- Ultrasound promoted Barbier reactions and Csp3-Csp2 Stille coupling for the synthesis of diarylmethanes and substituted benzophenones
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Here we present the preparation of a variety of diarylmethanes obtained via ultrasound Stille coupling under palladium catalysis between some substituted aryl compounds and benzyltributyltin compounds generated through sonicated Barbier reaction in a very short time reaction and excellent yield. The study reported below compares different methods to optimize the synthesis of usually unstable benzyltin derivatives and is another contribution to the investigation of Csp3-Csp2 coupling process involving benzyl-aryl reagents. Substituted carboxylated benzophenones were easily prepared in a very good yield by oxidation of some diarylmethanes.
- Ocampo, Romina A.,Koll, Liliana C.,Mandolesi, Sandra D.
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- Application of complementary mass spectrometric techniques to the identification of ketoprofen phototransformation products
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Ketoprofen (KP) is a nonsteroidal anti-inflammatory drug, which during UV irradiation rapidly transforms into benzophenone derivatives. Such transformation products may occur after topical application of KP, which is then exposed to sunlight resulting in a photo-allergic reaction. These reactions are mediated by the benzophenone moiety independently of the amount of allergen. The same reactions will also occur during wastewater or drinking water treatment albeit their effect in the aqueous environment is yet to be ascertained. In addition, only a few such transformation products have been recognised. To enable the detection and structural elucidation of the widest range of KP transformation products, this study applies complementary chromatographic and mass spectrometric techniques including gas chromatography coupled to single quadrupole or ion trap mass spectrometry and liquid chromatography hyphenated with quadrupole-time-of-flight mass spectrometry. Based on structural information gained in tandem and multiple MS experiments, and on highly accurate molecular mass measurements, chemical structures of 22 transformation products are proposed and used to construct an overall breakdown pathway. Among the identified transformation products all but two compounds retained the benzophenone moietya€"a result, which raises important issues concerning the possible toxic synergistic effects of KP and its transformation products. These findings trigger further research into water treatment technologies that would limit their entrance into environmental or drinking waters. Copyright
- Kosjek, Tina,Perko, Silva,Heath, Ester,Kralj, Bogdan,Zigon, Dusan
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experimental part
p. 391 - 401
(2011/11/12)
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- Proton transfer equilibria between m-substituted benzoic acids and the carbinol base of crystal violet in apolar aprotic solvents: A comparison between toluene-phase and aqueous-phase strengths of the acids
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A detailed study on proton transfer equilibria between twelve m-substituted benzoic acids and the carbinol base of crystal violet, the reference base, in toluene at 20°C and 28°C shows that toluene-phase strengths of the acids as compared to their aqueous-phase acidities are more than 4.5 times sensitive to the substituent's structure effects.
- Sengupta, Susanta K.,Radha Rani
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p. 1057 - 1062
(2007/10/03)
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- Chemistry and stereochemistry of benzyl-benzyl interactions in MH+ ions of dibenzyl esters upon chemical ionization and collision-induced dissociation conditions
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Isobutane chemical ionization mass spectra of dibenzyl esters of a wide variety of aliphatic, olefinic, alicyclic and aromatic dicarboxylic acids exhibit abundant m/z 181 C14H13+ ions, indicating a highly general rearrangement process involving the formation of a new bond between the two benzyl groups. An extensive collision-induced dissociation and deuterium labeling study suggested that these ions are an almost equimolar mixture of isomeric α-o-tolylbenzyl, α-p-tolylbenzyl and p-benzylbenzyl cation structures, and this composition is identical for all the diesters examined. This structural assignment of the C14H13 ions suggests a mechanistic pathway for their generation, based on the formation of the new bond between the benzyl methylene group of the protonated benzoxycarbonyl and the phenyl ring of the other ester moiety via π- (and/or ion-neutral) and α-complexes. Stereoisomeric diesters show an unusual steric effect: trans-isomers give rise to much more abundant C14H13+ ions than the cis counterparts. This behavior is explained by stabilized proton-bridged structures of the MH+ ions of the cis-isomers.
