bluuebunny/crossref_metadata_2025_split huggingface dataset:
The reaction of diphenyltin (IV) or triphenyltin (IV) chloride with 3,4,5‐trimethoxybenzoyl salicylahydrazone. The crystal structure of Ph2[(MeO)3C6H2C(O)N2CHC6H4O]Sn
Authors: Yu Zhengkun , Yan Shenggang , Zheng Peiju , Chen Jian 
Published: January 2005

AbstractThe title complex has been synthesized by the reaction of diphenyltin(IV) or triphenyltin(IV) chloride with 3,4,5‐trimethoxybenzoyl salicylahydrazone and characterized by 1H, 13C, 119Sn NMR, and IR spectral studies. An X‐ray analysis shows that the ligand is tridentate and approximately planar and the central tin atom is in a distorted five‐coordinate trigonal bipyramidal geometry. The complex crystallizes in the monoclinic space group C2/c with a = 29.194(4), b = 10.117(1), c = 22.524(3) Å, β = 124.44(2)°, V = 5486.5(8) Å3, Z = 8. The SnC bond lengths are 2.123(9) and 2.116(7) Å, and the bond length between the tin atom and the coordinating nitrogen atom (Sn–N bond) is 2.152(6) Å. The CSnC bond angle and the bond angle between the tin atom and the two axially positioned oxygen atoms are 129.1(1) and 156.17(9)°, respectively. The structure was refined to final R = 0.056 and Rw = 0.074 for 4145 observed reflections with I > 3σ(I). © John Wiley & Sons, Inc.
The pummerer and the thio‐claisen–type rearrangements of naphtho[1,8‐bc]‐1,5‐dithiocin monooxide and N‐p‐tosylsulfilimine
Authors: Furukawa Naomichi , Shima Hidetaka , Ogawa Satoshi 
Published: January 2005

AbstractNaphtho[1,8‐bc]‐1,5‐dithiocin N‐p‐tosylsulfilimine (8) and monosulfoxide (9) were prepared. On treatment with conc. H2SO4, both the sulfilimine (8) and sulfoxide (9) gave the dithia dication which was converted to the sulfoxide by hydrolysis. The H–D exchange reaction of (8) took place highly regioselectively to afford the monodeuterated (8–D) at the a‐position of the N‐tosyl group. The Pummerer rearrangement reaction of monooxide (9) with acetic anhydride gave the a‐acetoxy derivative by the dication (10b), while a new thio‐Claisen rearrangement of sulfilimine (8) t‐BuOK in CH2Cl2 gave 2‐allyl‐naphtho[1,8‐bc]‐1,5‐dithiole. © John Wiley & Sons, Inc.
Nitriles in heterocyclic synthesis: The reaction of ethyl 2‐oxoindoliden‐3‐ylidene cyanoacetate and of 3‐dicyanoethylideneindoliden‐2‐one with phenols and amines
Authors: Sadek Kamal Usef , Selim Maghraby Ali , Ali Mohamed , Elnagdi Mohamed Hilmy 
Published: January 2005

AbstractThe reactions of ethyl 2‐oxoindoliden‐3‐ylidene cyanoacetate (2a) and of 3‐dicyanoethylideneindoliden‐2‐one (2b) with phenols and amines have been reported. © John Wiley & Sons, Inc.
The reaction between dicyclopentadienyl‐dicarbonyl titanium and aryltin halides
Authors: Wang Ji‐Tao , Xu Yu‐Ming , Zhang Zhi‐De 
Published: January 2005

AbstractThe oxidation‐elimination reaction between dicyclopentadienyl‐dicarbonyl titanium, Cp2Ti(CO)2 [bis(methylcyclopentadienyl)dicarbonyl titanium, (MeCp)2Ti(CO)2] and aryltin halides was studied. Nineteen novel complexes containing the Ti–Sn bond were isolated. The reaction was proved to involve freeradical intermediates. © John Wiley & Sons, Inc.
Acetylcarnitine induces heme oxygenase in rat astrocytes and protects against oxidative stress: Involvement of the transcription factor Nrf2
Authors: Calabrese Vittorio , Ravagna Agrippino , Colombrita Claudia , Scapagnini Giovanni , Guagliano Eleonora , Calvani Menotti , Butterfield D. Allan , Giuffrida Stella Anna Maria 
Published: January 2005

