bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Mechanics Modeling of the Interactions between the Active Domain of CAP18106–137 and Lipid A
Authors: Lee Kuei‐Jen 
Published: May 2015

AbstractIn this work, a computer search with molecular mechanics calculations is applied to determine the possible low‐energy configurations of two adjacent molecules, CAP18106–137 and lipid A. This computer search is performed by systematically searching the five degrees of freedom that define the relative orientations of the two adjacent molecules. Hydrophilic and hydrophobic units are separated into several small domains along the CAP18106–137 molecule so that it can interact with the lipid A either through the Coulombic interactions with the diphosphoryl head group or through the hydrophobic interactions with the fatty acyl chains. The intermolecular interactions are calculated through the van der Waals and Coulombic interactions. The Coulombic interactions are calculated by using a dielectric constant either with a value of unity ϵ = 1 or with a distance‐dependent dielectric function ϵ(r) = rij. Based on the 400 lowest searched configurations, the intermolecular interactions calculated with ϵ = 1 are found to be about sevenfold lower than those calculated with ϵ(r) = rij. Based on the inspection of the sixteen snapshots of molecular associations, the hydrophobic interactions calculated with ϵ(r) = rij are more favorable than those calculated with ϵ = 1. The high population of the lipid A binding to the CAP 18106–137 molecule is located within the first 19 residues near the N‐terminus of the peptide, as calculated either with e = 1 or with ϵ(r) = rij, by observing the diphosphoryl groups of the lipid A. The orientations of the lipid A with respect to the CAP18106–137 molecule complete an angle of 260°, which appose to the positively charged residues in the N‐terminal half by using the helical wheel projection of the peptide.
Synthesis and Structures of [Mo12E16(PEt3)10] (E = S, Se)
Authors: Amari Shingo , Imoto Hideo , Saito Taro 
Published: May 2015

AbstractDodecanuclcar cluster complexes [Mo12S16(PEt3)10] 1 and [Mo12Se16(PEt3)10] 2 have been prepared by the reactions of [Mo6S8(PEt3)6] with sulfur or [Mo6Se8(PEt3)6] with Cp2TiSe5, respectively, in toluene at refluxing temperature. The structures have been determined at 173 K by X‐ray crystallography. The compound 1·3CHCl3 crystallizes in the triclinic space group \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm P}\bar 1 $\end{document}, with a = 14.859(5) Å, b = 15.868(4) Å, c = 14.200(7) Å, α = 100.58(3)°, β = 117.58(3)°, γ = 79.53(2)°, V = 2899(1) Å3, and Z = 1. Full‐matrix least‐squares refinement using 9016 observed reflections (Io > 2σ(Io)) gave R = 0.056, and Rw = 0.045. The data for 2·2CHCl3 are: triclinic, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm P}\bar 1 $\end{document}, a = 15.737(4) Å, b = 18.763(9) Å, c = 13.062(4) Å, α = 102.45(3)°, β = 128.54(2)°, γ = 69.49(3)°, V = 2825 Å3, Z = 1, R = 0.096, and Rw = 0.120 for 5922 reflections (Io > 2σ(Io)). The cluster complexes 1 and 2 have two octahedral molybdenum cluster units linked by the rhomboidal intercluster Mo2(μ4‐E)2 bonding. The intercluster Mo—Mo distances in 1 are 3.419 Å and 2 3.551 Å. The cyclic voltammetry of 1 and 2 shows two oxidation and two reduction steps separated as large as 380–490 mV. The UV‐Vis spectra of the dodecanuclear cluster complexes 1 and 2 have an extra weak band at around 744 nm which is absent in the starting octahedral cluster complexes.
Isomerization of n‐Hexane over Chlorinated Pt/γ‐Al2O3 Catalysts
Authors: Chu Hon Yue , Rosynek Michael P. , Lunsford Jack H. 
Published: May 2015

