Synthesis and applications of tert-butanesulfinamide

One-Pot Synthesis of Benzoxazoles and Sulfoxides: Complete Utilization of Diaryl Sulfoxides

Synthesis of 2-aryl benzoxazoles and aryl sulfoxide derivatives in a one-pot process has been developed via the palladium-catalyzed cross-coupling of diaryl sulfoxides with benzoxazoles, followed by trapping the remaining sulfenate anions with different electrophilic reagents. The reaction involves the C-S and C-H bond activation and the C-C and C-S bond formation. The protocol allows a broad scope of substrates, functional group tolerance, and scalability.

Diastereoselective synthesis of (Z)-fluoroalkene dipeptide isosteres utilizing chiral auxiliaries

An efficient method for diastereo-controlled synthesis of (Z)-fluoroalkene dipeptide isosteres (FADIs) was developed. Two chiral centers were constructed by applying our synthetic methodology for chloroalkene dipeptide isosteres (CADIs) using Ellman's imine for corresponding to the N-terminal amino acid residues and Oppolzer's sultam for corresponding to the C-terminal amino acid residues, affording dipeptidomimetic in a stereocontrolled manner with high diastereoselectivity.

Asymmetric amination of alkyl radicals with two minimally different alkyl substituents

Differentiating between similar alkyl groups is a major challenge in asymmetric catalysis. Achieving enantiocontrol over unactivated prochiral alkyl radicals is even more difficult owing to their high reactivity and limited interactions with chiral catalysts. In this study, we report a copper-catalyzed asymmetric amination of unactivated prochiral secondary alkyl radicals, using specifically designed chiral anionic multidentate ligands in a radical substitution reaction. This approach efficiently produces highly enantioenriched α-chiral alkyl amines and facilitates the enantioselective formal synthesis of a series of important drug molecules. Mechanistic studies reveal that bulky peripheral modifications on the ligands help create a truncated cone-shaped chiral pocket, enabling precise enantiodiscrimination through steric hindrance and noncovalent interactions. This strategy holds broad potential for asymmetric transformations involving diverse unactivated prochiral alkyl radicals and nucleophiles.

Modular synthesis of bis-α-chiral amines using Ellman sulfinamide for consecutive S-to-C chirality induction/transfer

Amines are ubiquitous components in pharmaceuticals. Increasing saturated substitutions (sp3-hybridized carbon) at the amino center and the number of chiral centers can enrich the molecular diversity and chemical space, ultimately enhancing the success of drug development. However, the synthesis of such advanced amines is challenging due to a higher level of structural complexity and stereo-control. Here, we report a modular protocol for short de novo synthesis of bis-α-chiral amines. This protocol uses commercially available Ellman sulfinamide, tert-butanesulfinamide (tBS), as the exclusive chiral source to selectively produce all possible stereoisomers. Sequential formation of contiguous α-amino chiral carbons is achieved by chirality induction and transfer mechanisms that are both enabled by tBS, the stereoselective imine functionalization and alkyne-participated rearrangement reaction. The second step we developed is crucial for high diastereoselectivity, which is problematic in previous methods. The other coupling partners used in this protocol are abundant feedstocks, providing desirable chemical diversity in the products.

Asymmetric reductive arylation and alkenylation to access S-chirogenic sulfinamides

The study of the stereochemistry of organic sulfur compounds has been ongoing for over a century, with S-chirogenic pharmacophores playing an essential role in drug discovery within bioscience and medicinal chemistry. Traditionally, the synthesis of sulfinamides featuring stereogenic sulfur(IV) centers involves a complex, multistep process that often depends on chiral auxiliaries or kinetic resolution. Here, we introduce an effective and versatile method for synthesizing diverse classes of S-chirogenic sulfinamides through selective aryl and alkenyl addition to sulfinylamines. This process is catalysed by a chiral nickel or cobalt complex under reductive conditions, and eliminating the need for preformed organometallic reagents. The method facilitates the incorporation of a diverse array of aryl and alkenyl halides at the sulfur position, enabling their integration into various biologically significant sulfur pharmacophores. Our detailed mechanistic investigations and density functional theory calculations provide insights into the reaction pathway, particularly highlighting the enantiocontrol mode during addition process.

Anionic Stereogenic-at-Cobalt(III) Complex-Enabled Asymmetric Oxidation of N,N-Dialkyl Sulfenamides

An asymmetric oxidation of N,N-dialkyl sulfenamides is exhibited by using anionic stereogenic-at-cobalt(III) complexes as catalysts. This protocol provides an alternative approach to access a diverse set of chiral tertiary sulfinamides with high enantioselectivities (24 examples, up to 94:6 e.r.). Additionally, control experiments suggest that this protocol could be accomplished through a chiral cationic S(IV) intermediate.

Regioselective Aryne Annulations of N-Tosyl-2-enamides and N-tert-Butylsulfinyl-2-enamides for the Construction of Dihydroquinolin-4-one and Chroman-4-imine Units

A regioselective synthesis of the dihydroquinolin-4-one 4 is achieved from the aryne-mediated annulation of an o-(trimethylsilyl)aryl triflate 1 with N-tosyl-2-enamide 2 in the presence of TBAT in toluene, whereas the chroman-4-imine 5 is formed from the reaction of 1 with N-(tert-butylsulfinyl)-2-enamide 3 and TBAF in THF. Governing factors for regioselectivity have been accounted for as strong steric and electronic effects between N-toluenesulfonyl and N-tert-butylsulfinyl groups in 2 and 3. The methods described herein are successful with various substrates 1 with 2 or 3 in high levels of regioselectivity, and diastereoselectivity for 5.

