Diversity Oriented Clicking (DOC): Divergent Synthesis of SuFExable Pharmacophores from 2-Substituted-Alkynyl-1-Sulfonyl Fluoride (SASF) Hubs

Diversity Oriented Clicking (DOC) is a unified click-approach for the modular synthesis of lead-like structures through application of the wide family of click transformations. DOC evolved from the concept of achieving “diversity with ease”, by combining classic C−C π-bond click chemistry with recent developments in connective SuFEx-technologies. We showcase 2-S ubstituted-A lkynyl-1-S ulfonyl F luorides (SASFs) as a new class of connective hub in concert with a diverse selection of click-cycloaddition processes. Through the selective DOC of SASFs with a range of dipoles and cyclic dienes, we report a diverse click-library of 173 unique functional molecules in minimal synthetic steps. The SuFExable library comprises 10 discrete heterocyclic core structures derived from 1,3- and 1,5-dipoles; while reaction with cyclic dienes yields several three-dimensional bicyclic Diels–Alder adducts. Growing the library to 278 discrete compounds through late-stage modification was made possible through SuFEx click derivatization of the pendant sulfonyl fluoride group in 96 well-plates—demonstrating the versatility of the DOC approach for the rapid synthesis of diverse functional structures. Screening for function against MRSA (USA300) revealed several lead hits with improved activity over methicillin.     

Cu‐free Sonogashira Type Cross‐Coupling of 6‐Halo‐2‐cyclopropyl‐3‐(pyridyl‐3‐ylmethyl) Quinazolin‐4(3H)‐ones as Potential Antimicrobial Agents

C(sp)–C(sp2) bond formation via Sonogashira cross‐coupling reactions on 6‐halo‐2‐cyclopropyl‐3‐(pyridyl‐3‐ylmethyl)quinazolin‐4(3H )‐ones with appropriate alkynes was explored. Optimization of reaction conditions with various catalysts, ligands, bases, and solvents was conducted. The combination of PdCl₂(MeCN)₂ with X‐Phos proved to be the best metal–ligand system for this conversion in the presence of triethylamine (Et₃N) in tetrahydrofuran at room temperature for iodosubstrates, at 80°C for the bromosubstrates in 8 h, and also for the chlorosubstrates in 16 h. We also demonstrated synthesis of a successful diversity‐oriented synthesis library of highly functionalized quinazolinones via Cu‐free Sonogashira coupling of diverse aryl halides and azido‐alkyne (“click”) ligation reactions with substituted azides. The library exhibited significant antimicrobial activity when screened against several microorganisms.     

Biocompatible SuFEx Click Chemistry: Thionyl Tetrafluoride (SOF4)‐Derived Connective Hubs for Bioconjugation to DNA and Proteins

We report here the development of a suite of biocompatible SuFEx transformations from the SOF₄‐derived iminosulfur oxydifluoride hub in aqueous buffer conditions. These biocompatible SuFEx reactions of iminosulfur oxydifluorides (R‐N=SOF₂) with primary amines give sulfamides (8 examples, up to 98 %), while the reaction with secondary amines furnish sulfuramidimidoyl fluoride products (8 examples, up to 97 %). Likewise, under mild buffered conditions, phenols react with the iminosulfur oxydifluorides (Ar‐N=SOF₂) to produce sulfurofluoridoimidates (13 examples, up to 99 %), which can themselves be further modified by nucleophiles. These transformations open the potential for asymmetric and trisubstituted linkages projecting from the sulfur(VI) center, including versatile S?N and S?O connectivity (9 examples, up to 94 %). Finally, the SuFEx bioconjugation of iminosulfur oxydifluorides to amine‐tagged single‐stranded DNA and to BSA protein demonstrate the potential of SOF₄‐derived SuFEx click chemistry in biological applications.     

Bifluoride Ion Mediated SuFEx Trifluoromethylation of Sulfonyl Fluorides and Iminosulfur Oxydifluorides

SuFEx is a new‐generation click chemistry transformation that exploits the unique properties of S?F bonds and their ability to undergo near‐perfect reactions with nucleophiles. We report here the first SuFEx‐based procedure for the efficient synthesis of pharmaceutically important triflones and bis(trifluoromethyl)sulfur oxyimines from sulfonyl fluorides and iminosulfur oxydifluorides, respectively. The new process involves rapid S?F exchange with trifluoromethyltrimethylsilane (TMSCF₃) upon activation by potassium bifluoride in anhydrous DMSO. The reaction tolerates a wide selection of substrates and proceeds under mild conditions without need for chromatographic purification. A tentative mechanism is proposed involving nucleophilic displacement of S?F by the trifluoromethyl anion via a five‐coordinate intermediate. The utility of late‐stage SuFEx trifluoromethylation is demonstrated through the synthesis and selective anticancer properties of a bis(trifluoromethyl)sulfur oxyimine.     