AbstractChlorided 0.57 wt. % Pt/γ‐Al2O3 is a moderately active and highly selective catalyst for the isomerization of n‐hexane at 300 °C when an excess of H2 is present. Chlorine, which is continuously lost from the catalyst, may be replaced by adding a small amount of chloroform to the reactant stream. The catalyst exhibits activity and high isomerization selectivity even at 150 °C. Under the conditions of these lower temperature experiments, the equilibrium concentration of C6 alkenes would be only 8 × 10−7 Torr. This suggests that the classical mechanism, which involves the formation of n‐hexene on the Pt, is not applicable. Rather, it is proposed that isomerization of the alkane occurs at acid sites on the catalyst, and the role of Pt is to catalyze the hydrogenation of any alkenes that might be formed as a result of cracking reactions. At temperatures ≤ 300 °C Brönsted acid sites are present in the catalyst, and presumably are responsible for the isomerization and cracking activity, but at higher temperatures Lewis acid sites play a dominant role.
Room‐Temperature Near‐Infrared Metastable Species Measured by Phase‐Sensitive Lock‐in and Fourier Transform Techniques
Authors: Chou Pi‐Tai , Chen Youn‐Chan , Chen Shu‐Juan , Lee Min‐Zen , Wei Ching‐Yen , Wen Tsai‐Chuan 
Published: May 2015

AbstractAn ultrasensitive detecting system coupled with either a lock‐in or Fourier transform technique has been used to detect near‐infrared (1000‐2500 nm) metastable species in room temperature solutions. These species include O2(1Δg), O2(1σ+g), the solvent induced satellite peak of molecular singlet oxygen (1Δg) emission, and the triplet state of bis(triisobutylsiloxy)silicon‐2,‐3‐naphthalocyanine (SilNC). Using the O2(1Δg) emission in benzene as a standard, the quantum yield and radiative decay rate of SiINC triplet state have been determined. Depending on types of spectral acquisition, special techniques such as phase‐distinguishing and step scan capabilities were utilized. Their advantages and disadvantages are discussed.
Kinetic Study of the Substitution Reactions of Triphenylphosphine with Chlorobenzyl Chlorides, Dimethylbenzyl Chloride, and Methylbenzyl Bromides in Various Two‐Phase Organic Solvent/Water Media
Authors: Shieh Ruey‐Lone , Lin Ruey‐Lih , Hwang Jiann‐Jyh , Jwo Jing‐Jer 
Published: May 2015

AbstractThe kinetics of the substitution reactions of triphenylphosphine (TP) with chlorobenzyl chlorides (CBC), 2,5‐dimethylbenzyl chloride (DMBC), and methylbenzyl bromides (MBB) in aprotic organic solvent was studied under the extraction by water. The effects of water, agitation, organic solvent, reactant, and temperature were investigated. These reactions take place via the SN2 mechanism and exhibit large and negative entropy of activation. The order of relative activity of solvents is CHCl3 > CH2Cl2 ≫ C6H6. In CHCl3, the order of relative reactivity of benzyl chloride (BC), benzyl bromide (BB), CBC, DMBC, and MBB toward reaction with TP is 2‐MBB > 4‐MBB > 3‐MBB > BB > DMBC > BC > 2‐CBC > 4‐CBC > 3‐CBC. These reactions produce quantitatively benzyltriphenylphosphonium salts, which are useful for synthesizing Z‐form isomers of stilbenes via the two‐phase Wittig reaction.
Studies on Condensed Heterocyclic Compounds XVII. Synthesis of 6‐(1‐Aryl‐5‐methyl‐1,2,3‐triazol‐4‐yl)‐3‐phenyl‐s‐triazolo[3,4‐b]‐1,3,4‐thiadiazoles
Authors: Sun Xiao‐Wen , Zhang Yan , Zhang Zi‐Yi 
Published: May 2015

AbstractTreatment of 4‐amino‐5‐mercapto‐3‐phenyl‐1,2,4‐triazole 2 with 1‐aryl‐4‐carboxy‐5‐methyl‐1,2,3‐triazoles 1a‐1j in a one‐step reaction yielded several 6‐(1‐aryl‐5‐methyl‐1,2,3‐triazol‐4‐yl)‐3‐phenyl‐s‐triazolo[3,4‐b]‐1,3,4‐thiadiazoles 3a‐3j. The structures of all the products were established on the basis of elemental analyses and spectral data. The fragmentation of the mass spectra of 3a‐3j under electron impact was discussed.
Isolation and Characterization of intermediate in the Synthesis of α‐Fluorodiesters
Authors: Tsai Hou‐Jen 
Published: May 2015