A Fluorescent Probe Enables the Discovery of Improved Antagonists Targeting the Intracellular Allosteric Site of the Chemokine Receptor CCR7

Intracellular ligands of G protein-coupled receptors (GPCRs) are gaining significant interest in drug discovery. Here, we report the development of the fluorescent ligand Mz437 (4) targeting the CC chemokine receptor CCR7 at an intracellular allosteric site. We demonstrate its experimental power by applying 4 to identify two improved intracellular CCR7 antagonists, SLW131 (10) and SLW132 (21m), developed by converting two weakly active antagonists into single- or double-digit nanomolar ligands with minimal modifications. The thiadiazoledioxide 10 was derived from the CCR7 antagonist Cmp2105 by removing a methyl group from the benzamide moiety, while the squaramide 21m was obtained from the CXCR1/CXCR2 antagonist and clinical candidate navarixin by replacing the ethyl substituent by a tert-butyl group to engage a lipophilic subpocket. We show that 10 and 21m qualify to probe CCR7 biology in recombinant and primary immune cells and expect our novel probes to facilitate the design of next-generation intracellular CCR7 ligands.

Synthesis of chiral N-free sulfinamides by asymmetric condensation of stable sulfinates and ammonium salts

Herein, we developed a practical approach using stable, cost-effective ammonium salts with an organic base to generate anhydrous ammonia for asymmetric sulfinylation, achieving a broad range of enantioenriched sulfinamides with excellent yields and optical purity. Additionally, these sulfinamide products serve as versatile precursors for S-stereogenic functional molecules with potential in organic synthesis and drug discovery.

Photoredox-catalyzed deoxygenative radical transformation of alcohols to sulfinamides

Sulfinamides play a crucial role in organic synthesis and pharmaceuticals. In this study, we introduce a highly effective method for the deoxygenative radical addition to N-tritylsulfinylamine, which produces sulfinamides via photoredox catalysis. This method is compatible with a diverse array of functional groups and the resulting sulfonamides were achieved in moderate to high yields. Furthermore, the synthetic applications to access various sulfur(vi)-centered functional groups highlight the practicality of this approach.

Enantiopure Turbo Chirality Targets in Tri-Propeller Blades: Design, Asymmetric Synthesis, and Computational Analysis

Enantiopure turbo chirality in small organic molecules, without other chiral elements, is a fascinating topic that has garnered significant interest within the chemical and materials science community. However, further research into and application of this concept have been severely limited by the lack of effective asymmetric tools. To date, only a few enantiomers of turbo chiral targets have been isolated, and these were obtained through physical separation using chiral HPLC, typically on milligram scales. In this work, we report the first asymmetric approach to enantiopure turbo chirality in the absence of other chiral elements such as central and axial chirality. This is demonstrated by assembling aromatic phosphine oxides, where three propeller-like groups are anchored to a P(O) center via three axes. Asymmetric induction was successfully carried out using a chiral sulfonimine auxiliary, with absolute configurations and conformations unambiguously determined by X-ray diffraction analysis. The resulting turbo frameworks exhibit three propellers arranged in either a clockwise (P,P,P) or counterclockwise (M,M,M) configuration. In these arrangements, the bulkier sides of the aromatic rings are oriented toward the oxygen atom of the P=O bond rather than in the opposite direction. Additionally, the orientational configuration is controlled by the sulfonimine auxiliary as well, showing that one of the Naph rings is pushed away from the auxiliary group (-CH2-NHSO2-tBu) of the phenyl ring. Computational studies were conducted on relative energies for the rotational barriers of a turbo target along the P=O axis and the transition pathway between two enantiomers, meeting our expectations. This work is expected to have a significant impact on the fields of chemistry, biomedicine, and materials science in the future.

Stereoselective Vinylogous Aza-Pummerer Reaction of β,β-Disubstituted Enesulfinamides

Treatment of multisubstituted NH-enesulfinamides with tosyl isocyanate (TsNCO) at room temperature results in the formation of α-tosylcarbamoyloxy N-sulfenyl ketimines with high enantioselectivity. This process is believed to proceed via a vinylogous aza-Pummerer-type reaction pathway in which the sulfinyl oxygen atom in the enesulfinamides undergoes nucleophilic attack on tosyl isocyanate, triggering the subsequent transformations that enable the transfer of chirality from sulfur to carbon.

Deoxygenative photochemical alkylation of secondary amides enables a streamlined synthesis of substituted amines

Secondary amines are vital functional groups in pharmaceuticals, agrochemicals, and natural products, necessitating efficient synthetic methods. Traditional approaches, including N-monoalkylation and reductive amination, suffer from limitations such as poor chemoselectivity and complexity. Herein, we present a streamlined deoxygenative photochemical alkylation of secondary amides, enabling the efficient synthesis of α-branched secondary amines. Our method leverages triflic anhydride-mediated semi-reduction of amides to imines, followed by a photochemical radical alkylation step. This approach broadens the synthetic utility of amides, facilitating late-stage modifications of drug-like molecules and the synthesis of saturated N-substituted heterocycles. The pivotal role of flow technology in developing a scalable and robust process underscores the practicality of this method, significantly expanding the organic chemist's toolbox for complex amine synthesis.

