates the iminyl radicals, enabling the direct formation of the C(sp3)-C(sp3) bond and β-ketonitrile functionality across a variety of C═C double bonds. This reaction allows for the expedient synthesis of densely functionalized cyclic β-ketonitriles bearing all-carbon quaternary centers.

Nickel-catalysed enantioselective alkene dicarbofunctionalization enabled by photochemical aliphatic C–H bond activation

The development of novel strategies to rapidly construct complex chiral molecules from readily available feedstocks is a long-term pursuit in the chemistry community. Radical-mediated alkene difunctionalizations represent an excellent platform towards this goal. However, asymmetric versions remain highly challenging, and more importantly, examples featuring simple hydrocarbons as reaction partners are elusive. Here we report an asymmetric three-component alkene dicarbofunctionalization capitalizing on the direct activation of C(sp3)–H bonds through the combination of photocatalysed hydrogen atom transfer and nickel catalysis. This protocol provides an efficient platform for installing two vicinal carbon–carbon bonds across alkenes in an atom-economic fashion, providing a wide array of high-value chiral α-aryl/alkenyl carbonyls and phosphonates, as well as 1,1-diarylalkanes from ubiquitous alkane, ether and alcohol feedstocks. This method exhibits operational simplicity, broad substrate scope and excellent regioselectivity, chemoselectivity and enantioselectivity. The compatibility with bioactive motifs and expedient synthesis of pharmaceutically relevant molecules highlight the synthetic potential of this protocol.

Harmonious Accommodation among Coexisting Multicultural Ethical Frameworks through Confrontation

This paper interrogates the skepticism surrounding comparative ethics, particularly the question of its relevance in a world where ethical decision-making processes are primarily presumed to be dictated by one universalist culture. The paper argues that all cultures are inherently intercultural, evidenced by the historical coexistence of ideas and practices. Post-comparative ethics, which emphasizes the situational application of intellectual comparison and integration, is inevitable for postcolonial, non-Western societies. Historically, societies have navigated a variety of ethical frameworks, with some, like medieval Chinese society, embracing a plurality of beliefs. This pluralism is exemplified by the harmonious accommodation (yuanrong 圓融) of Confucianism, Daoism, and Buddhism. Using the example of Song Dynasty Chan master Dahui Zonggao 大慧宗杲, this article illustrates that intercultural ethics can be both diverse and sincere. Dahui’s pluralistic approach demonstrates that sincere commitment to multiple ethical systems is possible in our multicultural situation. I will discuss common approaches to the multicultural situation, such as expedient synthesis, theoretical synthesis, and crude syncretism, before illustrating the advantage of Dahui’s kanhua 看話禪method as harmonious accommodation through confrontation. This underscores the importance of shifting the debate from “Why compare?” to “How to compare?” in achieving the accommodation of different ethical frameworks.

Facile Synthesis and First Antifungal Exploration of Tetracyclic Meroterpenoids: (+)-Aureol, (-)-Pelorol, and Its Analogs.

As an important bioactive molecular backbone, drimane meroterpenoids have drawn a great deal of attention from both pharmacologists and chemists. Inspired by the prevalidated success of conformational restriction in the discovery of novel pharmaceutical leads, two distinct tetracyclic drimane meroterpenoids, (-)-pelorol and (+)-aureol, were synthesized from the inexpensive starting material (-)-sclareol through 10 and 8 steps with 5.6% and 5.4% overall yield, respectively. The mild conditions, operational facility, and scalability enabled the expedient synthesis and biological exploration of not only natural products themselves but also their mimics. The first agrochemical exploration showed (-)-pelorol and (+)-aureol possessed good antifungal activity against Rhizoctonia solani, with EC50 values of 7.7 and 6.9 μM, respectively. This revealed that tetracyclic drimane meroterpenoids are valuable models for antifungal lead discovery.

Expedient Synthesis of Axially and Centrally Chiral Diaryl Ethers via Cobalt-Catalyzed Photoreductive Desymmetrization

Expedient Synthesis of Axially and Centrally Chiral Diaryl Ethers via Cobalt-Catalyzed Photoreductive Desymmetrization

Water vs. Organic Solvents: Water-Controlled Divergent Reactivity of 2-Substituted Indoles.

Water is not a good solvent for most organic compounds, yet water can offer many benefits to some organic reactions, hence enriching organic chemistry. Herein, the unique divergent reactivity of 2-substituted indoles with ⋅NO sources is presented. The amount of water solvent was harnessed for a scalable, benign, and expedient synthesis of indolenine oximes, albeit with water's inability to dissolve the reactants. 2-Methoxyethyl nitrite, which has been tailored for reactions in water, empowered this protocol by enhancing the product selectivity. We further report on chemoselective transformations of the products that rely on their structural features. Our findings are expected to offer access to an underexplored chemical space. The platform is also applicable to oximinomalonate synthesis. Mechanistic studies revealed the important role of water in the reversal of stability between oxime and nitroso compounds, promoting the proton transfer.

Enantioselective Synthesis of the 1,3‐Dienyl‐5‐Alkyl‐6‐Oxy Motif: Method Development and Total Synthesis

AbstractThe 1,3‐dienyl‐5‐alkyl‐6‐oxy motif is widely found in various types of bioactive natural products. However, present synthesis is mainly non‐asymmetric which relied upon different olefination or transition metal‐catalyzed cross‐coupling reactions using enantioenriched precursors. Herein, based upon a newly developed enantioselective α‐alkylation of conjugated polyenoic acids, a variety of 1,3‐dienyl‐5‐alkyl‐6‐oxy motif (with E‐configured internal olefin) was generated as the corresponding α‐adducts in a highly enantioselective and diastereoselective manner. Utilizing 1,3‐dienyl‐5‐alkyl‐6‐oxy motif as key intermediates, we further demonstrated their synthetic potential by expedient total syntheses of three types of natural products (glutarimide antibiotics, α‐pyrone polyketides and Lupin alkaloids) within 4–7 steps.

Enantioselective Synthesis of the 1,3-Dienyl-5-Alkyl-6-Oxy Motif: Method Development and Total Synthesis.

The 1,3-dienyl-5-alkyl-6-oxy motif is widely found in various types of bioactive natural products. However, present synthesis is mainly non-asymmetric which relied upon different olefination or transition metal-catalyzed cross-coupling reactions using enantioenriched precursors. Herein, based upon a newly developed enantioselective α-alkylation of conjugated polyenoic acids, a variety of 1,3-dienyl-5-alkyl-6-oxy motif (with E-configured internal olefin) was generated as the corresponding α-adducts in a highly enantioselective and diastereoselective manner. Utilizing 1,3-dienyl-5-alkyl-6-oxy motif as key intermediates, we further demonstrated their synthetic potential by expedient total syntheses of three types of natural products (glutarimide antibiotics, α-pyrone polyketides and Lupin alkaloids) within 4-7 steps.