AbstractThe anion [(EtO)2P(O)CFCO2Et]−Li+, pregenerated from its precursor diethyl (carboethoxyfluoromethyl)phosphonate (EtO)2P(O)CFHCO2Et and n‐butyllithium, was added via syringe to a THF solution of ethyl oxaiyl chloride to yield an acylated phosphonate (EtO)2P(O)CF(COCO2Et)CO2Et. In situ reaction with Grignard reagents RMgX produces the α‐fluorodiesters (E,Z)‐R(CO2Et)C=CFCO2Et in good yields. In contrast, addition of ethyl oxalyl chloride to a THF solution of diethyl (carboethoxyfluoromethyl)phosphonate anion gives an isolated intermediate (EtO)2P(O)CFCO2Et(CO2Et)C=CFCO2Et. Subsequent reaction of this isolated intermediate with Grignard reagents also affords a one‐pot synthesis of the α‐fluorodiesters with high E‐stereoselectivity. The E‐stereoselectivity increases when HMPT or DMPU is used as a cosolvent in the preparation of diethyl 2‐fluoro‐3‐phenylfumarate (E,Z)‐Ph(CO2Et)C=CFCO2Et.
Metal‐Support interaction in Silica‐Supported Cobalt Catalyst
Authors: Ho Sui‐Wen 
Published: May 2015

AbstractThe variations in catalytic properties for CO hydrogenation and adsorptive properties for H2 and CO of silica‐supported cobalt catalyst as a function of reduction temperature (400 to 700 °C) were investigated. A mild sintering of cobalt metal from 130 Å to 145 Å occurred only when the reduction temperature was further increased from 600 to 700 °C. However, a monotone decrease in the activity (per gram Co) for CO hydrogenation was observed with increasing reduction temperature. This is accompanied with a decrease in methane and an increase in olefin formation. The decrease in activity can not be accounted for by the variation of crystallite size of cobalt metal. A concurrent suppression in the amount of hydrogen and CO adsorptions was observed after reduction temperature was raised to 700 °C. The turnover frequencies, based on cobalt dispersion estimated from H2 and CO chemisorption, remained, more or less, similar with increasing reduction temperature from 400 to 600 °C, but increased ca. 3 and 1.5 times, respectively, at 700 °C. The relative amount of subcarbonyl species (2062 cm−1) with respect to the linear adsorbed CO (2010 cm−1) was found to increase as well. Furthermore, reduction of silica surface at 700 °C was indicated by the presence of ˜Si‐H, which was detected by infrared spectroscopy at 2294 cm−1. This shows the presence of metal‐support interaction for silica‐supported cobalt systems after reduction treatment at 700 °C.
A Novel Convenient Method to Synthesize Unsymmetrical 1,1′‐Disubstituted Ferrocenes Consisting of Various Phosphino, Thiolato and Pyridyl Substituents
Authors: Dong Teng‐Yuan , Chang Chung‐Kay 
Published: May 2015

AbstractA novel convenient method for preparing unsymmetrical 1,1′‐disubstituted ferrocenyl phosphine ligands by using the readily accessible 1,1′‐dibromoferrocene as a precursor is described. The method is of interest for modifying the chelating ferrocenyl phosphine ligands in view of the growing influence of homogeneous catalysis in organic synthesis, manipulation of materials and production of high optical yield.
The Evolution of Chiral Stationary Phases for Liquid Chromatography
Authors: Armstrong Daniel W. 
Published: May 2015

AbstractThe development of effective chiral stationary phases (CSPs) and separation strategies for the liquid chromatographic (LC) resolution of enantiomers has been beneficial to many scientific disciplines. Over the last decade the number and type of CSPs has expanded tremendously. Not only have new classes of chiral selectors been introduced, but also many of the first CSPs have been changed and/or improved. The second or third generation of a CSP often can be different from the original. This can be confusing and intimidating to someone just entering the area of LC enantiomeric separations. Fortunately, all CSPs can be categorized in one or another of a few classes. There are generally one or two columns that can accomplish the majority of separations in each class. In this work we look at the different classes of CSPs and how they have expanded and changed over the last decade.
Recent Advances in Solid Acid‐Base Catalysis and Future Problems
Authors: Tanabe Kozo 
Published: May 2015