Copper(I)‐Catalyzed Interrupted Click Reaction: Synthesis of Diverse 5‐Hetero‐Functionalized Triazoles

The 5‐heterofunctionalized triazoles are important scaffolds in bioactive compounds, but current click reactions (CuAAC) cannot produce these core structures. A copper(I)‐catalyzed interrupted click reaction to access diverse 5‐functionalized triazoles is reported. Various 5‐amino‐, thio‐, and selenotriazoles were readily assembled in one step in high yields. The reaction proceeds under mild conditions with complete regioselectivity. It also features a broad substrate scope and good functional group compatibility.     

SuFEx Chemistry of Thionyl Tetrafluoride (SOF4) with Organolithium Nucleophiles: Synthesis of Sulfonimidoyl Fluorides,Sulfoximines, Sulfonimidamides,and Sulfonimidates

Thionyl tetrafluoride (SOF₄) is a valuable connective gas for sulfur fluoride exchange (SuFEx) click chemistry that enables multidimensional linkages to be created via sulfur–oxygen and sulfur–nitrogen bonds. Herein, we expand the available SuFEx chemistry of SOF₄ to include organolithium nucleophiles, and demonstrate, for the first time, the controlled projection of sulfur–carbon links at the sulfur center of SOF₄‐derived iminosulfur oxydifluorides (R¹−N=SOF₂). This method provides rapid and modular access to sulfonimidoyl fluorides (R¹−N=SOFR²), another array of versatile SuFEx connectors with readily tunable reactivity of the S−F handle. Divergent connections derived from these valuable sulfonimidoyl fluoride units are also demonstrated, including the synthesis of sulfoximines, sulfonimidamides, and sulfonimidates.     

Synthesis of Purine‐based Triazoles by Copper (I)‐catalyzed Huisgen Azide–Alkyne Cycloaddition Reaction

An efficient protocol for the synthesis of substituted 1,2,3‐triazol‐9H‐purines via copper (I)‐catalyzed click chemistry of 2,6‐dichloropurine with aromatic azide has been reported. A wide range of 1,4‐disubstituted triazoles ( N‐9 substituted purines) was accessible in good‐to‐excellent yields with remarkable functional group tolerance. The base‐catalyst ratio was tuned to achieve optimum reaction condition (>95% conversion and purity in most cases). Furthermore, the structure of 4i has been unambiguously assigned by X‐ray crystallographic study to yield structural information on the 1,3‐dipoles entering the reaction.     

SuFEx Chemistry of Thionyl Tetrafluoride (SOF4) with Organolithium Nucleophiles: Synthesis of Sulfonimidoyl Fluorides,Sulfoximines, Sulfonimidamides,and Sulfonimidates

Thionyl tetrafluoride (SOF₄) is a valuable connective gas for sulfur fluoride exchange (SuFEx) click chemistry that enables multidimensional linkages to be created via sulfur–oxygen and sulfur–nitrogen bonds. Herein, we expand the available SuFEx chemistry of SOF₄ to include organolithium nucleophiles, and demonstrate, for the first time, the controlled projection of sulfur–carbon links at the sulfur center of SOF₄‐derived iminosulfur oxydifluorides (R¹?N=SOF₂). This method provides rapid and modular access to sulfonimidoyl fluorides (R¹?N=SOFR²), another array of versatile SuFEx connectors with readily tunable reactivity of the S?F handle. Divergent connections derived from these valuable sulfonimidoyl fluoride units are also demonstrated, including the synthesis of sulfoximines, sulfonimidamides, and sulfonimidates.     

Ethene-1,1-disulfonyl Difluoride (EDSF) for SuFEx Click Chemistry: Synthesis of SuFExable 1,1-Bissulfonylfluoride Substituted Cyclobutene Hubs

We present the synthesis of 1,1-bis(fluorosulfonyl)-2-(pyridin-1-ium-1-yl)ethan-1-ide, a bench-stable precursor to ethene-1,1-disulfonyl difluoride (EDSF). The novel SuFEx reagent, EDSF, is demonstrated in the preparation of 26 unique 1,1-bissulfonylfluoride substituted cyclobutenes via a cycloaddition reaction. The regioselective click cycloaddition reaction is rapid, straightforward, and highly efficient, enabling the generation of highly functionalized 4-membered ring (4MR) carbocycles. These carbocycles are valuable structural motifs found in numerous bioactive natural products and pharmaceutically relevant small molecules. Additionally, we showcase diversification of the novel cyclobutene cores through selective Cs₂CO₃-activated SuFEx click chemistry between a single S−F group and an aryl alcohol, yielding the corresponding sulfonate ester products with high efficiency. Finally, density functional theory calculations offer mechanistic insights about the reaction pathway.     

