bluuebunny/crossref_metadata_2025 huggingface dataset:
First synthesis and structural determination of 1, 1′‐spirobis(3H‐2, 1‐benzoxatellurole)‐3, 3′‐dione ([10‐Te‐4(C202)])
Authors: Takaguchi Yutaka , Furukawa Naomichi
Published: January 2005

1, 1′‐Spirobis(3H‐2, 1‐benzoxatellurole) ‐3, 3′‐dione [10‐Te‐4(C202)] (1c) with five‐membered spirorings was prepared, and its molecular structure was determined by X‐ray crystallographic analysis. The two types of arrangement of the ligands about the central tellurium atom show considerably distorted trigonal bipyramidal (TBP) geometries. The tellurane 1c undergoes a ring‐opening reaction on treatment with aqueous sodium hydroxide to afford the telluroxide 10, which reacts with aqueous hydrochloric acid at room temperature to give again the tellurane 1c in quantitative yield. © 1995 John Wiley & Sons, Inc.
Synthesis and spectral analysis of 8‐substituted dinaphtho [2,1‐d:1′,2′‐g] [1,3,6,2]dioxathiaphosphocin 8‐oxides
Authors: Reddy B. Sankara , Anuradha K. , Reddy C. Devendranath , Kumar N. Jagadeesh , Krishnaiah M. , Berlin K. Darrell
Published: January 2005

Synthesis and spectral analysis of several 8‐substituted dinaphtho[2,1‐d:1′,2′‐g][1,3,6,2]dioxathiaphosphocin 8‐oxides have been described. An X‐ray crystallographic study of 8‐(2′,3′‐ dimethylphenoxy)dinaphtho[2,1 ‐ d:1′,2′‐g][1,3,6,2]dioxathiaphosphocin 8‐oxide has indicated that, in the solid state, the dioxathiaphosphocin ring is in a distorted‐boat–like conformation with the P = O group and bridged S atom directed away from each other. Electron impact mass spectra showed M+ and (M–OR)+ ions, containing the dioxathiaphosphocin ring system, confirming the structures of the esters. © 1995 John Wiley & Sons, Inc.
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

The 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

Naphtho[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

The 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

The 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

Efficient 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

Ring‐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

It 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

Cardiovascular 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

Substrates 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

Treatment 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

Highly 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

Theoretical 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

A 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

2,2′‐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

From 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

ESR 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

The 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

The 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

Photoresponse 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

Light‐ 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

The 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

Bis(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

Reaction 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.
Non‐hierarchical classification of organic solvents using characteristic vector analysis of physical and empirical solvent parameters
Authors: Zalewski Romuald I. , Kokocińska Henryka , Reichardt Christian
Published: January 2005

Characteristic vector analysis of a set of six physical and empirical parameters of 103 commonly used organic solvents (bp, ϵr, μ, nD, E, and δ) gives four vectors describing 95% of the total data variability. Non‐hierarchical cluster analysis, applied to our results, leads to ten separate classes of organic solvents.
Laser flash photolysis of a chromium carbene complex: Pentacarbonyl(1,3‐dimethyl‐4‐imidazolin‐2‐ylidene)chromium(0)
Authors: Oishi Shigero , Tokumaru Katsumi
Published: January 2005

Photoreactions of Cr(CO)5(Im) (Im = 1,3‐dimethyl‐4‐imidazolin‐2‐ylidene) have been investigated by laser flash and continuous photolysis. Quantum yields for the disappearance of Cr(CO)5(Im) in benzene under Ar or CO were very low, although transients observed by laser flash photolysis reacted rapidly with CO. This suggests that photodissociation of the carbene ligand is very minor. The laser flash photolysis at 337 nm in benzene (B) gave a transient (λmax = 630 nm), which converted to the second transient (λmax = 455 nm) within ∼100 ns. The kinetic studies of these transients revealed that the first one is a ‘free’ coordinatively unsaturated species (Cr(CO)4(Im)) and the second one carries a solvent molecule as a ligand (Cr(CO)4(Im)(B)). From the comparison of Cr(CO)4(Im) and Cr(CO)5, apparently lower reactivity of Cr(CO)5 was found to be due to the strong coordination of a solvent molecule. The Im ligand neutralizes the deficit of electron density on Cr. A simple synthesis of Cr(CO)5(Im) was also described.
ESCA studies of carbanionic compounds: Butyllithium in heptane solution and dibutylmercury in the gas phase
Authors: Moberg R. , Yuan Zhong Cai , Holmberg S. , Bökman F. , Ahlberg P. , Bohman O. , Siegbahn H.
Published: January 2005