AbstractRecent advances in acid‐base catalysis are summarized. Several examples of solid acid, base, and acid‐base bifunctional catalysis which have brought significant progress of the field or are considered to give strong impacts to industrial application are presented. Selected commercialized processes developed by using solid acid‐base catalysts are demonstrated, their significance being discussed. The future problems in this field are speculated and important fundamental research subjects are pointed out.
Reactions of 7‐Chloro‐1,3‐dihydro‐1‐methyl‐5‐phenyl‐2H‐1,4‐benzodiazepin‐2,2‐dioxide in Various pH Solutions
Authors: Yang Shen K. 
Published: May 2015

AbstractDiazepam (1) is a frequently prescribed hypnotic/anxiolytic drug worldwide. 7‐Chloro‐1,3‐dihydro‐l‐methyl‐5‐phenyl‐2H‐1,4‐benzodiazepin‐2,2‐dioxide (2) is an initial alkaline hydrolysis product of 1. The mechanisms in the conversion of 2 to 2‐methylamino‐5‐chloro‐α‐(phenylbenzylidene)glycinate (3), 2‐methylamino‐5‐chlorobenzophenone (4), and 1 in aqueous solutions with pH ranging from 0 to 12.2 is the subject of this report. Results of temperature‐dependent hydrolysis kinetics and product identification indicated that: (1) in solutions with pH between 7 and 12.2, 2 underwent a ring‐opening reaction to form 3; the rate decreased with increasing pH. (2) In solutions with pH between 2 and 7, 2 was rapidly converted to 3, followed by a pH‐dependent conversion to 4; the rate increased with decreasing pH and became less sentitive to pH at pH ≤ 4.5. (3) In solutions with pH between 0 and 2, 2 was rapidly converted to 4 and 1; the percentage of 1 increased with decreasing pH. (4) A 2 containing one oxygen‐18 atom lost 50% of its oxygen‐18 following conversion to 1 in 1 M HCl. In addition to understanding the mechanism in the transformations of 2 in various pH solutions, this study established a simple and efficient method in the quantitative conversion of 1 to 4 and in the preparation of an oxygen‐18‐containing 1 at C2 position.
Alkoxide‐Accelerated [1,3] Sigmatropic Shift of Bicyclo[3.2.1]oct‐6‐en‐2‐ols to 8‐endo‐Hydroxybicyclo[3.3.0]oct‐2‐en‐4‐ones
Authors: Chen Yeh‐Long , Chang Chi‐Kang , Chang Nein‐Chen 
Published: May 2015

AbstractBicyclo[3.2.1]oct‐6‐en‐2‐ols 6 are shown to undergo [1,3] sigmatropic shift to afford 8‐endo‐hydroxy‐bicyclo[3.3.0]oct‐2‐en‐4‐ones 8 under the influence of potassium hydride.
The Effects of M2O3 on Stabilizing Monocopper over the Surface of Cu‐ZnO‐M2O3 Catalysts for Mathanol Synthesis
Authors: Chen Hong‐Bo , Liao Dai‐Wei , Yu La‐Jia , Yi Jun , Zhang Hong‐Bin , Tsai Khi‐Rui 
Published: May 2015

AbstractThe effects of M3O3 (M = Al, Sc etc.) in Cu‐ZnO‐M2O3 catalysts on methanol synthesis at low pressure were studied with ESR, XPS and TPR spectroscopy. The results of ESR showed that the generation of monovalent cationic defects was because the valence state and electronic charge on the ZnO lattice lost their balance as M3+ doped into ZnO. The induced effect by Sc3+ is stronger than that by Al3+. The results of XPS and TPR indicated that the amount and stabilization of Cu+ on the surface of reduced copper‐based catalyst and its catalytic activity were affected by the monovalent cationic defects on the surface of ZnO.
Synthesis, Crystal Structure, Cryomagnetic Properties and Catalytic Activity for H2O2 Disproportionation of New Dinuclear and Polynuclear Bis(2,4‐pentanedionate)manganese(II) Complexes with Diazine Ligands
Authors: Hong D. M. , Wei H. H. , Chang K. H. , Lee G. H. , Wang Yu 
Published: May 2015

