Organocatalytic asymmetric deoxygenation of sulfones to access chiral sulfinyl compounds

Ionic Hydrogen Bond-Assisted Catalytic Construction of Nitrogen Stereogenic Center via Formal Desymmetrization of Remote Diols

The control of noncarbon stereogenic centers is of profound importance owing to their enormous interest in bioactive compounds and chiral catalyst or ligand design for enantioselective synthesis. Despite various elegant approaches have been achieved for construction of S-, P-, Si- and B-stereocenters over the past decades, the catalyst-controlled strategies to govern the formation of N-stereogenic compounds have garnered less attention. Here, we disclose the first organocatalytic approach for efficient access to a wide range of nitrogen-stereogenic compounds through a desymmetrization approach. Intriguingly, the pro-chiral remote diols, which are previously not well addressed with enantiocontrol, are well differentiated by potent chiral carbene-bound acyl azolium intermediates. Preliminary studies shed insights on the critical importance of the ionic hydrogen bond (IHB) formed between the dimer aggregate of diols to afford the chiral N-oxide products that feature a tetrahedral nitrogen as the sole stereogenic element with good yields and excellent enantioselectivities. Notably, the chiral N-oxide products could offer an attractive strategy for chiral ligand design and discovery of potential antibacterial agrochemicals.

Asymmetric 2,3-Addition of Sulfinylamines with Arylboronic Acids Enabled by Nickel Catalysis

Sulfinamides have been widely used in organic synthesis, with research on their preparation spanning more than a century. Despite advancements in catalytic methodologies, creating sulfur stereocenters within these molecules remains a significant challenge. In this study, we present an effective and versatile method for synthesizing a diverse range of S-chirogenic sulfinamides through catalytic asymmetric aryl addition to sulfinylamines. By utilizing a nickel complex as a catalyst, this process exhibits impressive enantioselectivity and can incorporate various arylboronic acids at the sulfur position. The resulting synthetic sulfinamides are stable and highly adaptable, allowing for their conversion to a variety of sulfur-containing compounds. Our study also incorporates detailed experimental and computational studies to elucidate the reaction mechanism and factors influencing enantioselectivity.

Syntheses and reactivities of strained fused-ring metallaaromatics containing planar eleven-carbon chains

Carbolong complexes are one of the primary types of metallaaromatics, and they include metallapentalynes and metallapentalenes. A series of 7C-10C and 12C-carbolong complexes with planar ligand skeletons respectively containing 7-10 and 12 carbon atoms in their backbones, have been previously reported. Herein, two classes of strained substances, metallabenzyne-fused metallapentalenes and metallabenzene-fused metallapentalynes, were prepared, both representing 11C-carbolong complexes with a planar carbon-chain ligand. Furthermore, the former type is also the carbolong derivatives containing a metallabenzyne skeleton, another primary metallaaromatic framework. Metallabenzyne-fused metallapentalenes show versatile reactivities, and the most interesting one is the metal carbyne bond shift from a 6-membered to a more strained 5-membered ring, affording the above-mentioned metallabenzene-fused metallapentalyne. This work makes carbolong chemistry more complete, and provides a method to achieve metallabenzynes, which is anticipated to concurrently advance the development of these two types of metallaaromatics.

Organocatalytic skeletal reorganization for enantioselective synthesis of S-stereogenic sulfinamides

The enantioselective synthesis of S-stereogenic sulfinamides has garnered considerable attention due to their structural and physicochemical properties. However, catalytic asymmetric synthesis of sulfinamides still remains daunting challenges, impeding their broad application in drug discovery and development. Here, we present an approach for the synthesis of S-stereogenic sulfinamides through peptide-mimic phosphonium salt-catalyzed asymmetric skeletal reorganization of simple prochiral and/or racemic sulfoximines. This methodology allows for the facile access to a diverse array of substituted sulfinamides with excellent enantioselectivities, accommodating various substituent patterns through desymmetrization or parallel kinetic resolution process. Mechanistic experiments, coupled with density functional theory calculations, clarify a stepwise pathway involving ring-opening and ring-closing processes, with the ring-opening step identified as crucial for achieving stereoselective control. Given the prevalence of S-stereogenic centers in pharmaceuticals, we anticipate that this protocol will enhance the efficient and precise synthesis of relevant chiral molecules and their analogs, thereby contributing to advancements in drug discovery.

Enantioselective Synthesis of Sulfinamidines via Asymmetric Nitrogen Transfer from N-H Oxaziridines to Sulfenamides

Sulfinamidines are promising aza-SIV chiral building blocks in asymmetric synthesis and drug discovery. However, no report has documented their enantioselective synthesis. Here we present an enantioselective synthesis of sulfinamidines via electrophilic amination of sulfenamides using an enantiopure N-H oxaziridine. The resulting enantiomerically enriched primary sulfinamidines are configurationally stable at 90 °C in solution and show remarkable stability against organic acids and bases under non-aqueous conditions. We also demonstrate a one-pot, three-component, enantioselective synthesis of sulfinamides using N-H oxaziridine reagents.