Two organometallic reagents, butyllithium in heptane solution and dibutylmercury in the gas phase, have been studied by means of core electron spectroscopy. The property of particular interest was the charge polarization as reflected by the ESCA shifts. In the butyllithium compound the C1s binding energy is shifted to a lower value by 1·8 eV for C‐1 (situated closest to the Li+ ion) relative to the heptane solvent carbon. This is due to the anionic character of the C‐1. The interpretation of the experiments was supported by comparing the results with ab initio calculations made on geometry‐optimized butyllithium, butyl anion and butane.
Reflections on the π‐complex theory of benzidine rearrangements
Authors: Shine Henry J.
Published: January 2005

The ups and downs, and reasons therein, of the π‐complex theory of the mechanism of the benzidine rearrangements, and the possible role of π‐complexes in a newer understanding of the rearrangements, are described.
Analysis of solvent effect on SN2 reactions by different theoretical models
Authors: Alemán Carles , Maseras Feliu , Lledós Agustí , Duran Miquel , Bertrán Juan
Published: January 2005

The solvent effect on two SN2 reactions was evaluated by discrete, continuum and discrete–continuum models. The potential energy profiles were found to change dramatically on introduction of the solvent effect. The double‐well shape which characterizes the F− + CH3F → FCH3 + F− reaction in the gas phase becomes unimodal when the solvent is introduced, in good agreement with experimental data. The solvation parameters are found to intervene in the reaction coordinate. Recent Monte Carlo and molecular dynamics calculations are discussed.
Comparative kinetic study of solvent effects in the reactions of 1,2‐dinitrobenzene with butylamine and piperidine
Authors: Chiacchiera S. M. , Cattana R. I. , Singh J. O. , Anunziata J. D. , Silber J. J.
Published: January 2005

The kinetics of the aromatic nucleophilic substitution (SNAr) reactions of 1,2‐dinitrobenzene (1,2‐DNB) with butylamine (BA) and piperidine (PIP) were investigated as a function of the amine concentration and temperature, in chloroform, ethyl acetate, tetrahydrofuran (THF), acetonitrile (ACN), dimethylformamide (DMF), dimethyl sulphoxide (DMSO). benzene, toluene, chlorobenzene and diisopropyl ether.

In the set of solvents consisting of ethyl acetate, THF, ACN, DMF and DMSO, neither reaction is catalysed (kA=k1). The sequence and range of reactivity for BA and PIP are similar in these solvents. These results indicate that reactions in which nitro in the leaving group behave differently fromSNAr reactions with other leaving groups, such as halogens or alkoxy groups, since an intramolecular hydrogen bond may be expected between the leaving nitro group and the ammonium H of the nucleophiles. The correlations of the rate coefficients obtained with Taft and Kamlet's solvatochromic method support these conclusions.

On the other hand, these reactions show mild acceleration with relatively non‐polar solvents such as the aromatics and diisopropyl ether. The donor properties of these solvents and experiments with solvent mixtures suggest the formation of electron donor–acceptor complexes between them and 1,2‐DNB. Hence the preferential solvation of 1,2‐DNB by the donor solvent accounts for the mechanism observed.
Rate‐equilibrium LFER characterization of transition states: The interpretation of α
Authors: Lewis Edward S.
Published: January 2005