AbstractThe structures, magnetic properties, and catalytic activity for H2O2 disproportionation are reported for three new complexes [Mn2(acac),(pydz)] (1), [Mn(acac)2(pym)] (2), and (Mn(acac)2(pyz)] (3) (acac = 2,4‐pentanedionate, pydz = pyridazine, pym = pyrimidine, pyz = pyrazine). The X‐ray crystal structures of 1 and 3 have been determined. Complex 1 crystallizes as a binuclear complex with η2‐pyridazine and acac bridging ligands 3 crystallizes as a linear polymeric chain with bridging pyrazine molecule. Cryomagnetic investigations (4‐300 K) reveal a weak intramolecular antiferromagnetic spin exchange with J = −2.05, −0.04, and −0.05 cm−1 for the complexes of 1, 2, and 3, respectively. The complexes 1–3 showed two‐step catalytic activity for H2O2 disproportionation in pyridine solution at 0 °C.
Thermal Stability of Robust Unsymmetrical Copperporphyrins with Multiple Diphenylamino and Nitro Substituents
Authors: Chen Chin‐Ti , Cha I , Hsieh Shih Jung 
Published: May 2015

AbstractThe syntheses and thermal stability properties of a series of amino and nitro substituted copperporphyrins are described. The thermal decomposition temperatures of the porphyrins were determined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). The on‐set thermal decomposition temperatures of the unsymmetrical porphyrins were found to be high in the range of 350 – 405 °C (DSC), 374 – 441 (TGA in air), 395 – 411 °C (TGA under nitrogen atmosphere), and 410 – 424 °C (DTA in air). Substituent dependent thermal stability trends were also studied. The trend is variable depending on the thermal analysis technique utilized. Possible reasons for such variation are discussed. These porphyrins are thermally robust even in the melamine‐based sol‐gel matrix. Containing 20% by weight of the substituted unsymmetrical copperporphyrin, melamine‐based sol‐gel showed no indication of decomposition until −400 °C.
Thermal and Photofragmentation of N‐Benzoylhydrazone Derivatives
Authors: Gaber Abd El‐Aal M. , Mohamed Shaaban K. 
Published: May 2015

AbstractTwo selected benzoylhydrazones I and II were subjected to thermolysis by reflux at 200 °C. Benzil, benzoic acid, biphenyl, benzanilide together with the corresponding ketones, nitriles and imines were isolated. Similar treatment of the third hydrazone III at 250 °C afforded, in addition to the previous products, bibenzyl, stilbene, and 2‐phenylindole. Photolysis of the same hydrazones I‐III in acetonitrile gave the previously reported products but in different ratios along with azine derivatives and substituted methanes. A free radical mechanism involving homolysis of the N‐N and C‐N bonds is suggested, substantiated by trapping of phenyl radical with isoquinoline, to account for the formation of the identified products.
The Synthesis of 5, 6, 7, 7a‐Tetrahydro‐1‐methyl‐3H‐pyrrolizin‐3‐one by the Palladium‐Catalyzed Cyclization of N‐Bromoacetyl‐2‐vinylpyrrolidine
Authors: Yang Sbyh‐Chyun , Shea Fang‐Rong , Hung Chung‐Wei 
Published: May 2015

AbstractN‐Bromoacetyl‐2‐vinylpyrrolidine underwent cyclization to give a pyrrolizidine derivative in the presence of a base and a catalytic amount of palladium catalyst.
Synthesis and Biological Activities of Aryl Propargyl Sulfone
Authors: Wu Ming‐Jung , Lin Chi‐Fong , Chang Li‐Juan , Jing Pao‐Tzu , Duh Tsai‐Hui , Tseng Wuan‐Ting , Lee Fang‐Chen , Wang Shan‐Shue , Chang Hsueh‐O 
Published: May 2015

AbstractA series of molecules containing monopropargyl sulfone or 1, 2‐bis‐propargyl sulfone were synthesized. The cytotoxicity of these compounds against human carcinoma cells was also examined. This study indicated that the formation of a biradical intermediate is important to the potency of cytotoxicity.
Rate Study for Electron Transfer of Sml2 to the Carbonyl Compounds and the Sulfoxides
Authors: Lin Tzuen‐Yeuan , Fun Ming‐Ren S. , Chang Shih‐Chun , Lin Yu‐Sheng 
Published: May 2015