Unlocking Chiral Sulfinimidoyl Electrophiles: Asymmetric Synthesis of Sulfinamides Catalyzed by Anionic Stereogenic-at-Cobalt(III) Complexes

Asymmetric catalysis involving a sulfoxide electrophile intermediate presents an efficient methodology for accessing stereogenic-at-sulfur compounds, such as sulfinate esters, sulfinamides, etc., which have garnered increasing attention in modern pharmaceutical sciences. However, as the aza-analog of sulfoxide electrophiles, the asymmetric issues about electrophilic sulfinimidoyl species remain largely unexplored and represent a significant challenge in sulfur stereochemistry. Herein, we exhibit an anionic stereogenic-at-cobalt(III) complex-catalyzed asymmetric synthesis of chiral sulfinamides via chiral sulfinimidoyl iodide intermediates. Mechanistic investigations reveal that the catalytic cycle is initiated by asymmetric oxidative iodination, generating sulfinimidoyl iodides. These active intermediates subsequently undergo an enantiospecific nucleophilic substitution with water, affording a diverse array of enantioenriched sulfinamides. Notably, these sulfinamides exhibit promising antifungal activities against Sclerotinia sclerotiorum and serve as ideal platform molecules facilitating the stereospecific transformation into various stereogenic aza-sulfur compounds.

Reductive sulfinylation by nucleophilic chain isomerization of sulfonylpyridinium

Sulfur-containing units are fundamental components widely found in bioactive compounds, prompting notable efforts toward developing synthetic methodologies for incorporating sulfur functionality into organic precursors. The synthesis of sulfinate esters and sulfinamides has garnered significant interest owing to their immense potential for applications, especially in drug development. However, most existing synthetic protocols suffer from some limitations. To address these challenges, we herein present a practical and efficient approach for the reductive sulfinylation of diverse nucleophiles with sulfonylpyridinium salts (SulPy) through the nucleophilic chain substitution, namely SNC reaction, which involves S(VI) to S(IV) nucleophilic chain isomerization process. These versatile sulfinylation reagents can be readily accessed from diverse commercially available resourses. The late-stage modification of complex molecules and the ability to rapidly synthesize numerous sulfinyl bioisosteres of various drugs highlights the utility of this protocol.

Stereoselective Enesulfinamide-Sulfinylimine Tautomerization of β,β-Disubstituted Enesulfinamides

In the presence of cesium fluoride and organosilicon reagent, β,β-disubstituted NH-enesulfinamides undergo stereoselective enesulfinamide-sulfinylimine tautomerization at room temperature, resulting in the formation of α-branched N-sulfinyl ketimines in good yields with high stereoselectivity. A variety of acyclic ketone surrogates α-substituted with two electronically and sterically similar groups (e.g., methyl and ethyl), which are typically challenging to access through conventional protocols involving stereoselective protonation of enolates and their equivalents, have been effectively synthesized.

Discovery of Staircase Chirality through the Design of Unnatural Amino Acid Derivatives

Chirality has garnered significant attention in the scientific community since its discovery by Louis Pasteur over a century ago. It has been showing a profound impact on chemical, biomedical, and materials sciences. Significant progress has been made in controlling molecular chirality, as evidenced by the several Nobel Prizes in chemistry awarded in this area, particularly for advancements in the asymmetric catalytic synthesis of molecules with central and axial chirality. However, the exploration of new types of chirality has been largely stagnant for more than half a century, likely due to the complexity and challenges inherent in this field. In this work, we present the discovery of a novel type of chirality-staircase chirality as inspired by the design and synthesis of unnatural amino acid derivatives. The architecture of staircase chirality is characterized by 2 symmetrical phenyl rings anchored by a naphthyl pier, with the rings asymmetrically displaced due to the influence of chiral auxiliaries at their para positions. This unique staircase chiral framework has been thoroughly characterized using spectroscopic techniques, with its absolute configuration definitively confirmed by x-ray diffraction analysis. Remarkably, one of the staircase molecules exhibits 4 distinct types of chirality: central, orientational, turbo, and staircase chirality, a combination that has not been previously documented in the literature. Computational studies using density functional theory (DFT) calculations were conducted to analyze the relative energies of individual staircase isomers, and the results are in agreement with our experimental findings. We believe that this discovery will open up a new research frontier in asymmetric synthesis and catalysis, with the potential to make a substantial impact on the fields of chemistry, medicine, and materials science.

Asymmetric Synthesis of β-Ketoamides by Sulfonium Rearrangement

The synthesis of enantioenriched α-substituted 1,3-dicarbonyls remains a contemporary challenge in synthesis due to their tendency to undergo racemization via keto-enol tautomerization. Herein, we report a method to access enantioenriched β-ketoamides by a chiral sulfinimine-mediated [3,3]-sigmatropic sulfonium rearrangement. The transformation displays good chirality transfer, as well as excellent chemoselectivity and functional group tolerance. Diastereoselective reduction of the ketone moiety, also achievable in one-pot fashion, affords enantioenriched β-hydroxyamides.

Stereoselective Aminomethylation of β,β-Disubstituted Enesulfinamides: Asymmetric Construction of Less Accessible Acyclic α,α-Disubstituted α-Aminomethylated Ketimines

β,β-Disubstituted enesulfinamides undergo stereoselective nucleophilic addition to the formaldehyde imines, in situ formed from tosylmethylcarbamates, affording α-aminomethylated ketimines bearing a challenging acyclic quaternary stereocenter substituted by two sterically and electronically similar groups (e.g., Me and Et). The defined geometry of the C═C bond in the enesulfinamides, combined with the strong chiral induction offered by their chiral sulfinyl group, ensures precise stereocontrol during the formation of the new C-C bond.