The effect of substituents on the rate of a reaction and the effect of the same substituents on the equilibrium can often be related by a linear free energy relation (LFER): log k− = α log K= + constant, where k+ and K= are the rate constant and the equilibrium constant, respectively. This review, concentrating on group transfers, adds to many studies describing the use of α to describe the transition state. Although the use of α to describe transition states is general, group transfers constitute a simple class allowing a fairly complete description yet illustrating two often neglected contributions. Group transfers can be described by the Marcus equation relating rate to an average identity rate and the equilibrium constant; a major contributor to the slope, α, of the rate‐equilibrium LFER is the variation of identity rates with substituent, rather than reflecting product‐like character. Substituent effect LFERs are predominantly attributable to interaction of charges with the substituent. However, α is not an exact measure of the charge on the substituent‐containing group, because in a transition state, but often not in a reaction product, there are more remote centers of charge which exert a smaller attenuated effect. A simple treatment of this attenuation for group transfers is proposed. The possibility of application of these ideas to proton transfer reactions and the interpretation of the Brønsted α (or β) is proposed.
Hydration of 2,2‐dichloro‐1‐arylethanones in water and tetrahydrofuran–water mixtures
Authors: Wendhausen Renato , Zampirón Eduardo , Vianna José F. , Zucco César , Rezende Marcos Caroli , Nome Faruk
Published: January 2005

The hydration of 2,2‐dichloro‐1‐arylethanones was studied in water and tetrahydrofuran (THF)–water mixtures and the equilibrium constants in water were estimated for four ethanones. The process is subject to specific acid and to general base catalysis. The proton inventory technique was applied to the study of the reaction in L2O and THF–L2O solutions (L = H or D). In pure water and water‐rich mixtures, a very large number of protons participate in the open transition state, this number decreasing gradually with increasing water content in the mixture, until the minimum value of 2 is reached, corresponding to a cyclic, closed transition‐state structure.
Consecutive radical ion pairs in the cycloreversion of a dimethylindene dimer: A case of cooperative spin polarization effects
Authors: Roth Heinz D. , Hutton Richard S.
Published: January 2005

Nuclear spin polarization effects observed during the electron transfer‐induced cleavage of the trans head‐to‐head dimer of 3,3‐dimethylindene are incompatible with the intermediacy of a single dimer radical cation. Instead, they are compatible with the ‘cooperative’ involvement of a localized, doubly linked and a delocalized, singly linked dimer radical cation. The mechanistic consequences for the cycloaddition and cycloreversion of radical cations are discussed.
Stereochemical studies. XXXIV. Quantitative description of ring puckering via torsional angles. The case of six‐membered rings
Authors: Zefirov N. S. , Palyulin V. A. , Dashevskaya E. E.
Published: January 2005

The quantitative description of ring puckering suggested by the authors is compared with that of Cremer and Pople. The applicability of both methods is discussed for the case of six‐membered rings with the use of model calculations simulating various ring distortions and with the analysis and comparison of puckering parameters computed on the basis of x‐ray data for 40 six‐membered rings in different cyclic structures. The 2N times reduction of the field of variation of puckering parameters for the N‐membered ring is suggested and the algorithm for the renumbering of the ring atoms for this purpose is described for six‐membered rings.
Electron distribution in the molecule of nitrones
Authors: Exner Otto
Published: January 2005

Vector analysis of dipole moments of two series of nitrones revealed a mesomeric dipole moment compatible with a relatively great contribution of a zwitterionic structure and possible some contribution from a hypervalent structure. The latter was also suggested from a detailed comparison of bond lengths among several classes of compounds, involving the CNO grouping. Since both the CN and NO bonds seem to possess an appreciable double bond character, it is suggested that the N atom might be allocated more then eight valence electrons.
Photochemical electrocyclization of the allyl radical into the cyclopropyl radical
Authors: Holtzhauer K. , Cometta‐Morini C. , Oth J. F. M.
Published: January 2005