1,2,3-三唑取代的1,4-二氢-4-氧代-1,5-二氮杂萘-3-羧酸衍生物的设计、合成与HIV整合酶抑制活性评价

一价铜催化端炔与叠氮化物的1, 3-环加成反应是一种快速构建小分子库并筛选其可能性质的的主要方法。本文报道了1,2,3-三唑取代的1,4-二氢-4-氧代-1,5-二氮杂萘-3-羧酸衍生物的设计与合成。在该类化合物中,疏水性与亲水性片段通过Click反应有效地连接。所设计化合物8和12的结构通过光谱手段进行了表征;其可能的HIV整合酶抑制活性也进行了筛选。     

Construction of a combinatorial library of 2‐(4‐oxo‐4H‐1‐benzopyran‐3‐yl)‐4‐thiazolidinones by microwave‐assisted one‐pot parallel syntheses

A one‐pot liquid‐phase combinatorial synthesis of 2‐(4‐oxo‐4H‐1‐benzopyran‐3‐yl)‐4‐thiazolidinones bearing diverse substituents at the 3‐position under microwave irradiation was successfully performed using 3‐formyl chromone, primary amine, and mercaptoacetic acid as reactants. Compared to an identical library generated by conventional parallel synthesis, the microwave‐assisted parallel synthesis approach dramatically decreased the reaction time from an average of 9 h to 5 min, and substantially increased the product yields. The coupling of microwave technology with liquid‐phase combinatorial synthesis constitutes a novel and particularly attractive avenue for the rapid generation of structurally diverse libraries. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:381–389, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20309     

cis‐1,4‐specific carbocationic polymerization and copolymerization of 1,3‐dienes initiated by (S,S)‐bis(oxazolinylphenyl)amine chromium complexes

Two new chiral (S,S)‐bis(oxazolinylphenyl)amine chromium dichloride complexes have been synthesized and structurally characterized. In combination with 2 equiv. of borate and an excess of AlR₃, such Cr complexes serve as effective cationic initiators in the stereoregular carbocationic polymerization of 1,3‐dienes such as isoprene (IP) and myrcene (MY), affording cyclized cis‐1,4‐PIPs/PMys (cis‐1,4‐selectivity up to 96%) with cyclic sequence contents ranging from 26% to 87%. Moreover, these Cr initiator systems also exhibit an unprecedented control over sequence distribution of comonomers in the carbocationic copolymerization of IP and MY, preparing novel copolymers with different microstructures from mainly cyclized cis‐1,4‐specific statistical copolymers to cyclic olefin copolymers. The nature of Cr complex, borate, AlR₃, temperature, molar ratio of comonomers has considerable effect on the (co)polymer's yield, stereoselectivity, cyclization, and comonomer sequence distribution. A plausible mechanism is suggested, which gives a new strategy for biomimetic synthesis of natural rubber. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 55, 1250–1259     

Functional Polythioamides Derived from Thiocarbonyl Fluoride**

Polythioamide is a unique type of sulfur-containing polymer with advanced functionalities. Nonetheless, the elemental sulfur commonly used in their synthesis tends to react readily with unsaturated functional groups, thereby limiting the scope of eligible substrates. Inspired by the highly efficient sulfur-fluoride exchange ( SuFEx ) polymerization through discrete hubs, we present herein a pioneering and versatile approach to the synthesis of polythioamides from diboronic acids, secondary diamines, and thiocarbonyl fluoride as the central connective hub. Well-defined structures, including previously inaccessible unsaturated substrates, were realized. These newly devised polythioamides can efficiently and selectively bind to metal ions and were applied in precious-metal recovery. Further development resulted in Pd^II-crosslinked single-chain nanoparticles serving as recyclable homogeneous catalysts, thus demonstrating the vast potential of these unprecedented polythioamides. We anticipate that thiocarbonyl fluoride could emerge as a potent hub for facilitating the intricate synthesis of sulfur-containing polymers.     