The Latest Progress in the Chemistry of Daphniphyllum Alkaloids

Daphniphyllum alkaloids (DAs) are interesting molecules with rich molecular skeletons and diverse biological activities. Since their discovery, phytochemists have isolated, purified, and identified more than 350 DAs. Synthetic chemists, attracted by the structure and activity of DAs, have accomplished many elegant synthetic jobs. Herein, we summarize work on the isolation, structural identification, bioactivity testing, and synthesis of DAs from 2018 to 2023, with the aim of providing a reference for future studies.

Regio- and Enantioselective Nickel-Catalyzed Ipso- and Remote Hydroamination Utilizing Organic Azides as Amino Sources for the Synthesis of Primary Amines

Primary amines serve as key synthetic precursors to most other N-containing compounds, which are important in organic and medicinal chemistry. Herein, we present a NiH-catalyzed mild ipso- and remote hydroamination technique that utilizes organic azides as deprotectable primary amine sources. This strategy offers a highly flexible platform for the efficient construction of α-chiral branched primary amines, as well as linear primary amines.

Stereoselective Construction of Less-Accessible Acyclic Quaternary Carbon Stereocenters via Rhodium-Catalyzed Allylic Alkylation of β,β-Disubstituted Enesulfinamides

In the presence of Wilkinson's catalyst, the N-sulfinyl metalloenamines derived from NH-deprotonation of β,β-disubstituted enesulfinamides undergo nucleophilic allylic substitution with allyl carbonate, affording α-allylated ketimines with high stereoselectivity. These allylation products possess challenging acyclic quaternary stereocenters containing one allyl group and two alkyl groups that are both sterically and electronically similar (e.g., Me and Et). By utilizing appropriate stereoisomers of enesulfinamides, it becomes feasible to selectively access each of the four potential stereoisomers of the allylation products, thereby facilitating the selective synthesis of stereoisomers of α-tertiary chiral amines featuring a β-quaternary stereocenter through imino nucleophilic addition.

Green Synthesis of Morpholines via Selective Monoalkylation of Amines

Morpholines are common heterocycles in pharmaceutical and agricultural products, yet methods to synthesize them from 1,2-amino alcohols are inefficient. We report the simple, high yielding, one or two-step, redox neutral protocol using inexpensive reagents (ethylene sulfate and tBuOK) for the conversion of 1,2-amino alcohols to morpholines. Key to this methodology is the identification of general conditions that allow for the clean isolation of monoalkylation products derived from a simple SN2 reaction between an amine and ethylene sulfate. Experiments suggest that the degree of selectivity is dependent upon the structure of reacting 1,2-amino alcohol as well as the unique properties of ethylene sulfate. This method can be used for the synthesis of a variety of morpholines containing substituents at various positions, including 28 examples derived from primary amines and multiple examples contained in known active pharmaceutical ingredients. We have conducted multiple examples on >50 g scale. We have also demonstrated the formal synthesis of a morpholine from a simple primary amine using ethylene sulfate. Overall, while this new methodology has many environmental and safety benefits relative to the traditional methods used to prepare morpholines from 1,2-amino alcohols, the most striking feature is the facile selective monoalkylation of a variety of primary amines. We have also explored various reactions beyond those related to the synthesis of morpholines, including obtaining proof-of-principle that ethylene sulfate can be used for the synthesis of piperazines and as a 2-carbon electrophile for fragment couplings.

Cinchona Organocatalyzed Enantioselective Amination for Quaternized Serines as Tertiary Amides

Herein, we describe a Cinchona-aminocatalyzed enantioselective α-hydrazination of an α-formyl amide for the production of protected quaternized serines as tertiary amides with ee's of generally >98% and ≤99% yields. The proposed TS model supported by density functional theory calculations involves a quinuclidinium ion Brønsted acid-assisted delivery of DtBAD, which occurs from the Re face of an H-bonded enaminone when using a 9S-cinchonamine catalyst, resulting in a hydrazide with the R-configuration as determined by X-ray analysis.

Direct Asymmetric Synthesis of α-Aminoimines from 1,2-Bis-N-Sulfinylimines by Using Allyl Boronic Acids

A unique direct asymmetric synthesis of α-aminoimines is realized, through rapid and exclusive mono-allylation of chiral bis-N-sulfinylimines using allylboronic acids. The highly selective allylation was possible as electrophilic imine functional group in the product α-aminoimines remained unreactive towards allyl boronic acid nucleophiles. Notably, by varying the geometry and chiral auxiliary, all four isomers of the α-aminoimines were accessed from readily available precursors. A range of allyl nucleophiles, which are tricky to generate by other means possessing highly reactive functional groups also took part in this reaction, expanding the scope further. The applicability of the products α-aminoimines were further demonstrated by accessing a range of structurally diverse chiral cyclic and acyclic 1,2-diamines bearing adjacent stereocenters through addition of a second nucleophile or Prins-type cyclization by exploiting the nucleophilicity of the tethered alkene moiety. Moreover, the leaving group aptitude of sulfinyl auxiliary attached to imine, was exploited to access valuable chiral α-aminonitriles under thermal conditions without employing any reagents. Detailed DFT calculation revealed a chair-like transition state, arising from corresponding allylboroxine species, likely operating for the allylboration reaction across imine.