AbstractEfficient functioning of maintenance and repair processes seem to be crucial for both survival and physical quality of life. This is accomplished by a complex network of the so‐called longevity assurance processes, under control of several genes termed vitagenes. These include members of the heat shock protein system, and there is now evidence that the heat shock response contributes to establishing a cytoprotective state in a wide variety of human conditions, including inflammation, neurodegenerative disorders, and aging. Among the various heat shock proteins, heme oxygenase‐1 has received considerable attention; it has been recently demonstrated that heme oxygenase‐1 induction, by generating the vasoactive molecule carbon monoxide and the potent antioxidant bilirubin, could represent a protective system potentially active against brain oxidative injury. Acetyl‐L‐carnitine is proposed as a therapeutic agent for several neurodegenerative disorders. Accordingly, we report here that treatment of astrocytes with acetyl‐L‐carnitine induces heme oxygenase‐1 in a dose‐ and time‐dependent manner and that this effect was associated with up‐regulation of heat shock protein 60 as well as high expression of the redox‐sensitive transcription factor Nrf2 in the nuclear fraction of treated cells. In addition, we show that addition of acetyl‐L‐carnitine to astrocytes, prior to proinflammatory lipopolysaccharide‐ and interferon‐γ‐induced nitrosative stress, prevents changes in mitochondrial respiratory chain complex activity, protein nitrosation and antioxidant status induced by inflammatory cytokine insult. Given the broad cytoprotective properties of the heat shock response, molecules inducing this defense mechanism appear to be possible candidates for novel cytoprotective strategies. Particularly, manipulation of endogenous cellular defense mechanisms via acetyl‐L‐carnitine may represent an innovative approach to therapeutic intervention in diseases causing tissue damage, such as neurodegeneration. We hypothesize that maintenance or recovery of the activity of vitagenes may delay the aging process and decrease the risk of age‐related diseases. © 2005 Wiley‐Liss, Inc.
Ring‐opening metathesis polymerization (ROMP) of norbornene in supercritical carbon dioxide using well‐defined metal carbene catalysts
Authors: Hu Xiaochuan , Blanda Michael T. , Venumbaka Sreenu R. , Cassidy Patrick E. 
Published: January 2005

AbstractRing‐opening metathesis polymerization (ROMP) of bicyclo[2,2,1]hept‐2‐ene (norbornene) has been effected in supercritical carbon dioxide (SC CO2) with two types of metal carbene catalysts. It has been found that the polynorbornenes prepared in SC CO2 are similar in molecular weight, molecular weight distribution and thermal stability to their counterparts prepared in tetrahydrofuran (THF). More important, the trans/cis ratio of the resulting polymers could be adjusted by varying the amount of cosolvent THF or metal carbene catalysts. However, neither the reaction temperature nor pressure significantly influenced the trans/cis ratio of the polymer. Copyright © 2005 John Wiley & Sons, Ltd.
Avidin self‐associates with boric acid gel suspensions: preparation of an affinity boron carrier that might be developed for boron‐neutron capture therapy
Authors: Cochrane Laura , Bench Bennie J. , Johnson Rebecca , Hamilton Craig , Gooch Joey , Wright John R. 
Published: January 2005

AbstractIt has been shown in preliminary studies that avidin self‐associates with suspended arylboronic acid gel polymer particles, and avidin‐coated gel particles in the micron and submicron size range are of interest to boron‐neutron capture therapy (BNCT) applications because they carry sufficiently large amounts of boron‐10 to effect a meaningful tissue dosing through BNCT. Avidin‐coated gel particles precipitate within 46 min of mixing when the avidin/colloid ratio is about 0.34 g avidin/g colloid. This is a minimum time if gel and avidin concentrations are in the low microgram/milliliter range, and further increases in the relative amount of avidin increase the time to precipitation. At shorter exposure times rapid agglutination‐like reactions were observed with multivalent biotinylated bovine albumin, suggesting that two stage pre‐targeting of specific tissues should be possible with biotinylated antitumor antibodies. The yield of micron sized and smaller gel particles is enhanced by a combination of manual grinding in an agate mortar followed by sonification. Sonification alone produces an uneven distribution, with fewer particles sedimenting at 15 000 rpm than above or below. Preparation of avidin‐coated boronic acid particles is a matter of combining a phosphate buffered solution of avidin (120 mM in NaCl, 2.7 mM in KCl and 10 mM in phosphate, pH 7.4) and an aqueous suspension of gel particles in the mass ratio described above. Copyright © 2005 John Wiley & Sons, Ltd.
Synthesis of a low thrombogenic heart valve coating with horseradish peroxidase
Authors: Benson Adrienne M. , Omrane Kamel , Graves Erin M. , Haas Amy L. , Bryant Erica , Mandalaywala Monisha , Mueller Anja 
Published: January 2005