Following the observation that allyl radicals trapped in an argon matrix can be photolytically converted into cyclopropyl radicals (λ = 410 nm, 18 K), the IR spectrum of the cyclopropyl radical was recorded for the first time and interpreted. Bicyclopropane and cyclopropane are formed when the photolysed argon matrix is warmed from 18 to 35 K. The identification of these new species unequivocally proves the presence of cyclopropyl radicals in the photolysed matrix. This radical is shown to be a σ‐type (Cs symmetry) and not a π‐type (C2v symmetry) radical; of the 18 normal frequencies of the Cs cyclopropyl radical, all active in the IR, 16 were observed and were assigned to their corresponding normal modes. For this assignment advantage was taken of ab initio frequency computations reported in the literature and performed by the authors.
Contrasting kinetic behaviour of allyl and crotyl alcohols towards N‐bromosuccinimide in aqueous methanol
Authors: Karunakaran C. , Ganapathy K.
Published: January 2005

The reactions of N‐bromosuccinimide (NBS) with allyl and crotyl alcohols in aqueous methanol are first order in NBS. Allyl alcohol displays a zero‐order dependence whereas crotyl alcohol exhibits a Michaelis–Menten‐type dependence on substrate concentration. The NBS–allyl alcohol reaction is inhibited by H+ whereas the NBS–crotyl alcohol reaction is independent of [H+]. However, both are fast in the absence of acid. The rates are unaffected by the addition of neutral salt and succinimide. The reaction of NBS with crotyl alcohol exhibits a positive dielectric effect whereas allyl alcohol displays no such effect. Inhibition by HgII is observed in the crotyl alcohol reaction but not with allyl alcohol. 3‐Bromo‐2‐methoxypropan‐1‐ol is the product of the allyl alcohol reaction but a mixture of 2‐bromo‐3‐methoxybutan‐1‐ol and 2‐bromobutane‐1,3‐diol in the crotyl alcohol reaction. In the allyl alcohol reaction the formation of solvated bromonium ion and of HOBr is suggested as rate‐limiting steps. In the crotyl alcohol reaction, rate determining breakdown of an NBS–crotyl alcohol complex, formed in a fast pre‐equilibrium, is proposed.
Photostimulated reactions of haloarenes with benzeneselenate ions by the SRN1 mechanism. Competition between electron transfer and fragmentation of radical anion intermediates
Authors: Pen̆én̆ory Alicia B. , Rossi Roberto A.
Published: January 2005

The photostimulated reaction of p‐iodoanisole (p‐IAn) and 2‐bromopyridine with PhSe− ions in liquid ammonia gave Ph2Se, ArSePh and Ar2Se (Ar = p‐anisyl, 2‐pyridyl) by the SRN1 mechanism. These products are formed due to the competition between two steps of the proposed mechanism, the fragmentation of the radical anion intermediate formed in the coupling of aryl radicals with the PhSe− ion, and the electron transfer from the radical anion to an electron acceptor. These photostimulated reactions were carried out in different solvents in order to study their influence on the rates of the two competing reactions. They were also studied at high concentrations of p‐haloanisoles in acetonitrile (ACN), and it was found that the straightforward substitution product AnSePh was formed only at a 2.5 M concentration of p‐IAn, 7·8 M p‐BrAn and 15·6 M p‐ClAn. The last compound did not react with the PhSe− ion at concentrations as high as 15·6 M, but the substitution reaction took place in the presence of 0·025 M p‐IAn (entrainment reaction). The relative reactivity of PhSe− vs PhS− toward 2‐quinolyl radicals was studied and it was found that PhSe− reacts 2·7 times faster than PhS− in ACN.
Mechanism of α‐substitution reactions of acrylic derivatives
Authors: Hill Jon S. , Isaacs Neil S.
Published: January 2005

Reactions between acrylic esters, nitriles and similar compounds on the one hand and aldehydes and ketones on the other, catalysed by tertiary amines, lead to α‐(hydroxyalkyl)acrylic compounds. Evidence on the basis of kinetics, volumes of activation and of reaction, and kinetic isotope effects is presented to deduce a mechanism in which amine first undergoes Michael addition, the resulting enolate ion adds to the carbonyl compound in a rate‐determining step and finally base is eliminated. An analysis of the solvent effect on rates is also presented.
Destabilized carbenium ions: α‐Carbamoyl‐α,α‐dimethylmethyl cations
Authors: Wolf Rainer , Grützmacher Hans‐Friedrich
Published: January 2005

