- METHOD FOR PREPARING P-HYDROXYMANDELIC COMPOUNDS IN STIRRED REACTORS
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The process allows the preparation of a p-hydroxymandelic compound, comprising at least one step of condensation of at least one aromatic compound bearing at least one hydroxyl group and whose para position is free, with glyoxylic acid, the condensation reaction being performed in at least one reactor equipped with at least one mixing means, the specific mixing power being between 0.1 kW/m3 and 15 kW/m3. In addition, the invention also relates to a process for preparing a 4-hydroxyaromatic aldehyde by oxidation of this p-hydroxymandelic compound.
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- Direct oxidation of the C(sp2)-C(sp3) bond from benzyltrimethylsilanes to phenols
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A novel pathway for direct conversion of benzylsilanes to phenols by oxidation with Na2S2O8 and oxygen is efficiently developed under mild and neutral conditions. The reaction shows good functional group tolerance to afford phenols in moderate yields. The possible mechanism is proposed based on the isotopic labeling trials.
- Li, Wei,Gao, Guolin,Gao, Yuan,Yang, Chao,Xia, Wujiong
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supporting information
p. 5291 - 5293
(2017/07/10)
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- Chemoenzymatic total syntheses of ribisins A, B, and D, polyoxygenated benzofuran derivatives displaying NGF-potentiating properties
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Total syntheses of the structures, 1, 2, and 4, assigned to the biologically active natural products ribisins A, B, and D, respectively, have been achieved using the microbially derived and enantiomerically pure cis-1,2-dihydrocatechol 5 as starting material. Key steps include Suzuki-Miyaura cross-coupling, intramolecular Mitsunobu, and tandem epoxidation/rearrangement reactions. As a result of these studies, the structures of ribisins A and D have been confirmed while that of congener B was shown to be represented by 31 rather than 2.
- Lan, Ping,Banwell, Martin G.,Willis, Anthony C.
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p. 2829 - 2842
(2014/05/06)
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- Synthesis of bulky 1,2-dialkoxy- and 1,2,3-trialkoxy-arenes
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A large series of bulky 1,2-dialkoxy- and 1,2,3-trialkoxy-benzenes was efficiently prepared via Williamson etherification. Preparation of their contiguous bromine-containing derivatives was also achieved.
- Stephan, Michel,Zupancic, Borut,Mohar, Barbara
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experimental part
p. 6308 - 6315
(2011/09/19)
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- Facile and sensitive spectrophotometric determination of propoxur in formulations and environmental samples
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A facile, rapid, and sensitive spectrophotometric method for the determination of propoxur in insecticidal formulations, fortified water, vegetables, agricultural wastewater, and agricultural soil samples has been elaborated. The proposed method is based on the hydrolysis of propoxur under basic conditions, followed by instantaneous azo coupling of the resulting 2-isopropoxyphenol with the anilines 2a - c. This yielded the orange-red chromophore 3a (λmax = at 470 nm). the pale-red coupling product 3b (490 nm), or the red derivative 3c (478 nm), which are stable for 46 h, 38 h, and 24 h, respectively, and could be readily analyzed spectrophotometrically.
- Kumar, Kailasa Suresh,Suvardhan, Kanchi,Rekha, Dasari,Jayaraj,Chiranjeevi, Pattium
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p. 1022 - 1027
(2007/10/03)
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- Development of natural product-derived receptor tyrosine kinase inhibitors based on conservation of protein domain fold
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Receptor tyrosine kinases (RTKs) such as Tie-2, IGF1R, Her-2/Neu, EGFR, and VEGFR1-3 play crucial roles in the control of cell growth and differentiation. Inhibition of such RTKs has become a major focus of current anticancer drug development, and therefore the discovery of new classes of inhibitors for these signal-transducing proteins is of prime importance. We have recently proposed a novel concept for improving the hit-finding process by employing natural products as biologically validated starting points in structural space for compound library development. In this concept, natural products are regarded as evolutionary chosen ligands for protein domains which are structurally conserved yet genetically mobile. Here we report on the discovery of novel and highly selective VEGFR-2 and -3, Tie-2, and IGF1R inhibitors derived from the naturally occurring Her-2/Neu kinase inhibitor nakijiquinone C and developed on the basis of this concept. Based on the structure of the natural product, a small library (74 members) was synthesized and investigated for inhibition of kinases with highly similar ATP-binding domains. The library yielded inhibitors with IC50s in the low micromolar range with high frequency (7 out of 74). In particular, four inhibitors of Tie-2 were found, a kinase critically involved in the formation of new blood vessels from preexisting ones (angiogenesis) and believed to be a new promising target in antitumor therapy. These results support the "domain concept". To advance the development of improved inhibitors, extensive molecular modeling studies were undertaken, including the construction of new homology models for VEGFR-2 and Tie-2. These studies revealed residues in the kinase structure which are crucial to the development of tailor-made receptor tyrosine kinase inhibitors.
