Steric Nature Research Articles

Elucidating the mechanisms of the molecular sieving phenomenon created by comb-shaped polymers grafted to a protein – a simulation study

Advances in polymer chemistry now allow the creation of protein–polymer conjugates of great complexity. These advances equally enable the fine-tuning of their structure (and hence properties) to address specific challenges they face as therapeutics. Some of these challenges faced by non-human proteins include their rapid degradation, elimination or immunogenicity in vivo, and one of the most recognized solutions for this is to mask their surface with chains of linear poly(ethylene glycol). This, however, generally reduces bioactivity. Several experimental studies have shown that switching from linear to architecturally complex polymers (comb-shaped, branched, dendronized) partially resolves this issue for a subset of proteins whose bioactivity involves small molecules, by creating a “molecular sieving” effect. The mechanisms underlying molecular sieving, however, have never been entirely elucidated. This study presents a coarse-grained model of α-chymotrypsin modified with multiple chains of the comb-shaped polymer poly(oligo(ethylene glycol) methyl ether methacrylate) to study molecular sieving. Results demonstrate the steric nature of the phenomenon (i.e., creation of gaps in the polymer coating), though steric considerations alone could not reconcile all of the experimental trends. The simulations rather suggest that these gaps enable the selective accumulation of small (substrate) molecules near the surface of the protein (in a favourable microenvironment created by the polymer), which exacerbates the “molecular sieving” phenomenon (i.e., difference in the ability of small vs. large substrates to reach the protein).

Modular Ni(0)/Silane Catalytic System for the Isomerization of Alkenes

Alkenes are used ubiquitously as starting materials and synthetic targets in all areas of chemistry. Controlling their geometry and position along a chain is vital to their reactivity and properties yet remains challenging. Alkene isomerization is an atom-economical process to synthesize targeted alkenes, and selectivity can be controlled using transition metal catalysts. The development of mild, selective isomerization reactivity has enabled efficient tandem catalytic systems for the remote functionalization of alkenes, a process in which a starting alkene is isomerized to a new position prior to the functionalization step. The key challenges in developing isomerization catalysts for remote functionalization applications are (i) a lack of modularity in the catalyst structure and (ii) the requirement of nonmodular and/or harsh additives during catalyst activation. We address both challenges with a modular (NHC)Ni(0)/silane catalytic system (NHC, N-heterocyclic carbene), demonstrating the use of triaryl silanes and readily accessible (NHC)Ni(0) complexes to form the proposed active (NHC)(silyl)Ni–H species in situ. We show that modification of the steric and electronic nature of the catalyst via modification of the ancillary ligand and silane partner, respectively, is easily achieved, creating a uniquely versatile catalytic system that is effective for the formation of internal alkenes with high yield and selectivity for the E-alkene. The use of silanes as mild activators enables isomerization of substrates with a variety of functional groups, including acid-labile groups. The broad substrate scope, enabled by catalyst design, makes this catalytic system a strong candidate for use in tandem catalytic applications. Preliminary mechanistic studies support a Ni–H insertion/elimination pathway.

Hybrid cycloolefin ligands for palladium–olefin cooperative catalysis

The engineering of molecular catalysts in homogeneous catalysis enables new catalytic modes, which leads to efficient synthetic transformations. In this regard, the design of ligands for transition metal catalysis has played a major role. In transition metal catalysed reactions, olefins can serve as steering ligands by tuning the electronic and steric nature of the metal centre. Here we report unstrained olefin ligands that bear a P or S coordination site for use in the Pd-catalysed Catellani reaction. This olefin ligand shows a covalent catalytic function and enables an efficient ipso,ortho-difunctionalization of iodoarenes. Mechanistic analysis reveals a reversible covalent bonding between the substrate and the cycloolefin unit of the ligand, which forms key organopalladium intermediates to enable a new reactivity. Our results demonstrate a design concept that employs hybrid cycloolefin ligands as a covalent catalytic module, which opens up possibilities for further cooperative catalysis with other transition metal–olefin hybrids. Taking inspiration from palladium–norbornene cooperative catalysis, Catellani-type reactions are now performed using a hybrid olefin ligand with a P or S coordination site. This olefin ligand enables efficient ipso,ortho-difunctionalization of iodoarenes. Mechanistic studies show the formation of organopalladium intermediates that comprise both the substrate and the hybrid olefin ligand.

