bluuebunny/crossref_metadata_2025 huggingface dataset:
Enantioselective synthesis of alkylidene cyclohexanes by an asymmetric olefination/cross‐coupling sequence
Authors: Denmark Scott E. , Chen Chien‐Tien
Published: January 2005

A general method for the preparation of dissymmetric olefins has been developed. The anion derived from an enantiomerically enriched P‐(phenylthiomethyl)phosphonamidate(1,3,2‐oxazaphosphorinane2‐oxide) was added to 4‐tert‐butylcyclohexanone with excellent diastereoselectivity. The β‐hydroxyphos‐phonamidate was converted into a (phenylthio)‐methylidene with excellent stereospecificity using a novel electrophile‐promoted olefination that employed trityl triflate and 2,6‐lutidine in warm acetonitrile. The vinyl sulfide underwent nickel‐catalyzed coupling with Grignard and dialkylzinc reagents to produce (S)‐4‐(tert‐butyl)alkylidenecyclohexanes with moderate to high stereospecificity.
Thermolysis, photolysis, and oxidation of an overcrowded 1,3,2‐dithiastannetane derivative
Authors: Tokitoh Norihiro , Stresing Verena , Matsuhashi Yasusuke , Okazaki Renji
Published: January 2005

Reactions of a sterically crowded 1,3,2‐dithiastannetane derivative bearing 2,4,6‐tris[bis(trimethylsilyl)methyl]phenyl (=Tbt) and 2,4,6‐triisopropylphenyl (=Tip) groups on the tin atom are described. Both thermolysis and photolysis of the 1,3,2‐dithiastannetane [Tbt(Tip)SnS2CPh2] resulted in the formation of products derived from the corresponding stannanethione [Tbt(Tip)Sn=S], while the oxidation reaction by m‐chloroperbenzoic acid gave a novel tincontaining heterocyclic system, an 1,2,4,5‐oxadithiastannolane derivative.
Synthesis and properties of a novel cyclic sulfilimine, 2‐methyl‐2,4,1‐benzodithiazin‐2‐ium‐1‐ide
Authors: Shimizu Hiroshi , Sugimoto Atsushi , Kataoka Tadashi , Hori Mikio
Published: January 2005

A novel cyclic sulfilimine, 2‐methyl‐2,4,1‐benzodithiazin‐2‐ium‐1‐ide (4) was synthesized by deprotonation of the corresponding azasulfonium salt (3) with base. The compound 4 was oxidized with potassium permanganate to afford the sulfoximine 5, exclusively. On refluxing in several solvents, compound 4 underwent a ring contraction to afford benzothiazole (8) via the 1,2‐imino shift. The reaction of 4 with a variety of electrophiles, such as dialkyl acetylenedicarboxylate, acylating agents, diphenylcyclopropenone, and phenyl isocyanate, afforded ringopened adducts. Synthetic approaches to cyclic disulfonium ylides are also described.
Investigation of the mechanism of reaction of S‐ethyl‐N,N′‐tetraethyldiamidothio‐phosphite with [C5H 5Mn(CO)2NO]+BF by fourier transform infrared spectroscopy
Authors: Plyamovatyi Alexandr Kh. , Mukhamadeeva Raviya M. , Milyukov Vasily A. , Sinyashin Oleg G. , Vandyukov Alexandr E. , Shagidullin Roald R. , Ginzburg Allan G. , Sokolov Vyacheslav I.
Published: January 2005

FT‐IR spectroscopy and a special mathematical program were used for the real‐time monitoring of the mechanistic path of the reaction of S‐ethyl‐N,N‐tetraethyldiamidothiophosphite with [CpMn(CO)‐2NO]+BF. The formation of a few intermediates is described.
Synthesis and reaction of selenocarbamic acid sodium and potassium salts and organo‐germanium, ‐tin, and ‐lead esters
Authors: Kato Shinzi , Kawachi Toshiaki , Ibi Kazumasa , Nakaiida Shoho , Kawai Kohji , Kanda Takahiro , Murai Toshiaki , Ishihara Hideharu
Published: January 2005

Sodium 2 and potassium selenocarbamates 3 were found to be synthesized in moderate to good yields by the reaction of carbamoyl chlorides with sodium and potassium selenides. The salts 2 and 3 reacted with alkyl halides and organo‐germanium, ‐tin, and ‐lead chlorides to give the corresponding esters 7–9 in good yields.
Reactions of diselenoic acid esters with amines and X‐ray crystal structure analyses of aromatic selenoamides
Authors: Murai Toshiaki , Mizutani Tomoyoshi , Kanda Takahiro , Kato Shinzi
Published: January 2005

Aromatic diselenoic acid Se‐methyl esters 1 react with amines at 0°C in tetrahydrofuran (THF) to yield selenoamides in moderate to good yields. The reaction course is highly dependent on the steric requirements of both starting materials. In the reactions of the ester 1a with 2‐methylpiperidine and of the ester 1b with piperidine, the starting materials disappear within 1 hour with the liberation of black selenium, but the corresponding selenoamides are not produced. These results may be ascribed to the steric congestion caused by the formation of the selenoamide group from the tetrahedral intermediate 15. X‐ray crystal structure analyses of the selenoamides 3 and 9 have been performed. The bond length of C(Se)N is shorter than a carbon nitrogen single bond. On the other hand, the CSe bond is longer than that of the ordinary carbon‐selenium double bond. These results are indicative of the efficient delocalization of the electrons of nitrogen to the carbon–selenium double bond. The double bond character between the carbon attached to selenium and the nitrogen is also supported by the nitrogen atom showing sp2 character. When a methyl group is introduced at the meta position of the aromatic ring, the deviation of the aromatic ring from the plane involving the carbon–selenium double bond and nitrogen atom becomes substantially large, perhaps due to the steric bulkiness of the selenium atom.
Facile synthesis of some novel pyrrole and pyridazinoquinazolone derivatives
Authors: Kandeel Zaghloul E. , Farag Ahmad M. , Abdelrazek Fathy M.
Published: January 2005