Practical Synthesis of Macrobicyclic Thiolincosamines

Scalable syntheses of the northern macrobicyclic thiolincosamine fragments of two structurally complex antibiotic candidates, BT-33 and cresomycin, are presented. A key transformation in each route is the highly diastereoselective addition of a putative allenylzinc nucleophile to a common Ellman sulfinimine intermediate using a zinc-promoted Barbier-type propargylation protocol that is detailed herein. These transformations proceed with dynamic kinetic resolution and use just 1.2 equiv of each respective propargyl bromide precursor.

A Dual Role for the N-Perfluorobutanesulfinamide Auxiliary in an Asymmetric Decarboxylative Mannich Reaction

Herein, we demonstrate that the enhanced electrophilicity of N-perfluorobutanesulfinamide auxiliary-derived imines enables a highly selective decarboxylative Mannich reaction under mild conditions. The molecular sieves-mediated transformation tolerates a broad substrate scope and produces chiral β-amino thioesters in high yield. Additionally, we demonstrate that the N-perfluoroalkyl sulfinyl group can function as a phase tag for fluorous purification, thus enabling the rapid isolation of the chiral amine products by solid-phase extraction. The synthetic utility of this method is illustrated by the synthesis of sitagliptin, ruspolinone, and the natural product negamycin.

A General and Scalable Method toward Enantioenriched C2-Substituted Azetidines Using Chiral tert-Butanesulfinamides

Diverse ranges of chiral nitrogen-containing heterocycles serve as a molecular toolbox for modulating a wide array of biological processes, but enantioenriched production of smaller chiral heterocycles is a bottleneck. There is a lack of general approaches for the stereoselective preparation of chiral 4-membered monocyclic C2-substituted azetidines, where many routes to different substitution types are possible, but no simple and common approach exists. To bridge this gap, inexpensive and widely available chiral tert-butanesulfinamides are harnessed for chiral induction with 1,3-bis-electrophilic 3-chloropropanal, providing a three-step approach to C2-substituted azetidines with aryl, vinyl, allyl, branched alkyl, and linear alkyl substituents. Eleven azetidine products are produced, and the approach is shown to be effective on a gram-scale with a single purification of the protected azetidine product in 44% yield over three steps in an 85:15 diastereomeric ratio. In most cases, the diastereomers are separable using normal phase chromatography, often resulting in previously elusive enantiopure azetidine products. Protected azetidines were shown to undergo rapid and efficient sulfinamide cleavage, producing an azetidine hydrochloride salt that was subjected to derivatization reactions, highlighting the method's applicability to medicinal chemistry approaches.

Diastereoselective Addition of Lithiated Allenyl Sulfones to Nonracemic Sulfinimines: Asymmetric Synthesis of Diverse Heterocycles

The addition of lithiated allenyl sulfones to nonracemic sulfinimines furnished sulfinamides possessing the allenyl sulfonyl moiety with excellent diastereoselectivity. The formed products are transformed into different heterocycles, including the synthesis of pyrroline, pyran, and functionalized benzopyran.

Amino Turbo Chirality and Its Asymmetric Control

A series of new targets containing 3 chiral elements of central, orientational, and turbo chirality have been designed and synthesized asymmetrically. The absolute configurations and conformations of these types of chirality were concurrently controlled by using chiral sulfonimine auxiliary and unambiguously determined by x-ray diffraction analysis. These targets include alpha unnatural amino acid derivatives, which may play an important role for drug design, discovery, and development. Three propellers of turbo framework are covalently connected to a chiral C(sp3) center via C(sp2)-C(sp3) bonding along with a C-N axis, while one of them is orientated away from the same carbon chiral center. The turbo or propeller chirality is characterized by 2 types of molecular arrangements of propellers, clockwise (PPP) and counterclockwise (MMM), respectively. The turbo stereogenicity was found to depend on the center chirality of sulfonimine auxiliary instead of the chiral C(sp3) center, i.e., (S)- and (R)-sulfinyl centers led to the asymmetric formation of PPP- and MMM-configurations, respectively. Computational studies were conducted on relative energies for rotational barriers of a turbo target along the C-N anchor and the transition pathway between 2 enantiomers meeting our experimental observations. This work is anticipated to have a broad impact on chemical, biomedical, and materials sciences in the future.

Catalyst Control over S(IV)-stereogenicity via Carbene-derived Sulfinyl Azolium Intermediates

Stereoselective synthesis utilizing small-molecule catalysts, particularly N-heterocyclic carbene (NHC), has facilitated swift access to enantioenriched molecules through diverse activation modes and NHC-bound reactive intermediates. While carbonyl derivatives, imines, and "activated" alkenes have been extensively investigated, the exploration of heteroatom-centered analogues of NHC-bound intermediates has long been neglected, despite the significant potential for novel chemical transformations they offer once recognized. Herein, we disclose a carbene-catalyzed new activation mode by generating unique sulfinyl azolium intermediates from carbene nucleophilic addition to in situ-generated mixed sulfinic anhydride intermediates. Combined experimental and computational mechanistic investigations pinpoint the chiral NHC-catalyzed formation of sulfinyl azolium intermediate as the enantio-determining step. The novel "S"-based carbene reactive intermediate imparts high efficiency for the catalytic construction of sulfur-stereogenic compounds, giving rise to sulfinate esters with high yields and enantioselectivities under mild conditions. Notably, distinct from most of the NHC-catalyzed enantioselective transformations focusing on the "C" central chiral products, our study realizes a unique carbene-catalyst control over chiral "S" stereocenters via direct asymmetric S-O bond formation for the first time. Furthermore, these sulfinyl-containing products could serve as versatile synthetic platforms for enantioenriched S-stereogenic functional molecules and exhibit remarkable antibacterial activities against rice plant pathogens, which is valuable for the development of novel agrochemical agents.