Copper(II)-Catalyzed [3+2] Annulation of Thioamides with AIBN: Facile Access to Highly Functionalized Thiazolidin-4-ones

AbstractAn efficient and versatile copper-catalyzed intermolecular radical [3+2] annulation of thioamides with azobisisobutyronitrile (AIBN) is described. This two-component copper(II)-catalyzed transformation is achieved in one pot via cascade formation of C–S/C–N bonds through cyclization of an in situ generated N,S-acetal intermediate derived from a β-ketothioamide. This operationally simple method allows direct access to synthetically demanding thiazolidin-4-ones in good to excellent yields containing diverse functional groups of different electronic and steric nature. The readily available reaction partners, the avoidance of expensive/toxic reagents and a gram-scale synthesis are additional attributes of this strategy. AIBN plays a dual role as a radical initiator and an unusual source of a two-carbon coupling partner. Notably, the products possess Z stereochemistry with regard to the exo­cyclic C=C double bond at position 2 of the thiazolidine ring.

Optimizing bromide anchors for easy tethering of amines, nitriles and thiols in porous organic polymers towards enhanced CO2 capture

Porous organic polymers with labile leaving groups offer direct access to reactive functional groups, otherwise not permissible during network formation. In a one-step, open air, self-coupling reaction of tris bromomethyl benzene, we report highly porous, bromine rich C–C bonded porous polymers. Due to the steric nature of the monomer, restrictive crosslinking allowed pendent bromine groups to remain unreacted and provided rapid exchange into amines, nitriles, and thiols. This simple but powerful strategy yielded two isostructural but varying porosity and pendent group density polymers, allowing a comparative gas uptake study. Despite having lower surface area, the porous polymer formed at low temperature showed higher amination due to higher density of bromine groups. The polymers with more pendant groups resulted better CO 2 uptake performances than higher porosity polymers with less pendant groups. Although post-modification decreased surface area of materials, amine functionalization greatly improved the CO 2 uptake capacity. The ethylenediamine appended version exhibited 4.7 times increase in CO 2 uptake capacity with highest CO 2 /N 2 selectivity of 729 (298 K), and with an isosteric heat of 97 kJ mol −1 at zero coverage. • The one-step synthesis of bromine tethered C–C bonded nanoporous polymers. • The tuning of porosity and number of bromine anchors by changing reaction temperature. • Successful tailoring of benzyl bromides with amine, thiol, and nitrile moieties. • The density of surface functional groups exhibits higher impact on CO 2 adsorption performance than porosity.

Exploring the chemo-, regio-, and stereoselectivities of the (3 + 2) cycloaddition reaction of 5,5-dimethyl-3-methylene-2-pyrrolidinone with C,N-diarylnitrones and nitrile oxide derivatives: a DFT study

The (3 + 2) cycloaddition (32CA) reaction is an efficient method for the synthesis of many biologically active heterocyclic compounds, but there are several regio- and stereochemical issues that must be fully understood to exploit the full utility of its synthetic power. We herein explored the chemo-, regio-, and stereoselectivities of the 32CA reaction of 5,5-dimethyl-3-methylene-2-pyrrolidinone (B1) to C,N-diarylnitrones (B2), and nitrile oxide derivatives (B3) with DFT at the M06/6-311G(d,p) level of theory. The reactions occur via an asynchronous one-step mechanism, with the chemoselective addition of the C,N-diarylnitrones, and nitrile oxide derivatives across the olefinic bond of 5,5-dimethyl-3-methylene-2-pyrrolidinone being the most preferred kinetically and thermodynamically. The regio- and stereoselectivities of the reactions are affected by the electronic and steric nature of substituents on B2 but they are not affected by the electronic and steric nature of substituents on B3. The C,N-nitrones and the nitrile oxide derivatives add across the atomic centers with the largest atomic spin densities on 5,5-dimethyl-3-methylene-2-pyrrolidinone as seen through the local electrophilic ([Formula: see text]) and nucleophilic ([Formula: see text]) Parr functions of the various reaction centers. Results from the global electron density transfer (GEDT) reveal the low polar nature of the reactions.