3‐Dicyanomethylene‐3‐phenylpropionitrile coupled with diazotized aromatic amines (Ar‐NH2) to afford hydrazono derivatives. The latter (Ar = C6H5, 4‐CH3C6H4, 4‐CH3OC6H4, and 4‐ClC6H4) were readily cyclized upon reflux in aqueous NaOH to 3(2H) pyridazinimine derivatives, which were readily transformed into their corresponding pyridazinone derivatives on reflux in ethanolic HCl. The pyridazinimines undergo reductive cleavage and recyclization via loss of ammonia to afford the corresponding N‐aryl pyrroles on reflux in glacial acetic acid with Zn dust. The pyridazinone derivatives, however, undergo the same reaction but with loss of the aromatic amine moiety to afford only one pyrrolone derivative. The hydrazono derivative (Ar = 2‐NCC6H4) was cyclized into pyridazino[3,2‐b]quinazolin‐6‐imine, which is easily converted into pyridazino[3,2‐b]quinazolin‐6‐one on reflux in ethanolic HCl. The latter compound is also obtained from the hydrazo derivatives (Ar = 2‐HOOCC6H4 and 2‐MeOOCC6H4) by reflux in aqueous NaOH.
Activated nitriles in heterocyclic synthesis: Novel syntheses of 3H‐1,2,4‐triazolo‐[1,5‐a]pyridine derivatives
Authors: Aziz Suzan I. , Kandeel Zaghloul E. , Husein Mona M. , Gohary Salem El , Abou El Maged Eiman I.
Published: January 2005

A new route for the synthesis of 3H‐1,2,4‐triazolo[1,5‐a]pyridines 7a–j, 12a,b, and 17a,b utilizing the reaction of the hydrazones of cyanoethanoic acid hydrazide 3a,b with ylidene malononitriles 2a–e, malononitrile, and 3‐aminocrotononitrile is described.
Radical reduction of cyclic xanthates: Formation of alkenes and/or 1,3‐oxathiolanes from 1,3‐oxathiolane‐2‐thiones
Authors: Uenishi Jun'ichi , Kunugi Takayuki , Kubo Yuki
Published: January 2005

AIBN‐initiated radical reactions of 5‐membered cyclic xanthates, 1,3‐oxathiolane‐2‐thiones, with tributyltin hydride are described. Alkenes are formed at 0.025 M concentration of tributyltin hydride, whereas a higher concentration (0.25 M) gives 1,3‐oxathiolanes. A mixture of alkene and 1,3‐oxathiolane is obtained by use of intermediate concentrations. Reactions of cis‐and trans‐4,5‐dialkyl‐1,3‐oxathiolane‐2‐thiones with tributyltin hydride afford E‐alkenes stereoselectively. For an application of this alkene formation reaction, geraniol has been converted to linalool silyl ether in good yield.
Reactions of 3,5‐diethoxycarbonyl 1,2,4‐diazaphospholes and arsoles with alkyl vinyl ethers, sulfur ylides, and diazocompounds
Authors: De Dianous Patricia , Himdi‐Kabbab Souad , Hamelin Jack
Published: January 2005

3,5‐Diethoxycarbonyl 1,2,4‐diazaphospholes and arsoles undergo N‐alkylation by reaction with alkyl vinyl ether, sulfur ylides, and diazocompounds, owing to the acidity of the NH group. © 1995 John Wiley & Sons, Inc.
Syntheses and characterization of pentacoordinate organo‐tin(IV) complexes II
Authors: Wang Ji‐Tao , Zhang Yun‐Wen , Xu Yu‐Ming , Wang Zhi‐Wen
Published: January 2005

Nine substituted benzoyl hydrazonyl, three semicarbazonyl, and four thiosemicarbazonyl tridentate ligands were synthesized. They were used to coordinate with Bu2SnCl2 or (PhCH2)2SnCl2 to form 18 novel tin complexes that contained pentacoordinate organotin(IV) in a heterobicyclic ring. All these complexes were characterized by MS, NMR, and IR spectroscopy elemental analyses. © 1995 John Wiley & Sons, Inc.
New method for the synthesis of 3(2H)‐pyridazinones and their alkene precursors: Solvent‐free reactions under microwave irradiation
Authors: Jolivet Sandrine , Texier‐Boullet Françoise , Hamelin Jack , Jacquault Patrick
Published: January 2005

Several 3(2H)‐pyridazinones4were prepared from monophenylhydrazones of 1,2 dicarbonyl compounds1and various active methylene compounds2within 1−15 minutes, without solvent, under microwave irradiation, in the presence of carefully adjusted amounts of piperidine or solid potassium t‐butoxide. The intermediate alkenes3were successfully prepared in several cases. © 1995 John Wiley & Sons, Inc.
Molecular and electronic structure of benzeneselenenyl molecules and cations
Authors: BelBruno Joseph J.
Published: January 2005

Molecular and electronic structures of a select group of molecules and cations, including benzeneselenenyl chloride, benzeneselenenyl bromide, and benzeneselenol have been studied using ab initio calculations at the Hartree–Fock and MP2 levels of theory. Very few experimental data are available for this class of compounds. The properties and structures of these molecules are compared. © John Wiley & Sons, Inc.
Synthesis of diphosphine dioxides for extraction of actinides using supported liquid membranes technology
Authors: Cristau Henri‐Jean , Mouchet Patrick , Dozol Jean‐François , Rouquette Hélène
Published: January 2005

A recurrent method for synthesis of diphosphine dioxides to be used for extraction of actinides from acidic aqueous solution is described. Selective phosphonium salt formation and cleavage permits the stepwise introduction of different bridges between the phosphorus atoms as well as various chains on them. The influence of the structural parameters on liquid‐liquid extraction properties of plutonium, neptunium, and americium is studied. Plutonium and neptunium can be efficiently removed from radioactive contaminated liquid wastes, using the supported liquid membranes technology with the more lipophilic organophosphorus extractants. © John Wiley & Sons, Inc.
X‐Ray spectral determination of the effective charges on phosphorus, sulfur, and chlorine atoms in chemical compounds with a nonempirical charge scale
Authors: Dolenko G. N. , Latajka Z. , Ratajczak H.
Published: January 2005