- Kissau, Lars,Stahl, Petra,Mazitschek, Ralph,Giannis, Athannasios,Waldmann, Herbert
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p. 2917 - 2931
(2007/10/03)
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- A fluorescence detection scheme for capillary electrophoresis of N- methylcarbamates with on-column thermal decomposition and derivatization
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This paper describes a fluorescence detection method for N- methylcarbamate (NMC) pesticides in micellar electrokinetic chromatography (MEKC) separation. Fulfillment of the fluorescence detection hinged on the discovery that quaternary ammonium surfactants (particularly cetyltrimethylammonium bromide, CTAB), besides serving as hydrophobic pseudophases in MEKC, are also capable of catalyzing the thermal decomposition of NMCs to liberate methylamine. Thus, a multifunctional MEKC medium consisting of borate buffer, CTAB, and derivatizing components (o- phthaldialdehyde/2-mercaptoethanol) was formulated, which allowed first normal MEKC separation, subsequent thermal decomposition, and finally in situ derivatization of NMCs. With careful optimization of the operation conditions, fluorescence detection of 10 NMC compounds was achieved, with column efficiencies typically higher than 50 000 and detection limits better than 0.5 ppm. The present work represents an unprecedented effort in capillary electrophoresis (CE), in which an intact capillary was consecutively utilized as chambers for separation, decomposition, derivatization, and detection, without involving any interfacing features. The success in the implementation of such a detection system resulted in strikingly simple instrumentation as compared with the traditional postcolumn fluorescence determination of NMCs by reversed-phase HPLC. Similar protocols should be workable in the determination of a wide range of pesticides and pharmaceuticals in CE formats.
- Wu, Yuan Sheng,Lee, Hian Kee,Li
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p. 1441 - 1447
(2007/10/03)
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- Cesium fluoride-mediated claisen rearrangements of phenyl propargyl ethers: Substituent effects of an orthoalkoxy group on the benzene ring or modified propargyl residues
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The expected 7-alkoxy-2-methylbenzo[b]furans were effectively given in the CsF-mediated Claisen rearrangement of phenyl propargyl ethers with an o-alkoxy substituent on the benzene ring. On the other hand CsF did not affect the production of the corresponding benzo[b]furans when ethers, carrying a propargyl residue modified by either 1,1-dimethyl or 3-ethoxycarbonyl functions, were used as substrates in the rearrangement.
- Ishikawa, Tsutomu,Mizutani, Akiko,Miwa, Chizue,Oku, Yumie,Komano, Naoko,Takami, Atsuya,Watanabe, Toshiko
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p. 2261 - 2272
(2007/10/03)
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- Process for the production of N-methylcarbamates
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Process for the production of N-methylcarbamates: STR1 (wherein RO- is the radical of a substituted phenol or of a naphthol), wherein: in a first reaction step methylamine and diphenyl carbonate are reacted with each other, operating in the liquid phase and as a continuous process, in order to form phenol and phenyl-N-methylurethane; in a second reaction step phenyl-N-methylurethane, within the related reaction mixture outcoming from the first step, is thermally continuously decomposed, to yield a gaseous stream containing methyl isocyanate, from which the components different than methyl isocyanate are condensed off; in a third step the methyl isocyanate stream, outcoming from the second step, after an optional preliminary condensation, is continuously fed and contacted with a solution of a substituted phenol or of a naphthol in an inert organic solvent, containing a basic catalyst, to form N-methylcarbamate (I); N-methylcarbamate (I) is finally recovered from the reaction mixture outcoming from the third step.