The formation and unimolecular reactions of the especially electron‐deficient α‐carbamoyl carbenium ions [(CH3)2CCONH2]+ (a1) and [(CH3)2CCON(CH3)2]+ (a2) have been studied by mass spectrometric techniques. The ions a are formed by electron impact‐induced dissociation from the relevant isobutyric amides α‐substituted by I, Br and Cl, respectively, but the carbonyl protonated methacrylamides b1 and b2 are cogenerated. A similar mixture of ions a and b is obtained by CI(CH4) of the corresponding methacyrlamides. The metastable ions decompose by the loss of CO exhibiting in particular a large kinetic energy release (KER) and by the elimination of NH3 and HN(CH3)2, respectively. It is shown that isomeric ions of structures a and b interconvert prior to decomposition and that the energy barrier separating the isomeric ions is small. Hence the kinetic stability of the tertiary α‐carbamoyl‐α,α‐dimethylmethylcations is reduced compared with other types of α‐acyl carbenium ions. This effect can be attributed to the increased proton affinity of the amide group.
Structural studies of halogen adducts of diorganyl chalcogenides in solutions by 1H, 13C, 77Se and 125Te NMR
Authors: Nakanishi Warō , Hayashi Satoko , Tukada Hideyuki , Iwamura Hiizu
Published: January 2005

1H, 13C, 77Se and 125Te NMR spectra were measured for several sulphides, selenides, tellurides and their halogen adducts to establish the criteria for distinguishing trigonal bipyramidal (TB) adducts from molecular complexes (MCs). TB formation caused large downfield shifts for methyl protons and methyl, ipso and para carbons of methyl and phenyl selenides and tellurides. Large downfield shifts (> 100 ppm) were also observed for selenium and tellurium by the formation of TB from the parent selenides or tellurides. The plots of the 125Te vs 77Se chemical shifts for a set of corresponding compounds gave a straight line with a slope of 1·74, showing that the linear relationship holds well for tellurides and selenides and their TB adducts examined in this work. Upfield shifts of the ipso carbons were characteristic of MC formation. The para carbon signals of MC appeared downfield relative to those of the parent selenides, although the shift values were not so large. The 77Se signals for MC shifted slightly downfield (⩽ 10 ppm). The dissociation constants for iodine adducts of dimethyl selenide and selenoanisole were determined. The MC structure of bromine adducts of sulphides is well demonstrated on the basis of the criteria set out. 1H and 13C NMR spectra of ethylbenzene and ethers were also recorded in the presence of iodine or bromine. However, their chemical shifts were the same as those in the absence of iodine or bromine, within experimental errors.
Structural studies of halogen adducts of some cyclic selenides and tellurides by 1H, 13C, 77Se and 125Te NMR. Evidence for the formation of molecular complexes of selenoxanthone and selenanthrene with bromine
Authors: Nakanishi Warō , Yamamoto Yasuhiro , Hayashi Satoko , Tukada Hideyuki , Iwamura Hiizu
Published: January 2005

1H, 13C, 77Se and 125Te NMR spectra were recorded for selenoxanthone (1a), telluroxanthone (2a), selenanthrene (3a), related compounds and their halogen adducts to elucidate the structure of the adducts in solutions. Although selenides react with bromine to give trigonal bipyramidal (TB) hypervalent complexes in general, 1a reacted with bromine to yield a molecular complex (MC). Its chlorine adduct was found to be a TB. The effective electronegativity of selenium in 1a may be modulated by conjugation with the strongly electron‐withdrawing carbonyl group. In the case of 2a, its halogen adducts were TBs. The structure of the bromine adduct of 3a was also demonstrated to be an MC from NMR data.
Ion association and reactivity of the alkali metal salts of alkanoic acids in dipolar aprotic solvents
Authors: Crescenzi Manuela , Galli Carlo , Mandolini Luigi
Published: January 2005