AbstractCardiovascular implants like artificial heart valves are made out of a variety of materials to allow for adequate mechanical properties and mechanical movement. All of these materials have different adhesion properties towards blood proteins but all still induce blood coagulation. This article describes the design and enzymatic synthesis of a heart valve coating that would adhere to different materials as well as prevent adhesion of proteins to the surface to prevent blood coagulation. It consists of two covalently linked hyperbranched polymer thin films: one that provides strong adhesion to the surface in question and another that prevents adhesion of blood proteins. The synthesis of hyperbranched polyresorcinol and linear polyhydroquinone is presented for the thin film that adheres to the artificial heart valve. The synthesis of polyglycerol and poly(glucuronic acid) is presented for the anti‐thrombogenic thin film. The polymers are synthesized by horseradish peroxidase in water or buffer. Some of these syntheses do not use any other oxidant than oxygen, and the mechanism of these reactions is currently under investigation. The syntheses still need to be characterized in more detail and optimized. These polymers will be covalently linked to form the heart valve coating. Copyright © 2005 John Wiley & Sons, Ltd.
Nucleophilic substitution at saturated carbon atoms. Mechanisms and mechanistic borderlines: Evidence from studies with neutral leaving groups
Authors: Katritzky Alan R. , Brycki Bogumil E. 
Published: January 2005

AbstractSubstrates with neutral leaving groups undergo unimolecular solvolysis in nonpolar solvents. Whereas t‐alkyl substrates invariably solvolyze by a unimolecular mechanism, s‐alkyl and primary alkyl substrates can undergo both uni and bimolecular reactions, and the bimolecular step can take place on either the substrate itself or on an intimate ion‐molecule pair formed in either a pre‐equilibrium or in a rate determining step. Study of reactions at borderlines indicates that the individual reaction types remain distinct and do not merge.
Generation of α‐ oxo selenoaldehydes by treatment of α, α′ ‐diketo selenides with base
Authors: Nakayama Juzo , Sugihara Yoshiaki 
Published: January 2005

AbstractTreatment of α, α′ ‐diketo selenides, which recently became readily obtainable, with base affords α‐oxo selenoaldehydes and ketones. The seleno‐carbonyl compounds thus formed are reactive transient species, but can be trapped by Diels‐Alder reaction to give 3,6‐dihydro‐2H‐selenapyran derivatives in moderate to good yields.
Thiophilic reactions of 2,4,6‐tri‐t‐butylphenyllithium with carbon disulfide and thiophosgene
Authors: Okazaki Renji , Fujii Takuji , Inamoto Naoki 
Published: January 2005

AbstractHighly sterically demanding 2,4,6‐tri‐t‐butylphenyllithium (1) reacts with carbon disulfide to give 1,2‐dibutylthio‐1,2‐bis(2,4,6‐tri‐t‐butylphenylthio) ethene (3), l‐butylthio‐1‐(2,4,6‐tri‐t‐butylphenylthio)pent‐l‐ene (4), and 2‐butylthio‐3‐(2,4,6‐tri‐t‐butylphenylthio)‐1,3‐dithiole‐2‐thione (5) when 1 is prepared by the reaction of 1‐bromo‐2,4,6‐tri‐t‐butylbenzene with n‐butyllithium. When the reaction is carried out using 1 prepared from 2 and t‐butyllithium and then quenched with l‐iodoethane, 2‐ethylthio‐3‐(2,4,6‐tri‐butylphenylthio)‐1,3‐dithiole‐2‐thione and 1,2‐diethylthio‐1,2‐bis(2,4,6–tri‐t‐butylphenylthio) ethene are produced. The formation of all these products can be explained in terms of initial thiophilic attack of 1 on the sulfur of carbon disulfide and an intermediate with a dual property of carbanion and carbene (i.e., ArSC(Li)(S) ⇌ ArSC̈SLi) is suggested. The reaction of 1 with thiophosgene affords 1,2‐dichloro‐1,2‐bis(2,4,6‐tri‐t‐butylphenylthio) ethene, bis(2,4,6‐tri‐t‐butylphenylthio)acetylene, and 1‐chloro 2,4,6‐tri‐t‐butylbenzene, the first two of which are explained to be formed by thiophilic attack of 1 with thiophosgene.
Theoretical studies on the acylation reactions of ammonia by ketenes: Determination of reactivity by molecular orbital theory (part 54)
Authors: Lee Ikchoon , Song Chang Hyun , Uhm Tea Seop 
Published: January 2005