Influence of Stabilizers on the Performance of Au/TiO2 Catalysts for CO Oxidation

Stabilizers are commonly employed to synthesize nanocrystals with well-defined morphologies and size distributions, making them ideal tools to study structure–activity relationships in heterogeneous catalysts. While it is well documented that stabilizers can influence both the structure and size of the nanocrystals, little emphasis has been placed on how the properties of these species influence catalytic performance. Herein, different polymers (poly-sodium acrylate (PNaA), poly(vinyl alcohol) (PVA), and poly(vinyl pyrrolidone) (PVP)) and the monomer sodium acrylate (NaA) were used as stabilizers for the synthesis of Au nanoparticles supported on TiO2. The mean Au particle size in all of the catalysts was comparable regardless of the stabilizer used; however, the activity of these catalysts toward CO oxidation differed markedly. The activity decreased in the sequence Au/TiO2 (NaA) > Au/TiO2 (PNaA) > Au/TiO2 (none) > Au/TiO2 (PVA) > Au/TiO2 (PVP), despite the Au/TiO2 (none) catalyst possessing a larger Au mean particle size, suggesting active site blocking due to the steric nature of the polymer species. According to UV–vis, X-ray photoelectron spectroscopy (XPS), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), high-resolution transmission electron microscopy (HRTEM), X-ray absorption spectroscopy (XAS), and composition analysis experiments, it was concluded that the enhanced activity of Au/TiO2 (NaA) and Au/TiO2 (PNaA) catalysts were attributed to the large proportions of low coordinate step/kink Au sites. It is to be noted that the electronic interactions between NaA and HAuCl4 facilitated the production of active Au nanoparticles. Our findings highlight that the physicochemical properties of the stabilizer can profoundly influence the reactivity of supported metal catalysts prepared by sol-immobilization. These observations highlight the influence that various stabilizers have on the morphology of supported metal nanoparticles and provides an explanation for the low activity of catalysts prepared using common forms such as PVA and PVP.

Revisiting the Balz-Schiemann Reaction of Aryldiazonium Tetrafluoroborate in Different Solvents under Catalyst- and Additive-Free Conditions.

The thermal and photochemical Balz–Schiemann reaction in commonly used solvents was revisited under catalyst- and additive-free conditions. The study showed that using low- or non-polar solvents could improve the pyrolysis and photolysis of aryldiazonium tetrafluoroborates, enabling effective fluorination at a low temperature or under visible-light irradiation. PhCl and hexane were exemplified as cheap and reliable solvents for both reactions, providing good to excellent yields of aryl fluorides from the corresponding diazonium tetrafluoroborates. The combination of slight heating with visible-light irradiation was beneficial for the transformation of stable aryldiazonium tetrafluoroborates. Nevertheless, the electronic and steric nature of aryldiazonium tetrafluoroborates still had a pivotal effect on both fluorinations even in these solvents.

Quantum chemical investigation of the formation of spiroheterocyclic compounds via the (3 + 2) cycloaddition reaction of 1-methyl-3-(2,2,2-trifluoroethylidene) pyrrolidin-2-one with diazomethane and nitrone derivatives

The chemo-, regio- and stereoselectivities of the formation of spiroheterocycles via the (3 + 2) cycloaddition (32CA) reaction of 1-methyl-3-(2,2,2-trifluoroethylidene) pyrrolidin-2-one (A1) derivatives with diazomethane and nitrone derivative have been studied at the M06–2X/6-311G level of theory. The reactions of diazomethane (A2) and N-methyl-C-phenyl nitrone (A3) derivatives with 1-methyl-3-(2,2,2-trifluoroethylidene)pyrrolidin-2-one derivatives (A1) occurs chemoselectively along the olefinic bond of A1 via an asynchronous one-step mechanism. Substituents on A3 do not affect the selectivity of reaction whereas the electronic and steric nature of the substituent on A2 does. The title reaction proceeds via forward electron density flux (FEDF), where electron density fluxes from the three-atom components to A1. The global electron density transfer (GEDT) values suggest that the 32CA of A1 with diazomethane is a polar reaction while the 32CA reaction of A1 with N-methyl-C-phenyl nitrone is a non-polar reaction, and an inverse relationship has been established between the polar character of the reactions and activation barriers.

N1H- and N1-Substituted Phenylguanidines as α7 Nicotinic Acetylcholine (nACh) Receptor Antagonists: Structure-Activity Relationship Studies.