Recent advances in catalytic asymmetric synthesis

Asymmetric catalysis stands at the forefront of modern chemistry, serving as a cornerstone for the efficient creation of enantiopure chiral molecules characterized by their high selectivity. In this review, we delve into the realm of asymmetric catalytic reactions, which spans various methodologies, each contributing to the broader landscape of the enantioselective synthesis of chiral molecules. Transition metals play a central role as catalysts for a wide range of transformations with chiral ligands such as phosphines, N-heterocyclic carbenes (NHCs), etc., facilitating the formation of chiral C-C and C-X bonds, enabling precise control over stereochemistry. Enantioselective photocatalytic reactions leverage the power of light as a driving force for the synthesis of chiral molecules. Asymmetric electrocatalysis has emerged as a sustainable approach, being both atom-efficient and environmentally friendly, while offering a versatile toolkit for enantioselective reductions and oxidations. Biocatalysis relies on nature's most efficient catalysts, i.e., enzymes, to provide exquisite selectivity, as well as a high tolerance for diverse functional groups under mild conditions. Thus, enzymatic optical resolution, kinetic resolution and dynamic kinetic resolution have revolutionized the production of enantiopure compounds. Enantioselective organocatalysis uses metal-free organocatalysts, consisting of modular chiral phosphorus, sulfur and nitrogen components, facilitating remarkably efficient and diverse enantioselective transformations. Additionally, unlocking traditionally unreactive C-H bonds through selective functionalization has expanded the arsenal of catalytic asymmetric synthesis, enabling the efficient and atom-economical construction of enantiopure chiral molecules. Incorporating flow chemistry into asymmetric catalysis has been transformative, as continuous flow systems provide precise control over reaction conditions, enhancing the efficiency and facilitating optimization. Researchers are increasingly adopting hybrid approaches that combine multiple strategies synergistically to tackle complex synthetic challenges. This convergence holds great promise, propelling the field of asymmetric catalysis forward and facilitating the efficient construction of complex molecules in enantiopure form. As these methodologies evolve and complement one another, they push the boundaries of what can be accomplished in catalytic asymmetric synthesis, leading to the discovery of novel, highly selective transformations which may lead to groundbreaking applications across various industries.

Synthesis of S(IV)-Stereogenic Chiral Thio-Oxazolidinones via Palladium-Catalyzed Asymmetric [3+2] Annulations

Organic molecules bearing chiral sulfur stereocenters exert a great impact on asymmetric catalysis and synthesis, chiral drugs, and chiral materials. Compared with acyclic ones, the catalytic asymmetric synthesis of thio-heterocycles has largely lagged behind due to the lack of efficient synthetic strategies. Here we establish the first modular platform to access chiral thio-oxazolidinones via Pd-catalyzed asymmetric [3+2] annulations of vinylethylene carbonates with sulfinylanilines. This protocol is featured by readily available starting materials, and high enantio- and diastereoselectivity. In particular, an unusual effect of a non-chiral supporting ligand on the diastereoselectivity was observed. Possible reaction mechanisms and stereocontrol models were proposed.

Construction of Asymmetric C-S Bonds via an Electrochemical Catalysis

Construction of asymmetric C-S bonds was realized via electrochemical catalysis in the presence of a chiral nickel complex. The reaction can be carried out with excellent stereoselectivity and great functional group tolerance. The corresponding products provide crucial precursors for some functional materials and pharmaceutical drugs.

Enantioselective sulfur(VI) fluoride exchange reaction of iminosulfur oxydifluorides

Linkage chemistry and functional molecules derived from the stereogenic sulfur(VI) centre have important applications in organic synthesis, bioconjugation, drug discovery, agrochemicals and polymeric materials. However, existing approaches for the preparation of optically active S(VI)-centred compounds heavily rely on synthetic chiral S(IV) pools, and the reported linkers of S(VI) lack stereocontrol. A modular assembly method, involving sequential ligand exchange at the S(VI) centre with precise control of enantioselectivity, is appealing but remains elusive. Here we report an asymmetric three-dimensional sulfur(VI) fluoride exchange (3D-SuFEx) reaction based on thionyl tetrafluoride gas (SOF4). A key step involves the chiral ligand-induced enantioselective defluorinative substitution of iminosulfur oxydifluorides using organolithium reagents. The resulting optically active sulfonimidoyl fluorides allow for further stereospecific fluoride-exchange by various nucleophiles, thereby establishing a modular platform for the asymmetric SuFEx ligation and the divergent synthesis of optically active S(VI) functional molecules.

Nickel-Catalyzed Enantioselective Synthesis of Dienyl Sulfoxide

Sulfoxides are widely used in the pharmaceutical industry and as ligands in asymmetric catalysis. However, the efficient asymmetric synthesis of this structural motif remains limited. In this study, we disclosed a Ni-catalyzed enantioconvergent reaction that utilizes both racemic allenyl carbonates and β-sulfinyl esters. Our method employs cheap and more sustainable Ni(II) as a precatalyst and successfully overcomes the challenging poisoning effect and instability of sulfenate generated in situ. This enables the synthesis of a series of dienyl sulfoxides with enantioselectivity of up to 98 % ee. The product exhibits tremendous potential in various applications, including diastereoselective Diels-Alder reactions, coordination with transition metals, and incorporation into medicinal compounds, among others. Using a combination of experimental and computational methods, we have uncovered an interesting associated outersphere mechanism that contrasts with conventional mechanisms commonly observed in asymmetric transition metal catalysis.