Thionyl fluoride as a sulfur(IV) SuFEx hub for the efficient syntheses of sulfinamides and sulfinate esters

Herein, we demonstrate a method for the syntheses of sulfinamides and sulfinate esters using a novel sulfur(IV) fluoride exchange reaction with organometallic reagents. Our strategy involves the addition of an amine or alcohol nucleophile to thionyl fluoride, acting as a S(IV) SuFEx hub, followed by an organometallic reagent. This approach allows efficient access to sulfinamides (45-91% yields) and sulfinate esters (44-82% yields) in only 30 minutes. The sulfinamide and sulfinate esters also can be readily derivatized to the corresponding S(VI) sulfonamides, sulfonate esters, sulfonimidamides, and sulfonimidates without isolation of the intermediates.

Design of Stable Chiral Aminosulfonium Ylides and Their Catalytic Asymmetric Synthesis

The isolation and catalytic enantioselective synthesis of configurationally stable S-stereogenic sulfonium ylides have been significant challenges in the field of asymmetric synthesis. These reactive intermediates are crucial for a variety of synthetic transformations, yet their inherent tendency towards rapid inversion at the sulfur stereocenter has hindered their practical utilization. Conventional approaches have focused on strategies that incorporate a C=S bond-containing cyclic framework to help mitigate this stereochemical lability. In this work, we present an alternative tactic that leverages the stabilizing influence of an adjacent N-atom and cyclic sulfide moiety. Exploiting a copper catalyzed enantioselective intermolecular carbene transfer reaction, structurally diverse S-stereogenic aminosulfonium ylides have been achieved in excellent yields and enantioselectivities. Experimental results indicate that the careful selection of 2-diazo-1,3-diketone precursors is crucial for achieving optimal stereoinduction in this transformation. The resulting highly enantioenriched aminosulfonium ylides allow for further stereospecific elaborations to furnish aminosulfonium ylide oxides and sulfinamide. This work expands the boundaries of chiral sulfonium ylide chemistry, providing access to a broad range of previously elusive S-stereogenic aminosulfonium ylide scaffolds.

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.

Modular synthesis of α-branched secondary alkylamines via visible-light-mediated carbonyl alkylative amination

The development of methods for the assembly of secondary α-alkyl amines remains a central challenge to chemical synthesis because of their critical importance in modulating the physical properties of biologically active molecules. Despite decades of intensive research, chemists still rely on selective N-alkylation and carbonyl reductive amination to make most amine products. Here we report the further evolution of a carbonyl alkylative amination process that, for the first time, brings together primary amines, aldehydes and alkyl iodides in a visible-light-mediated multicomponent coupling reaction for the synthesis of a wide range of α-branched secondary alkylamines. In addition to exploring the tolerance and limitations in each reaction component, we also report preliminary applications to the telescoped synthesis of α-branched N-heterocycles and an N-alkylation protocol that is selective for primary over cyclic secondary amines. Our data support a mechanism involving addition of an alkyl radical to an uncharged alkyl imine which, to the best of our knowledge, has not previously been described. We believe that this method will enable practitioners of synthetic chemistry in academic and industrial settings to approach the synthesis of these important molecules in a manner that is streamlined compared to established approaches.

Zirconium Hydride Catalysis Initiated by Tetrabutylammonium Fluoride

In our drug discovery campaigns to target the oncogenic drivers of cancers, the demand for a chemoselective, stereoselective and economical synthesis of chiral benzylamines drove the development of a catalytic zirconium hydride reduction. This methodology uses the inexpensive, bench stable zirconocene dichloride, and a novel tetrabutylammonium fluoride activation tactic to catalytically generate a metal hydride under ambient conditions. The diastereo- and chemoselectivity of this reaction was tested with the preparation of key intermediates from our discovery programs and in the scope of sulfinyl ketimines and carbonyls relevant to medicinal chemistry and natural product synthesis. A preliminary mechanistic investigation conducted into the role of tetrabutylammonium fluoride indicates that formation of a zirconocene fluoride occurs to initiate catalysis. The implications of this convenient activation approach may provide expanded roles for zirconium hydrides in catalytic transformations.

Asymmetric Construction of Ethenyl-Substituted Acyclic Quaternary Stereocenters at the α-Position of Carbonyl Surrogates via Stereoselective Sulfonylvinylation-Reductive Desulfonylation

N-Sulfinyl metalloenamines, derived from geometry-defined β,β-disubstituted enesulfinamides, undergo conjugate addition-elimination reaction with β-tosyl nitroolefin to afford α-sulfonylvinylated ketimines with high stereocontrol. Further desulfonylation using sodium naphthalenide gives carbonyl surrogates bearing a less-accessible acyclic quaternary α-stereocenters substituted with an ethenyl group and two sterically and electronically similar groups (e.g., methyl and ethyl). Synthetic application of the described protocol was demonstrated by enantioselective synthesis of (S)-bakuchiol.