Linear dependence between the experimental Ka line shifts and Mulliken atomic charges obtained by SCF ab initio calculations with 4‐31G, 4‐31G*, and 4‐31G** basis sets for the P, S, and Cl atoms have been found. The electron density redistribution of PCl3 and SPCl3 free ligands on their complexation with AlBr3 has been investigated. It has been shown that a significant transfer of the total ligand electron density to the acceptor is absent, but there is an essential growth of the ionicity of all bonds on complexation. The P = S and PS bond ionicities are found to increase linearly with the growth of the positive charge on the central phosphorus atom. © John Wiley & Sons, Inc.
Pyrazoline derivatives: A convenient synthetic route to new pyrazolo‐benzothia‐(oxa) or diazepinone derivatives
Authors: El Latif Fawi M. Abd
Published: January 2005

New pyrazolo‐[3,4‐b]‐[1,5]‐benzoazepinone derivatives are reported. One pot reactions of 5‐chloro‐4‐carboxy‐1‐phenyl (3‐substituted) pyrazole derivatives with o‐thioaminophenol, o‐phenylenediamine, and o‐aminophenol derivatives were realized. The influences of the polarizability of the heteroatoms on the reaction rates and chemical yields are discussed. © John Wiley & Sons, Inc.
3‐Silanyl‐propenylphosphonates: Properties and alkylation potential
Authors: Probst Michael F. , Modro Tomasz A.
Published: January 2005

Two 3‐silanyl‐propenylphosphonate esters (1a, 1b) were synthesized, and their deprotonation was attempted using RONa/ROH, RLi/THF, and LDA/THF systems. In the first two cases, the nucleophilic addition was the predominant (or exclusive) reaction observed; deprotonation was achieved with LDA, as confirmed by the reaction of the lithiated species with alkylating agents and with benzaldehyde. Chemical behavior of substrates 1 does not parallel closely that of the parent silanyl or phosphoryl‐substituted allylic systems. © John Wiley & Sons, Inc.
Studies with polyfunctionally substituted heteroaromatics: 2‐Phenyl‐4‐p‐tolylhydrazono‐2‐oxazoline‐5‐one as a precursor for the synthesis of substituted 1,2,4‐triazoles and pyridines
Authors: Elnagdi Mohamed Hilmy , Negm Abdalla Mohamed , Erian Ayman Wahba , El‐Kousy Salah
Published: January 2005

2‐Phenyl‐4‐p‐tolylhydrazono‐2‐oxazoline‐5‐one (3) was rearranged by the action of phenols and naphthols into 1,2,4‐triazole‐5‐carboxylic esters (5) that were rearranged further on reflux in AcOH‐ZnCl2 into triazolyl ketones (7). Rearrangement of 3 into 1,2,4‐triazole derivatives could also be effected by the action of heterocyclic amines and 1‐naphthylamine. © John Wiley & Sons, Inc.
Stereostructure of 8‐chloro‐5,6‐di(methoxycarbonyl)‐4,7‐dimethyl‐2‐ethoxy‐2‐phosphabicyclo[2.2.2]octa‐5,7‐diene 2‐oxide
Authors: Keglevich György , Tőke László , Böcskei Zsolt , Menyhárd Dóra , Quin Louis D.
Published: January 2005

The first X‐ray structure of a phosphabicyclooctadiene, together with the NMR and mass spectral characterization of its isomers, is reported. © John Wiley & Sons, Inc.
Fluorsulfonylmethylidene sulfur difluoride oxide, FSO2CH  SF2  O
Authors: Henkel Thomas , Seppelt Konrad
Published: January 2005

SO3 adds across the CS double bond of H2C  SF4 with formation of 2‐tetrafluoro‐4‐dioxo‐1,2,4‐oxadithietane, which rearranges to fluorsulfonylmethylidene sulfur difluoride oxide, FSO2CH  SF2  O in the presence of CsF. © John Wiley & Sons, Inc.
Geminal conjugation in disulfides
Authors: Dolenko G. N. , Deryagina E. N. , Turchaninova L. P. , Elin V. P. , Basina E. I. , Pavlova T. O. , Voronov V. K.
Published: January 2005

Some aspects of the spatial and electronic structure of disulfides XSSX (X = H, Alk, Ph, Hal) are considered. It is shown that the growth of the geminal ns‐σSX* conjugation efficiency leads to a shortening of the SS bond that is more than three times as large as the simultaneous SX bond lengthening. The positive effective charge on the sulfur atom also increases as a result of this conjugation. These effects increase with the growth of ‐ I and + M abilities of the substituents X. The SKa line shifts and the HOMO bonding degree (Delta;nS) have been measured by the X‐ray fluorescence spectroscopy method for dialkyl disulfides (Alk = Me, Et, Pr, i‐Pr, Bu, i‐Bu, t‐Bu, C5H11, C8H17, H2NCH2CH2, CH2CH  CH2, CH2Ph) and S8. With the help of ΔnS values that are proportional to the nS–σSC* conjugation efficiency, the sequence of the enhancement of the geminal conjugation efficiency has been established for the disulfides investigated. In the framework of the nS–σSS* geminal conjugations, the shortening of the SS bonds in S8 is explained. © John Wiley & Sons, Inc.
Protein–protein interactions of a Kvβ subunit in the cochlea
Authors: Sokolowski Bernd , Harvey Margaret , Venkataramu Chinnambally , Duzhyy Dmytro
Published: January 2005