The effect of added alkali metal perchlorates on the rate of lactonization of ω‐bromoalkanoate ions was investigated in 99% dimethyl sulphoxide (four‐membered ring formation) and in dimethylformamide (DMF) (four‐ and sixteen‐membered ring formation). In all cases the effect of the added metal salts is rate depressing, as a result of the lower reactivity of metal ion‐associated species relative to the free ions. Ion‐pairing association constants were determined, but the reactivity of ion pairs were so low as to elude direct measurement in most cases. Evidence was also obtained for the formation of ion triplets with Li+ in DMF. The relevance of the present results in connection with the ‘caesium effect’ is briefly discussed.
Role of 2‐carboxyl substituent in the tautomerization between two equivalent enol forms of 3‐hydroxyphenalenone
Authors: Matsumiya Shigeki , Izuoka Akira , Sugawara Tadashi , Nakamura Nobuo
Published: January 2005

The interconversion between two equivalent enol forms of 3‐hydroxyphenalenone took place predominantly through a diketo form with a free energy of activation of ca 14 kcal mol−1 in DMSO solution determined by 125·8 MHz13C NMR measurement. On the other hand, the corresponding interconversion in 2‐carboxy‐3‐hydroxyphenalenone was not frozen on the time scale of 13C NMR spectroscopy down to −60°C. This acceleration in the interconversion rate of the latter may be interpreted by a double proton switching between the hydrogen‐bonded 2‐carboxyl and 3‐hydroxyenone moieties.
Viscosity and dielectric properties of liquid binary mixtures
Authors: Mazurkiewicz Józef , Tomasik Piotr
Published: January 2005

The stoichiometry of solvates formed in some binary solvent systems is presented and types of interactions in such systems are discussed based on changes in viscosity and dielectric properties.
Synthesis and chemistry of azolenines. Part 19. Basicities of some 2H‐ and 3H‐pyrroles and the remarkably large pKa′ of 2,2,3,5‐tetramethyl‐2H‐pyrrole
Authors: Lui Kon‐Hung , Sammes Michael P.
Published: January 2005

pKa′ Values are reported for two 2H‐pyrroles and their 3H‐pyrrole isomers. The latter have basicities of the same order as similarly substituted pyridines, whereas the former are 2–2·5 pK units more basic, 2,2,3,5‐tetramethyl‐2H‐pyrrole having a pKa′ of 8·40, close to that for 2‐aminoimidazole. Possible reasons are given.
Frequency‐dependent branching ratio in the infrared multiphoton photochemistry of diethyl carbonates
Authors: Farneth William E. , Thomsen Marcus W. , Beck Thomas L.
Published: January 2005

Unimolecular decomposition of 0·1 Torr of diethyl carbonate, diethyl‐d5 carbonate and diethyl‐d10 carbonate induced by irradiation with a CO2 TEA laser was investigated. In all cases only ethylene, ethanol and CO2 were obtained. In the case of diethyl‐d5 carbonate, both ethylene‐d4 and ethylene‐d0 were observed together with the corresponding isotopic variants of ethanol. The chemical branching ratio was determined as a function of irradiation frequency and laser fluence by analysis of the ethylene‐d0/ethylene‐d4 ratio. RRKM theory applied to the branching ratio data requires very different average energies for two sets of fluence and frequency conditions that give identical total yields.
Borohydride reduction of alkyl phenyl ketones within a reversed‐phase liquid chomatographic column
Authors: Jaeger David A. , Clennan Malgorzata Wegrzyn
Published: January 2005

The reductions of propiophenone and octanophenone to 1‐phenylpropan‐1‐ol and 1‐phenyloctan‐1‐ol, respectively, with sodium borohydride and tetrabutylammonium borohydride were performed on a reverse‐phase highperformance liquid chromatographic (HPLC) column of macroporous 10‐μm poly(styrene–divinylbenzene) undr HLPC conditions. In these reactions a lower concentration of tetrabutylammonium borohydride than of sodium borohydride was needed to effect the same extent of reduction, and modest substrate selectivity was obtained.