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Crystal forms of polyethersulfones (PES) were investigated by using a model compound and a low molecular weight oligomer. These are amorphous as-synthesized, and can undergo solvent-induced crystallization under the appropriate conditions. The model compound, 4,4'-bis(p-methoxyphenoxy)diphenyl sulfone, yielded monocrystals, and its structure was solved using X-ray diffraction. Conformational disorder is present, two conformers cohabiting in 55:45 proportions. This model compound, combined to previous structural studies published in the literature, served as a basis for conformational studies of polyethersulfone. Low molecular weight polymers submitted to solvent-induced crystallization resulted in a PES crystal form different from that previously published in the literature, as shown by powder X-ray diffraction. Key words: polyethersulfone, solvent-induced crystallization, crystal structure, polymorphism, X-ray diffraction. On a etudie les formes cristallines de sulfones de polyethers (SPE) en se basant sur un compose modele et un oligomere de faible poids moleculaire. Ces sont des produits amorphes obtenus par une synthese-as et, dans des conditions appropriees, ils peuvent donner lieu a une cristallisation induite par un solvant. Le compose modele, le sulfone de 4,4'-bis(p-methoxyphenoxy)diphenyle, peut etre isole sous la forme de monocristaux et on a determine sa structure par diffraction des rayons-X. On a decele un desordre conformationnel alors que deux conformeres coexistent dans des proportions de 55 : 45. Les donnees relatives au compose modele combinees aux etudes publiees anterieurement sur les structures ont servi de base pour les etudes conformationnelles des sulfones de polyethers. Les polymeres de faibles poids moleculaires soumis a une cristallisation induite par un solvant ont conduit a la formation de SPE dont la forme cristalline, d'apres la diffraction des rayons-X, serait differente de celles rapportees anterieurement dans la litterature. Mots-cles : sulfone de polyether, cristallisation induite par un solvant, structure cristalline, polymorphie, diffraction des rayons X. [Traduit par la Redaction], Introduction Polyethersulfones, abbreviated PES, stand out among other high-performance thermoplastic polymers because of their thermal stability, amorphous morphology, and good solubility in low polarity solvents (ketones and chlorinated aromatic hydrocarbons). [...]

Recent laboratory studies have demonstrated that isoprene oxidation products can partition to atmospheric aerosols by reacting with condensed phase sulfuric acid, forming low-volatility organosulfate compounds. We have identified organosulfate compounds in free tropospheric aerosols by single particle mass spectrometry during several airborne field campaigns. One of these organosulfates is identified as the sulfate ester of IEPOX, a second generation oxidation product of isoprene. The patterns of IEPOX sulfate ester in ambient data generally followed the aerosol acidity and N[O.sub.x] dependence established by laboratory studies. Detection of the IEPOX sulfate ester was most sensitive using reduced ionization laser power, when it was observed in up to 80% of particles in the tropical free troposphere. Based on laboratory mass calibrations, IEPOX added >0.4% to tropospheric aerosol mass in the remote tropics and up to 20% in regions downwind of isoprene sources. In the southeastern United States, when acidic aerosol was exposed to fresh isoprene emissions, accumulation of IEPOX increased aerosol mass by up to 3%. The IEPOX sulfate ester is therefore one of the most abundant single organic compounds measured in atmospheric aerosol. Our data show that acidity-dependent IEPOX uptake is a mechanism by which anthropogenic S[O.sub.2] and marine dimethyl sulfide emissions generate secondary biogenic aerosol mass throughout the troposphere. acid-catalyzed particle phase reactions | epoxides | free troposphere | secondary organic aerosol doi: 10.1073/pnas.1012561107

Diels-Alder reactions of 4-alkenylthiazoles were carried out to find a new approach to thaizole functionalization. Diels-Alder reactions included reactions of N-substituted maleimides, maleic anhydride and napthoquinone with high levels of stereocontrol to give the corresponding endo-cycloadducts.

Asymmetric synthesis of ring functionalized trans-2,6-disubstituted piperidines from N-sulfinyl [delta]-amino [beta]-keto phosphonates was carried out. The method involves the one-pot conversion of sulfinimine-derived N-sulfinyl [delta]-amino [beta]-ketophosphonates, the stereoselective addition of organocuprates and one the one-pot dephosphorylation of the 3-phosphoryl piperidiens.