Accessory subunits associated with voltage‐gated potassium (Kv) channels can influence the biophysical properties and promote the surface expression of channel‐forming α‐subunits. Previously, we cloned several α‐subunits and a β‐subunit from a cDNA library of the chicken cochlea. In the present study, we raised an antibody against the N‐terminus of chicken Kvβ1.1 (cKvβ1.1) and characterized the Kvβ‐related polypeptide in cochlear tissues and heterologous cells. The anti‐cKvβ1.1 antibody recognizes a 45‐kDa polypeptide in chick cochlear extracts as well as in Chinese hamster ovary (CHO) cells transfected with cKvβ1.1. The accessory subunit was localized to the ganglion cells of the chick cochlea using immunohistochemistry and in situ hybridization. Coimmunoprecipitation studies show that Kvβ1.1 interacts with Shaker channel members Kvα1.2 and 1.3, both of which colocalize with β to the cochlear ganglion cells. Additionally, coimmunoprecipitation studies show that Kvα1.2 and 1.3 interact with each other, suggesting that these ion channels are formed by heteromultimers. In comparison, Kvβ did not coprecipitate with a member of the Shal subfamily. The presence of Kvβ in the cochlea suggests that this subunit contributes to the modulation of auditory signals in the ganglion cells, presumably by regulating properties of inactivation as well as surface expression of Kvα channels. © 2005 Wiley‐Liss, Inc.
Relaxation of drawn Nafion films studied with birefringence experiments
Authors: Heijden P. C. van der , Rosa A. de la , Gebel G. , Diat O.
Published: January 2005

The time dependency of the birefringence and stress of a drawn Nafion film is measured. From shrink and free relaxation experiments, the existence of a reversible regime at small draw ratios and an irreversible regime at large draw ratios is shown. In the frame of a structural model of Nafion as a fibrillar system that has been recently proposed, the existence of bundles of fibrils is used to explain both regimes. Copyright © 2005 John Wiley & Sons, Ltd.
Induced surface migration of biodegradable phosphoryl choline functional poly(trimethylene carbonate)
Authors: Nederberg Fredrik , Bowden Tim , Hilborn Jöns
Published: January 2005

In this article the synthesis, characterization, and surface orientation property of a biodegradable and biomimetic polymer are introduced. This phospholipid mimetic biodegradable polymer is synthesized by combining poly(trimethylene carbonate) (PTMC) with zwitterionic phosphoryl choline (PC) in a three‐step synthesis. Since the glass transition of the polymer is around −20°C this material holds elastic properties at ambient temperature. This characteristic was used to induce surface enrichment as the polar PC end‐group was enriched at the surface while treating films in an aqueous media. Film properties of the PTMC‐PC amphiphile product revealed surface enrichment behavior, as the polar PC head group is oriented towards the surface. In addition, surface depletion of polar PC groups was the result when treating films under vacuum. This was observed by both contact angle measurements and electron spectroscopy for chemical analysis (ESCA) analysis. Copyright © 2005 John Wiley & Sons, Ltd.
Radiation polymerization and concentration separation of P(NIPA‐co‐AMPS) hydrogels
Authors: Zhuang Yinfeng , Wang Guowei , Yang Hua , Zhu Zhongqi , Fu Jianwei , Song Weiqiang , Zhao Huidong
Published: January 2005

Extraction or concentration with temperature‐sensitive hydrogels is a novel separation technology. In this study, N‐isopropylacrylamide (NIPA) was synthesized by acrylonitrile and isopropanol. Poly(N‐isopropylacrylamide) (PNIPA) and copolymer of NIPA and 2‐acrylamide‐2‐methylpropane sulfonate [P(NIPA‐co‐AMPS)] hydrogels were prepared by radiation polymerization. Dependence of their swelling behavior on temperature was studied. Effects of radiation dose on polymerization, feed composition on thermoresponse, electrolyte on relative swelling ratio, and swelling and deswelling kinetics were investigated. The experimental results showed that P(NIPA‐co‐AMPS) hydrogels with low content of AMPS/NIPA (1–5 %), prepared at a radiation dose‐rate of 1 kGy/h and total dose of 30–40 kGy, could enhance the swelling ratio of PNIPA hydrogels significantly and raise the phase‐transition temperatures. P(NIPA‐co‐AMPS) hydrogels produced under optimum conditions were used to concentrate aqueous bovine serum albumin (BSA, M = 69 000 g mol−1) solution. When aqueous BSA concentration was below 5 %, the separation efficiency was more than 80 % with low cost and low energy consumption. Copyright © 2005 Society of Chemical Industry
Synthesis and characterization of novel multifunctional poly(methyl methacrylate)s as potential fluorescent labels for electron‐beam lithography
Authors: Liao Shaowen , Soo Choi Pheng , Ye Huanwen , Valiyaveettil Suresh
Published: January 2005

A series of novel fluorophore‐rich polymers has been synthesized with the aim of developing radiation‐sensitive materials as electron‐beam resists. The polymers were characterized using FTIR and NMR spectroscopy, and gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis measurements. These polymers showed strong absorbance in the region of 330–380 nm, and can be patterned by an electron‐beam in their pure form or mixed with other components. All polymers also generated intense emission in the range 510–565 nm when irradiated by a laser source operating at a wavelength of 488 nm. The sensitivity of the polymeric fluorescence label as an electron‐beam resist was also discussed. Moreover, through immobilization of the fluorophores onto a polymer backbone, we managed to avoid the crystallization of fluorophores inside the polymer film. Copyright © 2005 Society of Chemical Industry
Fatigue resistance of silica‐filled natural rubber vulcanizates: comparative study of the effect of phosphorylated cardanol prepolymer and a silane coupling agent
Authors: Menon ARR , Pillai CKS , Jin WS , Nah C
Published: January 2005

The fatigue resistance of silica‐filled natural rubber (NR) mixes modified with phosphorylated cardanol prepolymer (PCP) was studied in comparison with similar compositions without PCP and with those containing the same dosage of a silane coupling agent (Si‐69). Considerable improvement in the fatigue resistance was observed for the PCP‐modified NR vulcanizate containing 20 phr of silica compared with the unmodified and Si‐69 modified vulcanizates. In addition, the tear strength of the PCP‐modified NR vulcanizate was higher than that of the others. Atomic force microscopy and the scanning electron microscopy of the vulcanizates showed better dispersion of silica particles in the NR matrix in the presence of PCP than in the unmodified and Si‐69‐modified NR vulcanizates. It is assumed that, at a dosage of 5 phr, PCP functions as a coupling agent between NR and the silica particles thereby improving the filler dispersion and consequently the mechanical properties of the vulcanizate. Copyright © 2005 Society of Chemical Industry
X‐ray diffraction studies and phase volume determinations in poly(ethylene glycol)–montmorillonite nanocomposites
Authors: Chen Biqiong , Evans Julian RG
Published: January 2005