We previously reported that N-(3-chlorophenyl)guanidine (1) represents a novel α7 nicotinic ACh (nACh) receptor antagonist chemotype. In the present study, a small series of compounds was synthesized with the intent to investigate the structure-activity relationship (SAR). Preliminary data suggested that the N-methyl analog of 1, 2, was several times more potent. Therefore, the chloro group at the aryl 3-position of 1 and its N1-methyl counterpart 2 were replaced with a number of substituents considering the electronic, lipophilic, and steric nature of the substituents. The potencies of the compounds to inhibit acetylcholine (ACh)-induced responses were obtained in Xenopus laevis oocytes expressing human α7 nicotinic ACh receptors (nAChRs) using a two-electrode voltage-clamp assay. We found that the nature of the 3-position substituents had relatively little (i.e., <10-fold) effect on potency, and the presence of an N1-isopropyl substituent was tolerated. Here, we report the first SAR investigation of this novel α7 nAChR antagonist chemotype.

Enantioselective Synthesis of Cyclopropanone Equivalents and Application to the Formation of Chiral β‐Lactams

AbstractCyclopropanone derivatives have long been considered unsustainable synthetic intermediates because of their extreme strain and kinetic instability. Reported here is the enantioselective synthesis of 1‐sulfonylcyclopropanols, as stable yet powerful equivalents of the corresponding cyclopropanone derivatives, by α‐hydroxylation of sulfonylcyclopropanes using a bis(silyl) peroxide as the electrophilic oxygen source. This work constitutes the first general approach to enantioenriched cyclopropanone derivatives. Both the electronic and steric nature of the sulfonyl moiety, which serves as a base‐labile protecting group and confers crystallinity to these cyclopropanone precursors, were found to have a crucial impact on the rate of equilibration to the corresponding cyclopropanone. The utility of these cyclopropanone surrogates is demonstrated in a mild and stereospecific formal [3+1] cycloaddition with simple hydroxylamines, leading to the efficient formation of chiral β‐lactam derivatives.

Enantioselective Synthesis of Cyclopropanone Equivalents and Application to the Formation of Chiral β-Lactams.

Cyclopropanone derivatives have long been considered unsustainable synthetic intermediates because of their extreme strain and kinetic instability. Reported here is the enantioselective synthesis of 1-sulfonylcyclopropanols, as stable yet powerful equivalents of the corresponding cyclopropanone derivatives, by α-hydroxylation of sulfonylcyclopropanes using a bis(silyl) peroxide as the electrophilic oxygen source. This work constitutes the first general approach to enantioenriched cyclopropanone derivatives. Both the electronic and steric nature of the sulfonyl moiety, which serves as a base-labile protecting group and confers crystallinity to these cyclopropanone precursors, were found to have a crucial impact on the rate of equilibration to the corresponding cyclopropanone. The utility of these cyclopropanone surrogates is demonstrated in a mild and stereospecific formal [3+1] cycloaddition with simple hydroxylamines, leading to the efficient formation of chiral β-lactam derivatives.

Evaluation of the Lewis acidity of metal complexes using ESI mass spectrometry

Metal complexes have extensive applications in catalysis, however, the efficient evaluation of Lewis acidity of metal complexes is still a challenge. Herein, we report a method by using electrospray ionization mass spectrometry (ESI-MS) to evaluate the Lewis acidity of metal complexes in the presence of a reference Lewis base, in which the value of the Lewis acidity can be quantized by the bond dissociation energy (BDE) of the resultant Lewis acid-base pairs. Using this method, the Lewis acidity of tetradentate Schiff-base metal complexes (designated as salenMX), a class of common metal complexes in the homogeneous catalysis, was studied in detail. For the salenM(III)X complexes (M = Al, Cr, Fe, Co), the Lewis acidity tendency is Al > Cr > Fe > Co due to a strong affinity between the Al complex and the reference Lewis base while a weak affinity concerning on the Co complex. Additionally, the effect of ligand steric and electronic nature on the Lewis acidity was studied by using Co complex. Furthermore, density functional theory (DFT) was employed to calculate the BDE, which consists with the results obtained from ESI-MS. The ESI-MS method provides a convenient and efficient method for evaluating the Lewis acidity of metal complexes.

Visible-Light Photocatalysis of Eosin Y: HAT and Complementing MS-CPET Strategy to Trifluoromethylation of β-Ketodithioesters with Langlois' Reagent.