A series of sulfonated poly(p-phenylene terephthalamide) (PPTA) polymers are prepared in three molecular configurations. The variation in the polymer alignment is due to the result of the differences in the solution properties and the film forming process.

A review of the efforts made since 1975 to understand the chemistry of a select group of sulfur-nitrogen compounds including sulfinimines and N-sulfonyloxaziridines is presented. It is observed that the exploration of sulfenamides led to the discovery of sulfenimines and sulfinimines and, ultimatley, to the invention of N-sulfonyloxaziridines and enantiopure sulfinimines.

The femtosecond pump-probe transient absorption spectroscopy is used to measure the ultrafast time-resolved electronic spectra of primary events induced in copper tetrasulfonated phthalocyanine Cu[(tsPc).sup.4-]) in aqueous solution. Combining of spectroscopy and electrochemical measurements gives clear interpretation of primary events upon light excitation, photochemical mechanisms and spectral features relating to photophysical and photochemical mechanisms.

An iodocyclization of sulfinimine-derived enantiopure homoallylic sulfonamides that represents a valuable new route for the asymmetric synthesis of trans-2,5-disubstituted pyrrolidines is described. The homoallylic sulfonamides were prepared from readily available sulfinimine-derived beta-amino aldehydes using the Wittig reaction and were obtained as E:Z mixtures.

Enantiopure aromatic (phenyl, naphthyl) and heteroaromatic (pyridyl, quinolyl, diazinyl) sulfoxides are synthesized by reaction of (S)-tert-butyl tert-butanethiosulfinate with aryl- or heteroaryllithium derivatives. An application of an enantiopure aminosulfoxide as N,S ligand for the asymmetric catalysis of allylic nucleophilic substitution is successfully tested.

Seven model substrates were synthesized and cyclized to examine the structural features responsible for imparting diastereoselection in the second intramolecular Heck reaction. The study demonstrate that stereoselection in the formation of the second spirooxindole ring results from the avoidance of steric interactions in the insertion step with the spirooxindole formed in the first Heck cyclization.

The regiospecificity of the 1,4-addition of the reported novel alkoxy chlorodisulfides to 2-methyl-1,3-butadiene is established. Periodate oxidation at room temperature, preferably in the presence of I(sub 2), resulted in oxidative cleavage and cyclization to beta-iodo alpha-beta-unsaturated gama-sultines that were also conveniently prepared by reaction of iodine with alkyl allenesulfinates.

A facile and efficient synthetic route toward highly substituted 2,3-dihydrothiopyran-4-ones was developed through a formal [5C + 1S] annulation of readily available alpha-alkenoyl ketene-(S,S)-acetals with sodium sulfide nonahydrated salt (Na(sub 2)S.9H(sub 2)O) and utilized in the synthesis of 2-(4-chlorophenyl)-6-(morpholin-4-yl)-4H-thiopyran-4-one, an inhibitor of DNA-dependent protein kinase (DNA-PK).

The assimilation and transformation of phytoplankton-derived organic sulfur compound dimethylsulfoniopropionate (DMSP) by bacteria during the microcosm experiment and relation between the changes in DMSP processing and the changes in the composition of the bacterial assemblage during the induced bloom compared to nonbloom conditions are investigated. The results show that the composition of the bacterial assemblage and the contribution of DMSP to the overall dissolved organic sulfur/organic matter pool control how efficiently bacteria assimilate DMSP S and thereby potentially divert it from DMS production.

The structure and energetics of the simplest vic-disulfoxide CH3S(O)S(O)CH3 and its key isomers are reported. The B3LYP structure obtained for 5,5-di-t-butyltetrathiolane-2, 3-dioxide reproduces the essential structural parameters of the known vic-disulfinyl compound, 5-(1-adamantyl)-5-tert-butyltetrathiolane-2,3-dioxide.

It has been demonstrated that the D parameter of the tetraradicals and hexaradicals is mainly determined by the spin density of the localized 1,3-cyclopentanediyl spin carrier. Thus the trimethylenebenzene ferromagnetic coupler is essentially negligible.