Zinc Promoted Cross-Electrophile Sulfonylation to Access Alkyl-Alkyl Sulfones

The transition metal-catalyzed multi-component cross-electrophile sulfonylation, which incorporates SO2 as a linker within organic frameworks, has proven to be a powerful, efficient, and cost-effective means of synthesizing challenging alkyl-alkyl sulfones. Transition metal catalysts play a crucial role in this method by transferring electrons from reductants to electrophilic organohalides, thereby causing undesirable side reactions such as homocoupling, protodehalogenation, β-hydride elimination, etc. It is worth noting that tertiary alkyl halides have rarely been demonstrated to be compatible with current methods owing to various undesired side reactions. In this work, a zinc-promoted cross-electrophile sulfonylation is developed through a radical-polar crossover pathway. This approach enables the synthesis of various alkyl-alkyl sulfones, including 1°-1°, 2°-1°, 3°-1°, 2°-2°, and 3°-2° types, from inexpensive and readily available alkyl halides. Various functional groups are well tolerated in the work, resulting in yields of up to 93%. Additionally, this protocol has been successfully applied to intramolecular sulfonylation and homo-sulfonylation reactions. The insights gained from this work shall be useful for the further development of cross-electrophile sulfonylation to access alkyl-alkyl sulfones.

Enantioselective construction of stereogenic-at-sulfur(IV) centres via catalytic acyl transfer sulfinylation

Chiral sulfur pharmacophores are crucial for drug discovery in bioscience and medicinal chemistry. While the catalytic asymmetric synthesis of sulfoxides and sulfinate esters with stereogenic-at-sulfur(IV) centres is well developed, the synthesis of chiral sulfinamides remains challenging, which has primarily been attributed to the high nucleophilicity and competing reactions of amines. In this study, we have developed an efficient methodology for the catalytic asymmetric synthesis of chiral sulfinamides and sulfinate esters by the sulfinylation of diverse nucleophiles, including aromatic amines and alcohols, using our bifunctional chiral 4-arylpyridine N-oxides as catalysts. The remarkable results are a testament to the efficiency, versatility and broad applicability of the developed synthetic approach, serving as a valuable tool for the synthesis of sulfur pharmacophores. Mechanistic experiments and density functional theory calculations revealed that the initiation and stereocontrol of this reaction are induced by an acyl transfer catalyst. Our research provides an efficient approach for the construction of optically pure sulfur(IV) centres.

Design, synthesis and evaluation of bioactivity of peptidomimetics based on chloroalkene dipeptide isosteres

Ample biologically active peptides have been found, identified and modified for use in drug discovery to date. However, several factors, such as low metabolic stability due to proteolysis and non-specific interactions with multiple off-target molecules, might limit the therapeutic use of peptides. To enhance the stability and/or bioactivity of peptides, the development of "peptidomimetics," which mimick peptide molecules, is considered to be idealistic. Hence, chloroalkene dipeptide isosteres (CADIs) was designed, and their synthetic methods have been developed by us. Briefly, in a CADI an amide bond in peptides is replaced with a chloroalkene structure. CADIs might be superior mimetics of amide bonds because the Van der Waals radii (VDR) and the electronegativity value of a chlorine atom are close to those of the replaced oxygen atom. By a developed method of the "liner synthesis", N-tert-butylsulfonyl protected CADIs can be synthesized via a key reaction involving diastereoselective allylic alkylation using organocopper reagents. On the other hand, by a developed method of the "convergent synthesis", N-fluorenylmethoxycarbonyl (Fmoc)-protected carboxylic acids can be also constructed based on N- and C-terminal analogues from corresponding amino acid starting materials via an Evans syn aldol reaction and the Ichikawa allylcyanate rearrangement reaction involving a [3.3] sigmatropic rearrangement. Notably, CADIs can also be applied for Fmoc-based solid-phase peptide synthesis and therefore introduced into bioactive peptides including as the Arg-Gly-Asp (RGD) peptide and the amyloid β fragment Lys-Leu-Val-Phe-Phe (KLVFF) peptide, which are correlated with cell attachment and Alzheimer's disease (AD), respectively. These CADI-containing peptidomimetics stabilized the conformation and enhanced the potency of the cyclic RGD peptide and the cyclic KLVFF peptide.

Rh(II)-Catalyzed Enantioselective S-Alkylation of Sulfenamides with Acceptor-Acceptor Diazo Compounds Enables the Synthesis of Sulfoximines Displaying Diverse Functionality

The Rh(II)-catalyzed enantioselective S-alkylation of sulfenamides with α-amide diazoacetates at 1 mol % catalyst loading to obtain sulfilimines in high yields and enantiomeric ratios of up to 99:1 is reported. The enantioenriched sulfilimine products incorporate versatile amide functionality poised for further elaboration to diverse sulfoximines with multiple stereogenic centers, including by highly diastereoselective sulfilimine and sulfoximine α-alkylation with alkylating agents and epoxides and by interconversion of the amide to N-tert-butanesulfinyl aldimines, followed by diastereoselective additions.

Palladium-Catalyzed Addition of Aryl Halides to N-Sulfinylamines for the Synthesis of Sulfinamides

Sulfinamides are versatile, synthetically useful intermediates, and final motifs. Traditional methods to synthesize sulfinamides generally require substrates with preinstalled sulfur centers. However, these precursors have limited commercial availability, and the associated synthetic routes often require harsh reaction conditions and highly reactive reagents, thus severely limiting their application. Herein, we report the synthesis of sulfinamides from aryl and alkenyl (pseudo)halides and N-sulfinylamines, enabled by palladium catalysis. The reactions use mild conditions and are achieved without the use of highly reactive preformed organometallic reagents, resulting in transformations of broad generality and high functional group tolerance. In particular, substrates featuring protic and electrophilic functional groups can be used successfully. The modification of complex aryl cores and natural product derivatives demonstrates the utility of this method.