A metal- and oxidant-free photoinduced strategy for thioxo sulfur-selective trifluoromethylation of β-ketodithioesters at room temperature is reported. Excellent Z/E-stereoselectivity has been achieved with cheap and viable Langlois' reagent (CF3SO2Na, sodium triflinate) in the presence of eosin Y, which acts as a hydrogen atom transfer (HAT) catalyst. The reaction proceeds via disulfide intermediate disulfanediylbis(3-(alkylthio)-1-phenylprop-2-en-1-one) (a dimer of β-ketodithioester) followed by complementing proton-coupled electron transfer-mediated reverse HAT cycle of eosin Y. This operationally simple and efficient protocol allows direct access to triflinated α-oxoketene dithioacetals in good to excellent yields bearing diverse synthetically useful functional groups of different electronic and steric nature.

Ir-Catalyzed Reversible Acceptorless Dehydrogenation/Hydrogenation of N-Substituted and Unsubstituted Heterocycles Enabled by a Polymer-Cross-Linking Bisphosphine.

The polystyrene-cross-linking bisphosphine ligand PS-DPPBz was effective for the Ir-catalyzed reversible acceptorless dehydrogenation/hydrogenation of N-heterocycles. Notably, this protocol is applicable to the dehydrogenation of N-substituted indoline derivatives with various N-substituents with different electronic and steric natures. A reaction pathway involving oxidative addition of an N-adjacent C(sp3)-H bond to a bisphosphine-coordinated Ir(I) center is proposed for the dehydrogenation of N-substituted substrates.

Preliminary Investigation of the Antibacterial Activity of Antitumor Drug 3-Amino-1,2,4-Benzotriazine-1,4-Dioxide (Tirapazamine) and its Derivatives

The antitumor drug 3-amino-1,2,4-benzotriazine-1,4-dioxide (tirapazamine, TPZ (1)) along with a number of newly synthesized tirapazamine derivatives (TPZs) bearing substitutions at the 3-amine position of TPZ (1) were estimated for their antibacterial activity against representative Gram-negative Escherichia coli (ATCC 25922) and Salmonella enterica (SL 5676), as well as Gram-positive Staphylococcus aureus (ATCC 25923) bacterial strains. Their activities in terms of minimum inhibitory concentrations (MICs) varied in the range of 1.1 µM (0.25 µg/mL)–413 µM (128 µg/mL). Amongst the most potent derivatives (1–6), acetyl- and methoxycarbonyl-substituted TPZs (2 and 4) were the strongest agents, which exhibited approximately 4–30 fold greater activities compared to those of TPZ (1) along with the reference drugs chloramphenicol (CAM) and nitrofurantoin (NFT). The inhibitory activities of the compounds were highly impacted by their structural features. No reliable relationships were established between activities and the electron-accepting potencies of the whole set of studied compounds, while the activities of TPZ drug (1) and the structurally uniform set of molecules (2–6) were found to increase with an increase in their electron-accepting potencies obtained by means of density functional theory (DFT) computation. A greater steric, lipophilic and polar nature of the substituents led to a lower activity of the compounds. The combined antibacterial in vitro trial gave clear evidence that TPZs coupled with the commonly utilized antibiotics ciprofloxacin (Cipro) and nitrofurantoin (NFT) could generate enhanced (suggestive of partial and virtually complete synergistic) and additive effects. The strongest effects were defined for TPZs–NFT combinations, which resulted in a notable reduction in the MICs of di-N-oxides. These preliminary findings suggest that the synthesized novel di-N-oxides might be used as sole agents or applied as antibiotic complements.

Diastereoselective sp3 C-O Bond Formation via Visible Light-Induced, Copper-Catalyzed Cross-Couplings of Glycosyl Bromides with Aliphatic Alcohols.