- Edelson-Averbukh,Mandelbaum
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p. 515 - 524
(2007/10/03)
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- Self-sensitized photolysis of N-(1-naphthoyl)-N-phenyl-O-(benzoyl-substituted benzoyl)hydroxylamines
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The mechanism of intramolecular triplet-triplet (T-T) energy transfer and subsequent reaction in N,O-diacylhydroxylamines was investigated using the model compounds N-( 1 -naphthoyl)-N-phenyl-O-(benzoyl-substituted benzoyl)hydroxylamines (NPB) with self-sensitization abilities. An examination of the UV absorption and phosphorescence behavior as well as of energy-minimized conformations of these relatively flexible model compounds established that T-T energy transfer from the benzophenone chromophore to the naphthoyl chromophore occurs in a nearly unit efficiency exhibiting only phosphorescence derived from the latter chromophore in both methanol-ethanol (1 : 1 v/v) and 2-chlorobutane at 77 K and is more likely to proceed by a "through-space" mechanism than by a "through-bond" mechanism. The self-sensitized photolysis of NPB with 366 nm light in methanol at room temperature was found to give the fragmentation products, N-phenyl-1-naphthalenecarboxamide (PNA), benzophenone (BP), and benzoyl-substituted benzoic acids (BBA), whereas no BBA was detected in the photolysis in 1,2-dichloroethane and acetonitrile. The finding that the reaction of NPB is efficiently quenched by trans-stilbene according to the Stern-Volmer equation in both methanol and 1,2-dichloroethane indicates that all the products come from the first excited triplet state of the naphthoyl chromophore. On the other hand, the enhanced hydrogen bonding ability of the medium resulted in an increase in the quantum yield for the formation of BBA (ΦBBA) accompanied by a decrease in ΦBA holding the magnitude of ΦBBA+ΦBA nearly constant. But neither ΦPNA nor the quantum yield for the disappearance of NPB was subject to such a hydrogen-bonding effect. This intriguing result was explained in terms of a mechanism in which the N-O bond cleavage in triplet NPB gives a vibrationally excited triplet radical pair whose relaxation is very slow compared to decarboxylation of the caged benzoyl-substituted benzoyloxyl radical in 1,2-dichloroethane. Solvation of this vibrationally hot radical pair through hydrogen bonding substantially promotes its relaxation eventually affording BBA.
- Nagakubo, Hiroshi,Kubota, Gou,Kubo, Kanji,Kaneko, Tsuyoshi,Sakurai, Tadamitsu,Inoue, Hiroyasu
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p. 2603 - 2611
(2007/10/03)
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- An Exceptionally Simple Biphasic Method for the Metal Catalysed Carbonylation of Chloroarenes
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Bis(tricyclohexylphosphine)palladium dichloride is an active catalyst for the carbonylation of chloroarenes to carboxylic acids.
- Grushin, Vladimir V.,Alper, Howard
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p. 611 - 612
(2007/10/02)
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- Photochemistry of Meta-Substituted and Para-Substituted Aromatic Polycarbonyl Compounds
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Spectroscopic (λmax and ET) and photochemical (quantum yield of benzocyclobutenol formation ΦCB and Stern-Volmer quenching constant with diene KSV) properties for meta-substituted polyketones 1b-f, 2, and 5b, pa
- Ito, Yoshikatsu,Kawatsuki, Nobuhiro,Giri, Brij Pal,Yoshida, Masahiro,Matsuura, Teruo
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p. 2893 - 2904
(2007/10/02)
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- INFLUENCE OF THE ANGULAR LINKAGE ON THE MESOMORPHIC PROPERTIES OF CHOLESTERYL ARYLBENZOATES.
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Some cholesteryl esters of arylbenzoic acids incorporating angular linkage such as -Co-, -O-, -S-, and -CH//2-, were prepared, and the transition temperatures and heats determined. The cholesteric-isotropic transition temperatures are likely to correlate with the angular correlation parameters of these carboxylic acid moieties. The mesomorphic phenomena are discussed in terms of the molecular structure and electronic effect of these linkages.
- Koden,Takenaka,Kusabayashi
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p. 137 - 150
(2007/10/02)
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- Deactivation of Triplet Phenyl Alkyl Ketones by Conjugatively Electron-Withdrawing Substituents
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Para-cyano, -carbomethoxy, and -acyl substituents decrease the triplet reactivity of valerophenone (γ-hydrogen abstraction), whereas comparable meta substituents increase reactivity.Spectroscopic results are presented which indicate that para-(-R) substituents lower ?,?* triplet energies so much more than n,?* energies that the lowest triplets become largely ?,?* in nature.Meta-(-R) substituents do not stabilize ?,?* triplets enough to invert triplet levels.Both substitution patterns support a largely 1,4-biradical structure for the lowest ?,?* triplet of acylbenzenes.Ortho substituents show the usual steric anomalies: ortho cyano enhances valerophenone triplet reactivity by stabilizing the n,?* triplet; ortho carbomethoxy deactivates valerophenone by stabilizing the ?,?* triplet but not the n,?.*
- Wagner, Peter J.,Siebert, Elizabeth J.
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p. 7329 - 7335
(2007/10/02)
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