Silicon‐Free SuFEx Reactions of Sulfonimidoyl Fluorides: Scope,Enantioselectivity, and Mechanism

SuFEx reactions, in which an S?F moiety reacts with a silyl‐protected phenol, have been developed as powerful click reactions. In the current paper we open up the potential of SuFEx reactions as enantioselective reactions, analyze the role of Si and outline the mechanism of this reaction. As a result, fast, high‐yielding, “Si‐free” and enantiospecific SuFEx reactions of sulfonimidoyl fluorides have been developed, and their mechanism shown, by both experimental and theoretical methods, to yield chiral products.     

A Copper‐Catalyzed Multicomponent Reaction and ‘Click Strategy’ for the Stereoselective Synthesis of a New Series of Oxazolone Peptidomimetics with α‐Acylamino Amide and β‐Amido Ketone Structures

A novel ‘click ligation’ strategy for the stereoselective synthesis of a medium‐size library of structurally complex and functionally diverse oxazolone peptidomimetics, which contain α‐acylamino carboxamide or β‐amido ketone residues, is presented. Most of these molecules have lipophilicity constant values (log P) in the qualifying range for cell permeability, and that indicates the possibilities of these new molecules to be used in the search for potential inhibitors for a broad spectrum of enzymes.     

Copper(I)‐Catalyzed Interrupted Click/Sulfenylation Cascade: One‐Pot Synthesis of Sulfur Cycle Fused 1,2,3‐Triazoles

Herein, we report a practical protocol for the synthesis of sulfur cycle fused 1,2,3‐triazoles through a copper(I)‐catalyzed tandem click/intramolecular sulfenylation reaction. The reaction proceeded via a copper‐catalyzed alkyne azide cycloaddition, followed by interception of the in situ formed cuprate‐triazole intermediate with p‐toluenesulfonothioate. This reaction shows broad substrate scope, complete regioselectivity, and excellent functional group tolerance under mild reaction conditions.     

SuFEx on the Surface: A Flexible Platform for Postpolymerization Modification of Polymer Brushes

Polymer brushes present a unique architecture for tailoring surface functionalities due to their distinctive physicochemical properties. However, the polymerization chemistries used to grow brushes place limitations on the monomers that can be grown directly from the surface. Several forms of click chemistry have previously been used to modify polymer brushes by postpolymerization modification with high efficiency, however, it is usually difficult to include the unprotected moieties in the original monomer. We present the use of a new form of click chemistry known as SuFEx (sulfur(VI) fluoride exchange), which allows a silyl ether to be rapidly and quantitatively clicked to a polymer brush grown by free‐radical polymerization containing native ‐SO₂F groups with rapid pseudo‐first‐order rates as high as 0.04 s^?1. Furthermore, we demonstrate the use of SuFEx to facilely add a variety of other chemical functional groups to brush substrates that have highly useful and orthogonal reactivity, including alkynes, thiols, and dienes.     

A Heck–Matsuda Process for the Synthesis of β‐Arylethenesulfonyl Fluorides: Selectively Addressable Bis‐electrophiles for SuFEx Click Chemistry

A Heck–Matsuda process for the synthesis of the otherwise difficult to access compounds, β‐arylethenesulfonyl fluorides, is described. Ethenesulfonyl fluoride (i.e., vinylsulfonyl fluoride, or ESF) undergoes β‐arylation with stable and readily prepared arenediazonium tetrafluoroborates in the presence of the catalyst palladium(II) acetate to afford the E‐isomer sulfonyl analogues of cinnamoyl fluoride in 43–97 % yield. The β‐arylethenesulfonyl fluorides are found to be selectively addressable bis‐electrophiles for sulfur(VI) fluoride exchange (SuFEx) click chemistry, in which either the alkenyl moiety or the sulfonyl fluoride group can be the exclusive site of nucleophilic attack under defined conditions, making these rather simple cores attractive for covalent drug discovery.     

Transition‐Metal‐Free Cross‐Coupling of Benzothiophenes and Styrenes in a Stereoselective Synthesis of Substituted (E,Z)‐1,3‐Dienes

A transition metal‐free one‐pot stereoselective approach to substituted (E,Z)‐1,3‐dienes was developed by using an interrupted Pummerer reaction/ligand‐coupling strategy. Readily available benzothiophene S‐oxides, which can be conveniently prepared by oxidation of the parent benzothiophenes, undergo Pummerer coupling with styrenes. Reaction of the resultant sulfonium salts with alkyllithium/magnesium reagents generates underexploited hypervalent sulfurane intermediates that undergo selective ligand coupling, resulting in dismantling of the benzothiophene motif and the formation of decorated (E,Z)‐1,3‐dienes.