AbstractTheoretical studies on the reactions of ammonia with ketene and dimethylketene using the MNDO method are reported. The single step addition of ammonia to the olefinic bond of ketenes was found to provide a lower energy‐barrier path than the two step carbonyl addition mechanism. The barrier height was lower in the reaction of keten compared with that of dimethylketene in support of the faster rate of solution phase reactions of aniline and ketenes. The deformation energies of reactants had an overwhelming influence in determining the activation barriers in all the reactions investigated.
A novel oxygen induced reduction of α, β‐unsaturated carbonyl compounds by benzeneselenol
Authors: Masawaki Teruyuki , Uchida Yuzo , Ogawa Akiya , Kambe Nobuaki , Miyoshi Noritaka , Sonoda Noboru 
Published: January 2005

AbstractA novel oxygen induced reduction of α,β‐unsaturated carbonyl compounds is discovered. The reduction of the carbon‐carbon double bond of α,β‐unsaturated carbonyl compounds by benzeneselenol was caused by an introduction of molecular oxygen into the reaction system. This reduction is likely to proceed via a radical chain pathway involving an SH2 type reaction between a phenylseleno radical and a 1,2‐adduct of benzeneselenol to the carbonyl group of the α,β‐unsaturated carbonyl compound to give an allylic radical which absracts a hydrogen atom from benzeneselenol to form the reduction product.
Synthesis of optically active 2,2′‐diselenocyanato‐1,1′‐binaphthyl and its molecular structure. Hypervalent nature of divalent selenium atom in crystal state
Authors: Tomoda Shuji , Iwaoka Michio , Yakushi Kyuya , Kawamoto Atsushi , Tanaka Jiro 
Published: January 2005

Abstract2,2′‐Diselenocyanato‐1,1′‐binaphthyl(1), the first selenium‐containing binaphthyl derivative, has been synthesized in optically active form the corresponding diamine by diazotization followed by the reaction with potassium selenocyanate. Its molecular structure is determined by X‐ray diffraction method. It is revealed that selenium atoms have hypervalent penta‐coordination in the crystal.
NMR studies on the restricted rotation of 1‐[2‐(1‐phenyl) propyl]‐2,5‐dimethylpyrrole derivatives
Authors: Kashima Choji , Maruyama Tatsuya , Fujioka Yoko , Harada Kazuo 
Published: January 2005

AbstractFrom the 1H‐NMR spectra of the various pyrrole compounds, 1‐substituted 2,5‐dimethylpyrroles having two substituent groups on the carbon adjacent to the nitrogen atom were found to be very much hindered compounds. 1‐[(1‐Substituted)‐2‐phenylethyl]‐2,5‐dimethylpyrroles showed the restricted rotation, and the phenyl group of the most stable conformer was in close proximity to the pyrrole group due to dipole interaction. These NMR observations were supported by force field conformational analysis.
Electron spin resonance study on radicals stabilized by the σ‐π captodative effect1
Authors: Sakurai Hideki , Kyushin Soichiro , Nakadaira Yasuhiro , Kira Mitsuo 
Published: January 2005

AbstractESR spectra of l‐cyano‐2‐(trimethylsilyl)ethyl and related radicals were recorded. Temperature dependent ESR spectra of these radicals revealed that electron‐releasing trimethylsilylmethyl and electron‐withdrawing cyano groups synergetically functioned to stabilize the radical centers due to σ‐π captodative effects.
Acidities of radical cations derived from arylacetonitriles
Authors: Bordwell F. G. , Cheng Jin‐Pei , Bausch Mark J. , Bares Joseph E. 
Published: January 2005