Poly(ethylene glycol)–montmorillonite nanocomposites were prepared by both solution and melt intercalation methods with a range of polymer molecular weights and at a range of polymer loadings. Particular attention was given to the reliability of low‐angle X‐ray diffraction results for basal plane spacing and a sound correlation between three diffractometers was obtained (±0.005 nm). Expansion of the basal plane spacing from 1.23 nm to 1.82 nm by solution intercalation was independent of polymer molecular weight in the range 300–20 000. Furthermore, the clay expansion was independent of the method of intercalation; melt intercalation also gave d001 = 1.82 nm irrespective of polymer molecular weight. The maximum amount of polymer intercalated by clay and the maximum loading of clay that polymer can sustain were also studied for the determination of nanocomposite formulations. The confined polymer exerts a reduced effective density (670 kg m−3) in the galleries. Copyright © 2005 Society of Chemical Industry
Circular dichroism of In‐Situ trinuclear organotransition metal complexes with optically active ligands
Authors: Barton Derek H. R. , Frelek Jadwiga , Snatzke Günther
Published: January 2005

Several Cotton effects are developed within absorption bands of trinuclear organotransitionmetal complexes in the presence of acids, diols, amines and aminoalcohols even in the case of bulky substituents on nitrogen; with monohydroxy compounds no circular dichroism could be detected.
Study on 5, 15‐dialkylporphyrins interconversion between two conformers in solution
Authors: Maruyama Kazuhiro , Nagata Toshi , Osuka Atsuhiro
Published: January 2005

Novel structural features of 5, 15‐dialkylporphyrins in solution are described. The 1H‐NMR spectra of these compounds showed broad signals at room temperature, which split into two sets of signals at lower temperatures. This unusual phenomenon was ascribed to a dynamic interconversion between tow distorted structures. The 5, 15‐dialkylporphyrin has a distorted ring due to the steric hindrance between the 5(or 15)‐alkyl group and the 3, 7(or 13, 17)‐alkyl groups and, depending on the position of the 5, 15‐alkyl groups relative to the average ring plane, can exist in two conformations; syn (where the two alkyl groups are on the same side of the ring plane) and anti (on the opposite sides). Preliminary kinetic study of this interconversion using the NMR line shape analyses is also reported.
Photocyclization of N‐Alkyl‐N‐(3‐aryl‐3‐butenyl) ureas. Hydrogen transfer via charge transfer exciplexes in alkene photochemistry
Authors: Aoyama Hiromu , Tomohiro Takenori , Arata Yoshiaki , Omote Yoshimori
Published: January 2005

Photolysis of N‐alkyl‐N‐(3‐aryl‐3‐butenyl) ureas (1) in acetonitrile gave cyclization products, 3‐aryl‐3‐methyl‐pyrrolidines, in good yields, whereas irradiation of 1 in methanol afforded methanol adducts as well as the cyclization products. Both the reactions are singlet reactions, and the cyclization is presumed to proceed via 1,6‐hydrogen transfer from exciplexes with charge transfer character.
Concerning the weakness of intramolecular general acid catalysis in the hydrolysis of vinyl ethers. o‐carboxy‐α‐methoxy‐β,β‐dimethylstyrene
Authors: Kresge A. J. , Yin Y.
Published: January 2005

The rate of hydrolysis of the aromatic vinyl ether o‐carboxy‐α‐methoxy‐β,β‐dimethylstyrene was found to be accelerated 25‐fold by ionization of its carboxylic acid group, but the effective molarity which may be calculated if all of this rate acceleration is ascribed to intramolecular general acid catalysis is only EM = 1 · 1 m. This is similar to the small effective molarities found before for intramolecular catalysis by carboxylic acid groups of aliphatic vinyl ethers, which shows that, unlike the situation in other intramolecular reactions, e.g. ketone enolization, the extra rigidity of aromatic over aliphatic systems does not improve the efficiency of intramolecular catalysis in vinyl ether hydrolysis.

It is suggested that this behaviour is the result of reduced conjugation between the vinyl ether group and the aromatic ring in the transition state of the vinyl ether hydrolysis reaction, which retards the rate and offsets any improvement effected by increased rigidity of the aromatic system.
The lone‐pair orbitals of triaziridine
Authors: Kaupp Gerd , Döhle Jens A. , Burger Klaus , Rademacher Paul , Poppek Rainer
Published: January 2005

The PE spectra of four stable bicyclic triaziridines with trifluoromethyl, methyl, phenyl, spirocyclopentane and spirocyclohexane substituents are measured. From a comparison of these experimental data with MNDO calculations the energies and the interactions of the nitrogen lone‐pair orbitals were obtained. The trifluoromethyl group may be reliably simulated by a fluorine atom. The ionization potentials are unexpectedly high and so are the cyclovoltammetric anodic potentials. The MNDO valence electron densities are in agreement with the comparatively small differences in the chemical shifts of the differently substituted nitrogens of the triaziridine rings.
Syntheses, spectroscopic characterization and electronic structure of cyclopropenylidene ligated platinum complexes
Authors: Miki Sadao , Ogno Toshinobu , Iwasaki Hideaki , Yoshida Zen‐Ichi
Published: January 2005

New series of platinum complexes of cyclopropenylidenes of the types of PtX2(CP)2 and trans‐PtX(PBu3)2(CP) have been synthesized, where CP is di‐t‐butylcyclopropenylidene (BCP) or bis(diisopropylamino)cyclopropenylidene (ACP). The 13C‐NMR chemical shifts, and 13C−195Pt coupling constants (1JPtC) for the complexes are discussed in comparison with those values derived from closely related series of compounds, trans‐PtCl(PR3)2L; L  CH3, C6H5 and CCBu‐t. An excellent linear relationship through the origin was obtained between 1JPtC and the formal ‘s’ % character of the carbon directly bonded to Pt for the series trans‐PtCl(PR3)2L in which the PtC bond is regarded as a pure σ‐linkage, whereas 1JPtC deviates largely from this relationship when pπdπ bonding interaction possibly exists in the PtC bond. The NMR data suggest the strong nmr trans‐influence of the cyclopropenylidenes and that in the PtCP bond the σ‐interaction is appreciable but the π‐interaction is negligible.
The solvatochromic equation and insight into chemical reactivity
Authors: Harris J. Milton , Sedaghat‐Herati M. R. , McManus Samuel P. , Abraham M. H.
Published: January 2005