Asymmetric 1,2-Migration at Vicinal Tetrasubstituted Stereocenters Constructed from α-Keto Imines

A carbonyl-assisted asymmetric 1,2-migratory allylation through in situ generation of vicinal tetrasubstituted stereocenters is reported to access enantiopure α-amino ketones and amino alcohols with excellent yields and diastereoselectivities. In a remarkable divergence, despite higher steric hindrance, the allylation exclusively occurs on ketones over imines in the first step, followed by a face-selective 1,2-allyl transfer, thus highlighting an exciting interplay between two distinct electrophiles. The methodology distinguishes itself through its adaptability to gram-scale synthesis, showcasing broad functional-group tolerance and stereodivergence. Density functional theory (DFT) analysis led to a deeper understanding of its selectivity and mechanistic framework. Highlighting its transformative potential, the method was applied to the total synthesis of hapalindole alkaloids.

Stereoselective Electrophilic Sulfenylation of β,β-Disubstituted Enesulfinamides: Asymmetric Construction of Less Accessible Acyclic α,α-Disubstituted α-Sulfenylated Ketimines

Current methods for the asymmetric α-sulfenylation of carbonyls cannot be applied to acyclic carbonyls that have two similar substituents at the α-position. This research demonstrated that the electrophilic sulfenylation of geometry-defined acyclic β,β-disubstituted enesulfinamides using S-aryl or S-alkyl benzenethiosulfonates can be highly stereoselective. This process results in enantioenriched α,α-disubstituted α-sulfenylated ketone surrogates with sulfur-containing acyclic tetrasubstituted carbon stereocenters bearing two electronically and sterically similar substituents (e.g., methyl and ethyl). Furthermore, by employing the corresponding stereoisomers of enensulfinamides, any of the four stereoisomers of α-sulfenylated ketimines can be selectively accessed.

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.

Catalytic Asymmetric Synthesis of Sulfinamides via Cu-Catalyzed Asymmetric Addition of Aryl Boroxines to Sulfinylamines

The application of sulfinamides has been witnessed in medicinal and agrochemistry with employment in asymmetric transformations. However, methods for their asymmetric catalytic synthesis have rarely been explored. Herein, the catalytic enantioselective addition of aryl boroxines to sulfinylamines via Cu catalyst and the newly developed Xuphos ligand were reported. A series of chiral aryl sulfinamides can be readily accessed in one step. This protocol enables the stereospecific transformation of sulfinamides to sulfonimidoyl fluorides, sulfonimidamides, and sulfonimidate esters. DFT calculations have revealed the reaction pathway, and the migratory insertion is the enantio-determining step. The noncovalent interaction between the oxygen atom of sulfinylamines and the C-H bonds in the ligand is crucial for enantioselectivity control.

Amine adducts of triallylborane as highly reactive allylborating agents for Cu(I)-catalyzed allylation of chiral sulfinylimines

The implementation of selective catalytic processes with highly active reagents is an attractive strategy that meets the modern principles of sustainable development of chemistry. In the current study, we for the first time describe the method and general principles of Cu(I)-catalyzed allylation of imines with amine adducts of allylic triorganoboranes. Triallylborane is an extremely reactive compound and cannot be used for the catalytic allylation of imines, whereas its amine adducts are ideal substrates for catalysis. The structure of the amine fragment successfully balances the safety, selectivity and stability of the allylboron reagent, allowing it to demonstrate high activity in catalytic allylation reactions, exceeding many times any known allylboranes. The obtained results are supported by quantitative kinetics data and DFT calculations. The catalytic efficacy of the system was demonstrated on model sulfinylimines (23 examples). High diastereoselectivity up to >99% was achieved, including for the gram-scale synthesis of 2-hydroxyphenyl-derivatives. Taking into account the high reactivity and unsurpassed atom-economy of amine adducts of triallylborane (AAT), they can be considered as prospective allylation reagents with Cu(I) and other appropriate metallocatalysts.

Stereoselective Construction of Less-Accessible Acyclic α,α-Disubstituted β-Ketiminonitriles via Electrophilic Cyanation of β,β-Disubstituted Enesulfinamides

The metalloenamines, formed by NH-deprotonation of β,β-disubstituted enesulfinamides, can undergo reactions with commercially available electrophilic cyanating reagents such as tosyl cyanide (TsCN) or 3-oxo-1,2-benziodoxole-1(3H)-carbonitrile (CBX). Through the utilization of appropriate stereoisomers of enesulfinamides, this method enables the selective synthesis of any of the four stereoisomers of α,α-disubstituted β-sulfinylimino nitriles, which feature acyclic quaternary stereocenters and are typically more challenging to synthesize. These compounds can then undergo stereoselective nucleophilic addition, leading to the creation of valuable enantioenriched multisubstituted β-amino carbonyl surrogates with a high degree of structural diversity.

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.

Design and Asymmetric Control of Orientational Chirality by Using the Combination of C(sp2)-C(sp) Levers and Achiral N-Protecting Group

New chiral targets of orientational chirality have been designed and asymmetrically synthesized by taking advantage of N-sulfinyl imine-directed nucleophilic addition/oxidation, Suzuki-Miyaura, and Sonogashira cross-coupling reactions. Orientation of single isomers has been selectively controlled by using aryl/alkynyl levers [C(sp2)-C(sp) axis] and tBuSO2- protecting group on nitrogen as proven by X-ray diffraction analysis. The key structural characteristic of resulting orientational products is shown by remote through-space blocking manner. Seventeen examples of multi-step synthesis were obtained with modest to good chemical yields and complete orientational selectivity.