AbstractThe equilibrium acidities of phenylacetonitrile, and 20 of its m− and p‐substituted derivatives have been measured in Me2SO solution. Their pKa′s plot linearly with those of the corresponding anilines. Combination of the pKa′s of these acids with their oxidation potentials, Eox(HA), and those of their conjugate bases, Eox(A−), provide an estimate of the acidities of the corresponding radical cations. The pKHA+ values for ArCH2CN+., where Ar is Ph, 1‐ and 2‐naphthyl, and 9‐anthryl, are −32, −18·5, −17·5, and −11, respectively, compared to 21·9, 20·85, 20·65, and 19·8 for the corresponding ArCH2CN acids. Acidities of PhCH(Me)CN+., Ph2CHCN+., 9‐CN‐FlH+., and 9‐CN‐XnH+. are −33, −35, −25, and −27, respectively, compared to 23·0, 17·5, 8·3, and 13·6 for the corresponding acids from which they were derived. The homolytic bond dissociation energies (BDEs) for the benzylic CH bonds in these arylacetonitriles, estimated by combining pKHA with Eox(A−), fall in the range of 69 kcal/mol for 9‐CN‐XnH to 82 kcal/mol for PhCH2CN. For GC6H4CH2CN+. radical cations the acidities are decreased, relative to G=H, when G is an electron donor substituent and increased when G is an acceptor. The BDEs of the benzylic CH bonds in GC6H4CH2CN are weakened by up to 4 kcal/mol by para donors and strengthened by up to 1·2 kcal/mol by m‐ or p‐acceptors. The significance of these changes in BDEs with regard to the use of σ. scales and the ΔAOP method for estimating substituent effects on radical stabilities is discussed.
Acidities of benzyl phenyl sulfones and of the corresponding radical cations. Homolytic bond dissociation energies (BDEs) of αCH bonds in benzyl phenylsulfones
Authors: Bordwell F. G. , Bausch Mark J. , Branca John C. , Harrelson John A. 
Published: January 2005

AbstractThe excellent linearity (R2 = 0·997) of a plot of pKa values for 17 m− and p‐substituted benzyl phenyl sulfones, GC6H4CH2SO2Ph, vs. those for the corresponding arylacetonitrile, GC6H4CH2CN, demonstrates that substituent solvation and substituent solvation assisted resonance (SSAR) effects for p‐CN, p‐COPh, and p‐SPh are nearly identical in these two substrates. The PhSO2 group in PhCH2SO2Ph increases the BDE of the α‐CH bond by 2 kcal/mol, relative to toluene. The α‐CH bonds in GC6H4CH2SO2Ph sulfones are stabilized by 1–2 kcal/mol by acceptor G′s (m‐CN, p‐CN, m‐CF3, p‐CF3), but weakened by 1 and 5 kcal/mol, respectively, by donors (p‐OMe and p‐NMe2). The GC6H4CH2SO2Ph+. radical cation with G = H has a pK = −25. Its acidity is increased when G is an acceptor by as much as 9 to 10 kcal/mol (G = 3‐CN, 3‐CF3, 4‐CF3, 4‐NO2), but is decreased when G is a donor by as much as 33 kcal/mol (G = NMe2). When G = 4‐SPh the radical cation is stabilized, relative to G = H, by a larger amount (25 kcal/mol) than when G = 4‐OMe (18 kcal/mol). Structural changes along the series PhCH2SO2Ph, 2‐naphthyl‐CH2SO2Ph, 9‐anthryl CH2SO2Ph cause negligible changes in the acidities of these acids, but sizable decreases in the acidities of the corresponding radical cations. Introduction of a phenylsulfonyl group into the methyl group of 9‐methylanthracene or the 9‐position of fluorene or xanthene increase the BDEs by 3, 2, and 7 kcal/mol, respectively. These effects of PhSO2 groups are compared and contrasted with those of CN groups.
Photoinduced potentiometric response of poly(vinyl chloride)/spirobenzopyran/crown ether composite memberanes modified with urease
Authors: Hasebe Yasushi , Anzai Jun‐Ichi , Ueno Akihiko , Osa Tetsuo , Chen Chien‐Wu 
Published: January 2005