AbstractThe rate constants for the electron transfer of samarium diiodide to 2‐heptanal, 2‐methyl valeraldehyde and diphenyl sulfoxide were obtained for the first time. The reaction is first order in these substrates and there are hints that the reaction rate has a strong steric dependence. HMPA exhibited a profound catalytic effect but t‐BuOH did not. The effect of temperature on reaction rates was also obtained.
Acceleration Effect of Fe(II), Co(II), Ni(II) and Cu(II) on the Hydrolysis Rate of Ortho‐ or Para‐Hydroxy Schiff Bases
Authors: El‐Taher M. A. 
Published: May 2015

AbstractThe kinetics of hydrolysis of ortho‐ or para‐hydroxybenzylidene‐4‐benzidine Schiff bases have been examined in the pH range 1.70–11.90, in aqueous media containing 20wt% dioxane, at 20 °C. In basic media, pH > 8.47, a slight increase in the hydrolysis reaction rate of the Schiff bases is observed. In such basic media, the rate‐controlling step is the attack of hydroxide ion on the ionized Schiff base. Below pH 6.82, the rate‐determining step is ascribed to be the attack of water molecules on the protonated substrate. The effects of Fe(II), Co(II), Ni(II) and Cu(II) ions on the hydrolysis reaction rate of the Schiff bases have been studied and discussed on the basis of formation of a monocyclic chelate rings. The various thermodynamic parameters have also been evaluated and discussed.
Preliminary Study on Reverse Pulse Amperometric Detection in Capillary Electrophoresis for Simultaneous Determination of Cysteine and Cystine
Authors: Hsi Tai‐Sung , Chuang May‐Yin 
Published: May 2015

AbstractSimultaneous determination of cysteine (RSH) and cystine (RSSR), two important sulfur‐containing amino acids, in capillary electrophoresis (CE) has been an analytical task. Dual‐microelectrode amperometric detection seems to be a good scheme, but significant difficulty in electrode construction and poor detection limit for RSSR determination remain major short‐comings. In reverse pulse amperometric (RPA) detection, the applied potentials are repeatedly pulsed back and forth between the reducing initial potential (e.g., Ei = −1.4 V) and the oxidizing final potential (e.g., Ef = 0.0 V) at a single, gold‐mercury amalgam (Au/Hg) microelectrode. At Ei, RSSR is reduced to RSH which causes catalytical oxidation of the Au/Hg amalgam microelectrode when the potential is pulsed to Ef. The resulting anodic current is then recorded. Therefore, by using RPA detection after CE separation, RSH and RSSR can be simultaneously determined.
Electrochemical Methoxylation of 1,2,3‐Trisubstituted Azulenes
Authors: Chen Arh‐Hwang 
Published: May 2015

Abstract1,2,3‐Trisubstituted azulene analogs 6a and 6b easily underwent methoxylation in position 4 or 6 of an azulene ring via an electrochemical oxidation. It is a simple, convenient and selective method for introducing a methoxy group into a 7‐membered ring of azulene analogs when compared with traditional chemical methods. It could be useful in preparing 2,4‐ and 2,6‐azuloquinone analogs.
The Syntheses of Triazinone and Pyrimidinone Biphenyltetrazoles as Angiotensin II Receptor Antagonists
Authors: Choir Shan‐Yen , Yang Paw‐Hwa , Wang Chia‐Lin J. , Lu Hsiao‐Hwa , Chen Yin , Kao Jen‐Mann 
Published: May 2015

AbstractA series of biphenylyltetrazole substituted triazinones and structure‐related pyrimidinones are systhesized, and their binding affinities for angiotensin II receptor are reported.
Reactions of 4‐Hydrazinocarbonylmethylene 3‐Arylsydnones and 3‐(4‐Hydrazinocarbonylphenyl)sydnones
Authors: Lin Shaw‐Tao , Yang Mein‐Lin , Tien Hsien‐Ju 
Published: May 2015

AbstractThe phenyl ring of 3‐(4‐hydrazinocarbonylphenyl)sydnone activates a hydrazinocarbonyl group to undergo a series of reactions for preparing heterocyclic compounds including oxadiazoles, dihydropyrroles, and pyrroles. However, the hydrazinocarbonyl group on the C(4)‐CH2 resists a cyclization under the same reaction conditions.