Reaction rates for solvolysis of a mustard analogue are accurately correlated by the solvatochromic equation without inclusion of a nucleophilicity term, and thus the equation is shown to reveal mechanistically significant information.
Studies on organophosphorus compounds XXXII. A molecular mechanics study of the hydrolytic reaction of alkylphosphonates and alkylphosphonyl chlorides
Authors: Li Shusen , Liao Xiugao , Yuan Chengye
Published: January 2005

The alkaline hydrolysis of several alkylphosphonates and alkylphosphonyl chlorides has been investigated by molecular mechanics calculations (MM2, 1985 version). The difference of the steric energies (ΔE) between tetracoordinate substrate and pentacoordinate transition state of phosphorus compounds represents the activation energy (ΔE≠) in hydrolysis. The change of ΔE for various alkyl groups relative to methyl group (ΔΔER) is suggested as a measure of the steric effect of substituents. Thus the correlation analysis involving log k and ΔΔER of the branched alkyl group gives good results and it is reasonable to anticipate that analogous treatment using ΔΔER for the straight chain alkyl group is not satisfactory owing to the minor contribution of steric effect of the latter. However, the multiple regression analysis of log k with ΔΔER and Taft's σ* provides very good results. As shown by us, for the hydrolytic reactions studied, the proposed ΔΔER is much better than Taft's Es and Charton's ν, the commonly used well‐known steric parameters in the chemistry of carbon compounds.
General base catalysis of photo‐smiles rearrangement of 1‐(4‐nitrophenoxy)‐2‐anilinoethane in aqueous solution. Identity of the proton‐donating intermediate
Authors: Wubbels Gene G. , Sevetson Bradley R.
Published: January 2005

4‐O2NC6H4OCH2CH2NHPh undergoes clean base‐catalyzed Smiles photorearrangement to 4‐O2NC6H4N(Ph)CH2CH2OH in dimethyl sulfoxide–water (25:75). A linear plot of ϕ−1 vs [OH−]−1 indicated that the limiting quantum yield at high [OH−] is 0·12 and that uncatalyzed photorearrangement does not occur. Rate constants for the deprotonation step were determined for a variety of bases having conjugate acid pKa values in the range 5–10. When plotted according to the Brønsted Catalysis Law, these data gave a non‐linear plot approaching slopes of zero and unity above and below a pKa of 6–7. This indicates that the proton‐donating intermediate in this photo‐Smiles rearrangement is the zwitterion diradical (pKa ≈ 7) rather than the Meisenheimer complex (pKa ≈ 2).
Long range electrical field effects in solvolysis and 13C‐NMR shielding of androstanes with halogen, hydroxy and oxo substituents
Authors: Schneider Hans‐Jörg , Becker Norman
Published: January 2005

The solvolysis of 21 different 3‐ or 17‐androstanyl tosylates or chlorides with halogen, hydroxy or oxo substituents in 17‐ or 3‐position shows rate constant variations in hexafluoro isopropanol of up to 6·3 with regular differences for epimeric substituents. Similar variations ae seen over a distance of ∼10 Å in 13C‐NMR shifts at C‐17‐ones of androstan‐17‐ones with varied halogen substituents in C‐3, whereas the shielding observed at other distant carbon atoms excludes significant through bond effects. It is shown how, on the basis of suitable Coulomb‐type equations and of force field minimized geometries, both the stability variation of carbocationic transition states and the carbonyl group polarization are predictable by linear electric field effects, using the same parametrization.
Theoretical study of pyrazole elimination of N‐alkyl pyrazoles
Authors: Perez Jorge D. , Phagouapé Leonardo M. , Davico Gustavo E.
Published: January 2005

The gas‐phase pyrazole elimination of N‐alkyl pyrazoles has been studied using MNDO semi‐empirical molecular orbital (MO) theory with complete geometry optimization of all stationary points. We found that the activation energies (Ea) of the concerted processes are around 80 kcal/mol, 25 Kcal/mol higher than experimental values. But the differences in Ea between compounds with different substituents are in good agreement with the experimental ones.
Hydrogen‐bonding. Part 4. An analysis of solute hydrogen‐bond basicity, in terms of complexation constants (log K), using F1 and F2 factors, the principal components of different kinds of basicity
Authors: Abraham Michael H. , Grellier Priscilla L. , Prior David V. , Morris Jeffrey J. , Taylor Peter J. , Maria Pierre‐Charles , Gal Jean‐Francois
Published: January 2005

The principal components factors F1 and F2 in the equation

have been used to obtain S1 and S2 values for sets of hydrogen‐bond bases against 32 reference acid/solvent systems. The constants S1 and S2 define an angle θ = tan−1 S2/S1 that is a measure of the electrostatic:covalent bonding ratio in the hydrogen‐bond complex. It is shown that θ can vary from 53 (4‐fluorophenol in CH2Cl2)to 86 degrees (Ph2NH in CCl4) depending on the reference acid and solvent. This variation in θ can lead to family dependent behaviour in plots of log K for bases against a given reference acid system vs log K for bases against another reference acid system, and precludes the construction of any general scale of hydrogen‐bond basicity using log K values. Amongst a quite wide range of reference acid/solvent systems θ varies only from 64 to 73 degrees, and for bases against these reference systems a ‘reasonably general’ scale could be set up. Such a scale could be extended to bases against reference acid/solvent systems outside the 64–73 degree range provided that certain classes of base (e.g. pyridines, alkylamines) were excluded from the additional reference acid/solvent systems.
Photostimulated reactions of neopentyl halides with nucleophiles by the SRN1 mechanism
Authors: Bornancini Esteban R. N. , Palacios Sara M. , Peñéñory Alicia B. , Rossi Roberto A.
Published: January 2005