Bis(dialkylamide)hydrogen dibromobromate is used as a source of BrO(super -), and is shown that rates of dephosphorylation are similar with BrO(super -) generated from these complexes or from Br2-H2O. Reactions of 4-nitrophenyl tosylate, with BrO(super -) are rapid with 0.1 M BrO(super -), under conditions in which oxidations of organic sulfides are too fast to be followed by conventional methods.

Solvent-free synthesis of a series of alkylthio-substituted titanyl phthalocyanine (TiOPc) derivatives starting from the corresponding phthalonitriles (Pn) is reported. The process eliminated the formation of the unmetalated phthalocyanine ([H.sub.2]Pc), a side product that makes purification difficult and the alkylthio groups in the obtained derivatives enhance solubility in common organic solvents and shift the absorption to the near-IR region.

Cysteamine has reduced selenocystamine to form hemiselenocystamine and then cystamine and their rate constants are similar for reactions of cysteine/selenocystine. The reaction rates of selenium as a nucleophile and as an electrophile are 2-3 and 4 orders magnitude higher than those of sulfur.

The reanalysis of the kinetics and molecularity of the Newman-Kwart rearrangement of N,N-dimethyl O-(p-nitrophenyl)thiocarbamate in N,N-dimethylacetamide solvent is described. The studies have shown that under the microwave heating conditions, a delayed negative feedback signal to the microwave power balancing loop has resulted in oscillatory reaction overheating and due to higher tan [delta] in the solute the amplitude of the oscillation has increased with the concentration of N,N-dimethyl O-(p-nitrophenyl)thiocarbamate.

A general and efficient method is described for preparing 2,4-di- and trisubstituted thiazoles through p-TsOH.[H.sub.2]O-catalyzed cyclization of trisubstituted propargylic alcohols with thioamides. The reaction is achieved in under mild conditions that has not required the exclusion of air and moisture and has provided a convenient route to the synthetically useful aromatic heterocycle.

A general and robust racemization-free protocol is described for preparing a variety of N-tert-butanesulfinyl ketimines. The reaction progress is monitored by [super 1]H NMR by using the nonperturbing internal standard diglyme and ketimines are formed in either THF or CPME (cyclopentyl methyl ether) as solvent with heating to reflux.

Consecutive ring-expansion reactions of oxiranes with dimethylsulfoxonium methylide are analyzed and modeled at the density functional theory (DFT) and second-order Moller-Plesset (MP2) levels of theory by using a polarizable continuum model (PCM) to account for solvent effects. The studies have shown the complete conversion of the enantiomeric purities for the nucleophilic ring expansions of enantiomeric 2-mono- and 2,2-disubstituted epoxides and oxetanes with dimethylsulfoxonium methylide.

The examination of the pH-dependent mutarotation of 1-thioaldopyranoses in aqueous media is presented. 1-Thio-D-mannopyranose and 1-thio-D-altropyranose has displayed very strong pH dependence where the anomeric equilibrium ratios have changed from a preference for the [beta]-anomer at lower pH to the [alpha]-anomer at higher pH.

The synthesis, structure, redox and photophysical properties of the two- and three-layered donor-acceptor (D-A) type [3.3]paracyclophanes ([3.3]PCPs) are presented. The (p-ethylbenzenesulfonyl)methyl isocyanide coupling method is used for achieving the synthesis of the two- and three-layered [3.3]PCPs containing 2,1,3-benzothiadiazole (BTD) as an acceptor.

Silver(I) activation of thioacetoacetates in the presence of ketones has produced 1,3-dioxin-4-ones. The mechanistic studies addressing the intermediacy of an acylketene intermediate are presented.

Novel N-(Cbz-aminoacyl)thiosemicarbazides are cyclized by treatment with sulfuric acid to produce 1,3,4-thiadiazoles. These compounds have reacted with N-(Cbz-aminoacyl)- and - dipeptidoylbenzotriazoles to produce chirally pure 1,3,4-thiadiazol-2-yl-substituted amino acids and dipeptides.