AbstractPhotoresponse of the poly(vinyl chloride) membranes, which contain spirobenzopyran and crown ether, covered with a urease layer was studied in the presence and absence of urea. In the absence of urea, UV light irradiation induced more than 160 mV of membrane potential change, whereas the photoresponse decreased with an increase in the concentration of urea in the solution. The effects of such operating variables as crown loading and pH and ionic strength in the aqueous phase on the potentiometric response were also elucidated in the presence of urea. The results were explicated using the fact that the local concentration on NH4+ and H+ ions changed as a result of the urease‐catalyzed decomposition reaction of urea.
Novel reactions of sterically protected fused 1,2,3‐selenadiazole. A new aspect of reactivity of organoselenium intermediates
Authors: Ando Wataru , Kumamoto Yorio , Tokitoh Norihiro 
Published: January 2005

AbstractLight‐ and heat‐induced decompositions and reactions with nucleophiles of 6,6,8,8‐tetramethyl‐2‐selena‐3,4‐diaza‐7‐oxabicyclo[3.3.0]octa‐ 1(5),3‐diene have been studied. In contrast with the conversion to the cyclopentyne derivative (9), selenium containing intermediates (6a, 6b, and 7) were efficiently trapped using several reagents to give various kinds of organoselenium compounds. Of particular note is the isolation of a stable selenirane derivative (16) obtained by the cycloaddition of the photochemically generated selenirene intermediate (7) with furan. The character and reactivity of the intermediates are also discussed.
The ‘dimer mechanism’ in aromatic nucleophilic substitution by amines in aprotic solvents
Authors: Nudelman Norma S. 
Published: January 2005

AbstractThe mechanism of aromatic nucleophilic substitutions by amines in protic solvents is well established; on the contrary the mechanism/s of the reactions in aprotic solvents is/are still subject of controversy. The present paper describes several systems for which fourth‐order kinetics (third‐order in amine) were observed. A mechanism is proposed to account for this as well as other observation such as: overall negative energies of activation, quadratic dependence of kA with non‐nucleophilic tertiary bases, spectacular effects of hydrogen‐bond donor (HBD) and hydrogen‐bond acceptor (HBA) catalysts, etc. Other alternative mechanisms are also discussed.
Formation of 1:1 adducts between bis(1,2‐diaryl‐1,2‐ethylenedithiolato)metal(0) (metal = NI, PD, and PT) and quadricyclane and their photodissociation
Authors: Kajitani Masatsugu , Kohara Midori , Kitayama Tomoko , Akiyama Takeo , Sugimori Akira 
Published: January 2005

AbstractBis(1,2‐diaryl‐1,2‐ethylenedithiolato)metal(0) complexes (1; metal = Ni, Pd, and Pt) react with quadricyclane (Q) to give selectively 1:1 adducts which are identical with the adducts between 1 and norbornadiene (NBD). In the adducts, two sulfur atoms of the different dithiolato ligands are added to one of the double bonds of NBD. The reactions of 1 with Q are 103–104 times faster than those with NBD. The more electropositive dithiolatometal complexes react faster with Q and NBD. The adducts are dissociated to the free dithiolatometal complexes and NBD by UV‐irradiation (254–436 nm). Upon irradiation with 254 nm light, the photodissociation occurs before the decomposition of the dithiolatometal complexes.
Switching of reaction pathways due to methylene chain length effects
Authors: Nakagaki Ryoichi , Sakuragi Hirochika , Mutai Kiyoshi 
Published: January 2005

AbstractReaction products of bifunctional chain molecules with structure X(CH2)nY may critically depend on the chain length n. When the chain length is short (n ≤ 5), reaction products particular to an intramolecular reaction can be dominant, while a process corresponding to an intermolecular reaction between XCH3 and H3CY may take place for higher homologues having large n (≥10). The reaction switching dependent on n is explained in terms of the encounter probability for both end groups (X and Y) with conformations pertinent to product formation. The reaction switching of this sort is discussed on the basis of a reactivity profile recorded as a function of the chain length. Similar reactivity profiles have been observed for thermal Friedel–Crafts cyclization and photo‐Smiles rearrangement/photoredox reaction. It is anticipated that the magic methylene chain length of 7 may give rise to an appreciable decrease in reaction yields (e.g. ‘difficulty in medium‐sized ring closure’) or an anomalous switching of reaction pathways due to chain length effects.