The photostimulated reaction of neopentyl halides with different nucleophiles by the SRN1 mechanism of nucleophilic substitution has been studied. Neopentyl halides do not react with carbon nucleophiles, diethylphosphite, diphenylphosphonite and azide ions, but they react with arsenide and selenide ions. The photostimulated reaction of neopentyl bromide with diphenylarsenide ions gave only the straightforward substitution product neopentyldiphenylarsine. On the other hand, the photostimulated reaction of bromobenzene with dineopentyl arsenide ions gave three arsines: dineopentylphenylarsine, neopentyldiphenylarsine and triphenylarsine. Neopentyl chloride reacts under irradiation with diphenylphosphide ions giving good yields of the substitution product.
Theoretical studies on the hydrolysis of urea in acid solution
Authors: Lee Ikchoon , Kim Chang Kon , Lee Byung Choon
Published: January 2005

Mechanisms of the hydrolysis of urea have been investigated using the MNDO and AMI methods. All geometries were fully optimized and the transition states were characterized by calculating force constants. The results showed that: (i) The unimolecular decomposition process via the direct intramolecular proton transfer is preferred to both the A1 and the bimolecular nucleophilic attack by water, in agreement with the experimental results of Shaw et al. in the low acidity medium. (ii) The diprotonated form of urea exists as an equilibrium species, which undergoes the A2 type hydrolysis more favorably than the monoprotonated form, as Moodie et al. found in the intermediate acidity medium. (iii) The A2 hydrolysis of the monoprotonated form is very similar to those of acetamide and methyl carbamate. (iv) As the number of the solvate water molecules increases, the activation barrier for the A2 process of the monoprotonated form increases while that for the unimolecular decomposition of the free base form decreases, indicating a possibility of the barrier height reversal in the bulk solvent in favor of the latter process, thus accommodating all the experimentally found trends in the urea hydrolysis. The A1 mechanisms involving six‐membered ring type intermediates can be ruled out as untenable since no such equilibrium species was obtained by both the MNDO and AM1 calculations.
Experimental determination of carbon vs. oxygen regioselectivity in reactions of gas‐phase enolate ions
Authors: Brickhouse Mark D. , Squires Robert R.
Published: January 2005

A gas‐phase experimental investigation of the competition between carbon and oxygen alkylation of a series of cyclic and acyclic enolate ions is described. Perfluoropropylene is shown to react in a characteristic way with oxyanions and carbanions to produce distinctive ionic products. The relative yields of these products formed in reactions with ambident enolate ions provides a measure of their intrinsic carbon vs. oxygen regioselectivity. The results for a series of enolates derived from aldehydes, ketones, esters, amides and related compounds show a wide range of reactivity which is a function of the nature of the central substituent. Most aldehyde and ketone enolates react mainly through oxygen, while enolates with σ‐acceptor of π‐donor type central substituents react mainly thorugh carbon. Ring‐size in cyclic ketone enolates also influences C vs. O regioselectivity, i.e. small‐ring enolates react mainly through carbon, while larger ring enolates (C7–C9) react preferentially through oxygen. The enolate reactivity patterns can be generally accounted for by the keto–enol energy differences for the parent carbonyl compounds, although some exceptions are evident. The origins of the highly variable, kinetically determined regioselectivities are discussed.
Group transfers 4. Arylselenide aniondiaryl diselenide exchange
Authors: Jacobson Barry M. , Kook Alan M. , Lewis Edward S.
Published: January 2005

Barriers for group transfers between nucleophiles have been postulated to be lowered when the transferring group can carry a considerable negative charge. Furthermore, anions readily subject to one electron oxidation appear to lead to lower barriers than do those of high oxidation potential. These suggestions are pursued here on the identity reaction ArSe− + ArSeSeAr → ArSeSeAr + ArSe−. Indeed the reaction is very fast, as shown by the appearance of only a single peak in the 77Se‐NMR in an acetonitrile solution containing both ArSeNa and ArSeSeAr. The rate constant can be only very roughly estimated at low temperatures and dilute solutions, and is likely diffusion controlled for Ar = phenyl and p‐methoxyphenyl. A stable intermediate (ArSe)3−, analogous to Br3−, is indicated, but quantitative stability could not be determined, from either the NMR or the UV spectra. Some properties of 77Se‐NMR are discussed.
Binding of pyridoxal‐5′‐phosphate and pyridoxamine‐5′‐phosphate: Electrochemical characterization
Authors: Eraso F. , Pineda T. , Blazquez M. , Garcia‐Blanco F. , Dominguez M.
Published: January 2005

The interaction between pyridoxal‐5′‐phosphate (PLP) and pyridoxamine‐5′‐phosphate (PMP) was studied by d.c. and differential pulse polarography. Two reduction waves (or two peaks) were observed. The first wave corresponds to the reduction of the adduct and the second to the reduction of free PLP. The behaviour was similar in analogous Schiff bases. The effects of pH, PMP concentration and the capillary characteristics were studied. The apparent formation constant as a function of the pH was calculated. Thermodynamic parameters were estimated at pH 7 and 0 · 1 M ionic strength. The polarographic and kinetic results show that the overall electrode process appears to be irreversible in a basic medium.
Dipole moments and electron distribution of acyl chlorides and acyl bromides
Authors: Exner Otto , Hnyk Drahomír , Všetečka Václav
Published: January 2005

Dipole moments of para‐substituted benzoyl chlorides and bromides, partly measured in benzene and partly recalculated from elderly literature, were analysed in terms of bond moments and additional contributions expressing the conjugation. Although the gross moments are similar, their decomposition yields different pictures for acyl chlorides and bromides. Only in the latter can significant electron transfer from the halogen be observed. On the other hand, conjugation with the benzene nucleus is strong in both aromatic acyl chlorides and bromides, but stronger in chlorides. There is agreement with the evidence from some other physical quantities but not from all.
Amines as leaving groups in nucleophilic aromatic substitution reactions. II. Hydrolysis of N‐(2,4,6‐trinitrophenyl)amines
Authors: De Vargas Elba B. , De Rossi Rita H.
Published: January 2005