Nine [beta]-hydroxy-[alpha]-sulfenyl[gamma]-butyrolactones having different substituents are prepared and crystal structures of syn-syn lactones are determined. The X-ray and theoretical studies have shown that two concomitant, attractive 1,4-intramolecular interactions of divalent sulfur with both carbonyl and hydroxyl oxygens are the driving force for the stereochemical preference and the nonbonded sulfur-oxygen interactions have controlled the stereoselectivity of the reaction.

B3LYP calculations are used for studying the reaction mechanism of the aminolysis of Fischer carbene complexes of the type [(CO).sub.5]Cr[double bond]C(XMe)R (X = O and S, R = Me and Ph). The results have shown that the transition state of the nucleophilic attack is more advanced and has a higher barrier for alkoxycarbene than thiocarbene complexes because of the stronger [pi]-donor character of the alkoxy group that has reduced the electrophilicity of the attacked carbene atom making the nucleophilic attack more difficult.

Benzopolysulfanes are prepared with a PEG group attached through an amide bond and is examine for water solubility antitumor activity and propensity to equilibrate and desulfurate. The studies have shown that solubilization of the polysulfur linkage is the main parameter for the success of these compounds ass drug leads.

Aziridinemethanol sulfonate esters have reacted with tetrathiomolybdate to produce thiirane derivatives as the major product and cyclic disulfides as minor product under mild reaction conditions via an unprecedented thia-aza-Payne-type rearrangement. It is shown that when the reaction of tetrathiomolybdate is carried out with 2-aziridino-cyclohexanol derivatives it has resulted in the formation of thia-bicyclo[3.1.1]heptane or dithia-bicyclo[3.2.1]octane derivatives.

The enantioselective total synthesis of (+)-hexachlorosulfolipid, a cytotoxin isolated from the Adriatic mussel Mytilus galloprovincialis, is presented. The total synthesis has allowed the conformation of the absolute configuration of the natural cytotoxic (+)-hexachlorosulfolipid.

Ureas and thioureas derived from L- or D-valine have acted as bifunctional organocatalysts able to induce the enantioselective alcoholysis of mono-, bi- and tricyclic meso anhydrides. Both enantiomers of the hemiesters are obtained by changing the configuration of the catalyst.

The synthesis and characterization of two new boron-based conjugated compounds containing one and three monopyrrolo-annelated tetrathiafulvalene (TTF) units. The absorption spectral and electrochemical responsiveness of these compounds toward fluoride ion is because of the binding of the boron units with fluoride ion.

Cyclic cis-[beta]-amino Weinreb amides are prepared by ring-closing metathesis of sulfinimine-derived N-sulfinyl [beta]-amino diene Weinreb amides. The unsaturated cyclic cis-[beta]-amino Weinreb amides are useful for the asymmetric synthesis of cyclic-[beta]-amino acid derivatives.

4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene bridged bis(permerthyl-[beta]-cyclodextrins) is prepared through click chemistry and it has formed a well-defined linear assembly with 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin via extremely strong host-guest interactions. The fluorescence resonance energy transfer from host spacer to porphyrin guest is examined, which has shown that the energy transfer quantum yield is high to 94% in virtue of such a noncovalent path.

The reactivity of Fenitrothion toward several O- and N-based nucleophiles, including ambident and [alpha]-nucleophiles, is examined in basic media in water containing 1,4-dioxane. A major [alpha]-effect is observed with HO[O.sup.-], N[H.sub.2]OH, and N[H.sub.2][O.sup.-], thus confirming the participation of the nucleophile in the rate-limiting step of the reaction.

Carbanions of aryl 3-chloropropylsulfoxides have reacted with nonenolizable aldehydes to provide 2,3-disubstituted tetrahydrofurans. The diastereoselectivity is attributed to the cyclic transition state of the aldol addition and has increased when the aromatic ring of the sulfoxide contains electron-withdrawing subsituents, whereas that of the aldehyde has electron-donating groups.

High-level DFT calculations, coupled with appropriate isodesmic reactions are applied to study the the effects of monoheteroatom substitution, cyclization, and unsaturation on the stability, multiplicity, and reactivity of amino-, oxy-, silyl-, phosphino-, and thioalkylcarbenes. The detailed study offer insight into the reactivity and chemistry of the developed carbenes in terms of of nucleophilicity, electrophilicity, and proton affinity.