Copper-catalyzed cross-coupling reactions have become one of the most powerful methods for generating carbon-heteroatom bonds, an important framework of many organic molecules. However, copper-catalyzed C(sp3)-O cross-coupling of alkyl halides with alkyl alcohols remains elusive because of the sluggish nature of oxidative addition to copper. To address this challenge, we have developed a catalytic copper system, which overcomes the copper oxidative addition barrier with the aid of visible light and effectively facilitates the cross-couplings of glycosyl bromides with aliphatic alcohols to afford C(sp3)-O bonds with high levels of diastereoselectivity. Importantly, this catalytic system leads to a mild and efficient method for stereoselective construction of α-1,2-cis glycosides, which are of paramount importance, but challenging. In general, stereochemical outcomes in α-1,2-cis glycosidic C-O bond-forming processes are unpredictable and dependent on the steric and electronic nature of protecting groups bound to carbohydrate coupling partners. Currently, the most reliable approaches rely on the use of a chiral auxiliary or hydrogen-bond directing group at the C2- and C4-position of carbohydrate electrophiles to control α-1,2-cis selectivity. In our approach, earth-abundant copper not only acts as a photocatalyst and a bond-forming catalyst, but also enforces the stereocontrolled formation of anomeric C-O bonds. This cross-coupling protocol enables highly diastereoselective access to a wide variety of α-1,2-cis-glycosides and biologically relevant α-glycan oligosaccharides. Our work provides a foundation for developing new methods for the stereoselective construction of natural and unnatural anomeric carbon(sp3)-heteroatom bonds.

Computational Insight into the Scope of the Staudinger Cycloaddition Reaction for the Preparation of β‐Lactams

AbstractThe Staudinger cycloaddition reaction represents an efficient way to readily afford β‐lactams from ketenes and imines in an asynchronous [2+2] process. Herein, a computational evaluation of the scope of the Staudinger cycloaddition reactions was undertaken by using simplified molecular models. The results pointed out that the kinetics and thermodynamics of the reaction are independent of the substituents of the imine and are essentially determined by the steric and electronic nature of the substituents of the α‐position of the ketene, being the latter the one that exerts a more dominant effect on the global feasibility of the reaction.

Reactions of a Bis(vinyltrimethylsilane)nickel(0) N-Heterocyclic carbene complex with organic azides

The reactions of three-coordinate iron(0) and cobalt(0) alkene complexes (NHC)M(η2-CH2CHSiMe3)2 (NHC = N-heterocyclic carbene, M = Fe, Co) with organic azides proved an effective way for the preparation of iron and cobalt terminal imido complexes. The relevant reactions of nickel(0) alkene complex (NHC)Ni(η2-CH2CHSiMe3)2 with organic azides, however, have remained unexplored. Herein, we report the study on the reactions of [(IPr)Ni(η2-CH2CHSiMe3)2] (IPr = 1,3-bis(2′,6′-diisopropylphenyl)imidazole-2-ylidene) with organic azides. The interaction of [(IPr)Ni(η2-CH2CHSiMe3)2] with 2,6-dimesitylphenyl azide (DmpN3) produced the two-coordinate imido complex [(IPr)Ni(NDmp)] (1) in a trace amount with the starting materials being largely remained. The reaction of [(IPr)Ni(η2-CH2CHSiMe3)2] with 2,6-diisopropylphenyl azide (DippN3) gave IPrNNNDipp (2) as the only isolable product. The interaction of [(IPr)Ni(η2-CH2CHSiMe3)2] with PhC(CF3)2N3 produced an azanickelacyclobutane compound [(IPr)Ni(κ-C,N–N(C(CF3)2Ph)CH(SiMe3)CH2)] (3) in high yield. The different products formed in these reactions reflect the influence of the steric and electronic nature of organic azides on reaction outcomes. Further study on the azanickelacyclobutane complex 3 indicated that it can convert into a new azanickelacyclobutane [(IPr)Ni(κ-C,N–N(C(CF3)2Ph)CH2CHSiMe3)] (4). A nickel(II) amido alkyl complex [(IPr)Ni(NHC(CF3)2Ph)(CH2CHNC(CF3)2Ph)] (5) was also isolated from the decomposition reaction of 3.

Kinetic Resolution of Racemic 2‐Hydroxyarylketones by Asymmetric Esterification: Investigation of the Influence of the Co‐Base on the Selectivity

AbstractAn efficient kinetic resolution of a variety of racemic 2‐hydroxyarylketone derivatives was developed by asymmetric esterification protocol using diphenylacetic acid, pivalic anhydride, and a catalytic amount of (R)‐benzotetramisole ((R)‐BTM). It was revealed that employing a tertiary amine as a co‐base in this reaction is not necessary to achieve high s‐values. All conducted reactions proceeded smoothly with good s‐values under the optimized reaction conditions, irrespective of the steric and electronic nature of the substituents on the aromatic rings of the substrates. The most stable transition state of the reaction was determined by density functional theory (DFT) calculations.