The hydrolysis reactions of N‐(2,4,6‐trinitrophenyl)piperidine (2) and N‐(2,4,6‐trinitrophenyl)‐morpholine (3) were studied. Two kinetic processes well separated in time are observed in both reactions. The fastest process, which is reversible, leads to the formation of a species of λmax 260 and 410 nm and is attributed to the formation of a σ complex of stoichiometry 1 : 2 due to the addition of a second HO− to the σ complex of 1 : 1 stoichiometry. The slowest process leads quantitatively to picrate ion. The equilibrium constants for the formation of the σ complexes of 1:1 and 1:2 stoichiometries and the rate of formation and decomposition of the latter complex were determined. The kinetic data for the slow process lead to the conclusion that the picrate ion is formed from the attack of HO− on the two σ complexes, confirming previous findings. There are some differences in the calculated rates for 2 and 3 which may be an indication that the elimination of the amine is partially rate determining.
Micellar catalysis of organic reactions. 24. Comparison of SNAr reactions in hydroxy‐functionalized micelles and in the presence of cyclodextrins
Authors: Broxton Trevor J. , Christie John R. , Chung Roland P.‐T.
Published: January 2005

The basic hydrolysis of 2,4‐dinitrochlorobenzene (DNCB) and 2,4‐dinitrofluorobenzene (DNFB) was studied in the presence of β‐cyclodextrin (CDOH) and in the presence of hydroxy‐functionalized micelles containing either a primary hydroxy group [hexadecyl‐2‐hydroxyethyldimethylammonium bromide (CHEDAB)] or a secondary hydroxy group [headecyl‐2‐hydroxypropyldimethylammonium bromide (CHPDAB) and 2‐hydroxyhexadecyltrimethylammonium bromide (2‐OHCTAB)].

In all systems a biphasic reaction was observed. The first phase consisted of a competition between the additive (either micelle or cyclodextrin) and hydroxide ion for the aromatic substrate, and the second phase consisted of the hydrolysis of the trapped aryl micellar or cyclodextryl ether.

The percentage of trapping of the aromatic substrate by the cyclodextrin was similar to that found for reactions in the hydroxy‐functionalized micelles (CHPDAB and 2‐OHCTAB) which contained secondary hydroxy groups. The relative rates of reaction for DNFB and for DNCB, i.e. F/Cl rate ratios, in the presence of CDOH were similar to those obtained in the presence of 2‐OHCTAB but less than that obtained in the presence of CHEDAB. These results support the assumption that in CDOH the secondary hydroxy groups of C‐2 or C‐3 are involved in covalent bond formation with the aromatic substrate rather than the primary hydroxy group of C‐6. All the reactions studied proceed much more slowly in the presence of CDOH than in the presence of the hydroxy‐functionalized micelles. This may reflect a catalytic effect of the positively charged surface present in the micelles but not in the cyclodextrin.
Cation radical pericyclic reactions: Cyclopropanation
Authors: Bauld Nathan L. , Stufflebeme Gary W. , Lorenz Kurt T.
Published: January 2005

Triarylaminium salts smoothly catalyze the cyclopropanation of dienes, styrenes and tetrasubstituted alkenes by ethyl diazoacetate. The reactions are regioselective and, in the case of additions to conjugated dienes, cyclopropane‐periselective. A cation radical chain mechanism involving carbene transfer from ethyl diazoacetate to a substrate cation radical is proposed.
Self‐catalysis and molecular complexes in aromatic nucleophilic substitution reactions: Reaction between 1,3,5‐trinitrobenzene and 1,8‐diazabicyclo [5.4.0] undec‐7‐ene in toluene
Authors: Forlani Luciano , Cimarelli Cristina
Published: January 2005

The formation of a σ‐like complex by reaction between 1,3,5‐trinitrobenzene and 1,8‐diazabicyclo [5.4.0]‐undec‐7‐ene was investigated in toluene at various temperatures. The kinetic data showed autocatalytic behaviour. Inspection of the reaction mixtures at zero reaction time indicated the presence of an equilibrium preceding the attack of the nucleophile, affording a molecular complex (substrate–nucleophile) which is responsible for the observed kinetic features. The present and the previous data led to the conclusion that the catalytic behaviours usually observed in SNAr reactions (in apolar solvents with amines as nucleophiles) are better explained by the presence of substrate‐catalyst interactions than by catalysis on departure of the proton and leaving group from the zwitterionic intermediate.
Oxidation of substituted ethanols by sodium N‐bromobenzenesulphonamide: A kinetic study
Authors: Puttaswamy  , Mahadevappa D. S.
Published: January 2005

The kinetics of the oxidation of seven substituted ethanols by sodium N‐bromobenzenesulphonamide or bromamine‐B (BAB) in the presence of HCl was studied at 45 °C. The rate shows a first‐order dependence on [BAB]0 and is fractional in [alcohol]0, [H+] and [Cl−]. Ionic strength variations, addition of benzenesulphonamide reaction product and variation of dielectric constant of the medium have no effect on the rate. The solvent isotope effect k/k ≈ 0·97. The rates do not correlate satisfactorily with Taft's substituent constants. Activation parameters ΔH≠, ΔS≠, ΔG≠ and log A were calculated by studying the reaction at different temperatures (308–323 K). It was found that ΔH≠ and ΔS≠ are linearly related and an isokinetic relationship is observed with isokinetic temperature β = 393 K, indicating enthalpy as a controlling factor.
Probing of transient photoenol formation from ortho‐methyl‐substituted phenyl ketones by hydrogen–tritium exchange
Authors: Gȩbicki Jerzy , Reimschüssel Władysław , Zurawińska Beata
Published: January 2005

Studies on the photochemically induced hydrogen–tritium exchange in o‐methyl‐substituted phenyl ketones are reported. It is shown that the tritium exchange can be beneficial for probing transient photoenol formation, particularly when photochemical side‐reactions are occurring.