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- Preparation of monoalkyl ethers of hydroxyphenols
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A process for the preparation of a monoalkyl ether of a hydroxyphenol of the formula STR1 in which Z each independently is hydrogen or a substituent which is stable under the reaction conditions, R is lower alkyl, and n is 1, 2, 3 or 4, comprising reacting a hydroxyphenol of the formula STR2 with an alkyl halide, alkyl sulphonate or aryl sulphonate alkylating agent of the formula in which X is a halogen atom, or an alkylsulphonyloxy or arylsulphonyloxy radical, at a temperature from about 130° C. to 200° C. and in the presence of an alkali metal base or alkaline earth metal base and of a diluent comprising a polyhydroxyalkyl ether having at least one OH group. Advantageously the base is sodium carbonate, sodium bicarbonate, potassium carbonate or potassium bicarbonate, the hydroxyphenol is pyrocatechol, the alkylating agent is isopropyl chloride, isopropyl C1-4 -alkyl-1-sulphonate, isopropyl benzenesulphonate or isopropyl tolyenesulphonate, and the polyhydroxyalkyl ether is glycol monomethyl ether, about 1.5 to 1.8 mols of alkylating agent and about 1 to 2 mols of the base being employed per mol of pyrocatechol, about 1.5 to 2.5 parts by weight of the glycol monomethyl ether being employed per part by weight of pyrocatechol, the reaction being effected in an inert atmosphere under elevated pressure.
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- Reductive Cleavage of Ether and Thioether Bonds on 1,3-Benzodioxole and 1,3-Benzoxathiole Derivatives
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The reaction of lithium and sodium diethylamide with 1,3-benzodioxoles and 1,3-benzoxathioles is here reported. 1,3-Benzodioxoles exhibit selective cleavage of the ether bond with formation of alkoxyphenols; 1,3-benzoxathioles when reacting with sodium diethylamide lead to 2-alkoxybenzenethiols while with lithium diethylamide give 2-alkoxybenzenethiols together with 2-(alkylthio)phenols.
- Melis, Stefana,Piras, Pier Paolo,Plumitallo, Antonio,Sotgiu, Francesca
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p. 1413 - 1414
(2007/10/02)
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- SELECTIVE DEALKYLATIONS OF ARYL ALKYL ETHERS AND THIOETHERS BY SODIUM IN HMPA
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The reaction of sodium with bis- and tris(alkoxy)benzenes in HMPA gives selectively the products of monodealkylation.The reaction proceeds through a dianion which fragments into an alkyl and an aryloxy anion.The positional selectivity of this fragmentation is governed by the structure of both the alkyl and aryloxy groups.With bis- and tris(alkoxy)benzenes which for symmetry reasons can afford aryloxy anions having the same basicity, the dealkylation involves exlusively the less substituted alkyl group.On the contrary, in the asymmetric terms, the positional selectivity of the dealkylation process is governed by the basicity of the aryloxy anion.On the basis of these concepts several efficient and synthetically useful reactions have been developed.In most cases the selectivity obtained in the present reactions in different from that observed with other previously developed methods which use sodium methoxide or sodium alkenethiolates in HMPA.It is shown that the appropriate choice of the reagent allows selective dealkylation of the desired alkoxy group of a poly(alkoxy)benzene.The reaction of sodium with bis(alkylthio)benzenes in HMPA gives the bis(mercapto)benzenes.If the reduction is carried out with a solution of sodium in HMPA, the reaction gives instead the products of monodealkylation.This however is not selective.It is suggested that in the case of thioethers the dealkylation products originate from the fragmentation of the radical anions.
- Testaferri, L.,Tiecco, M.,Tingoli, M.,Chianelli, D.,Montanucci, M.
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p. 3687 - 3692
(2007/10/02)
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- Catalytic dehydrogenation
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A method of producing an aromatic compound comprises dehydrogenating a compound having a six-membered carbocyclic ring in the molecule, the ring having a degree of saturation greater than that of a benzene ring, the dehydrogenation being carried out in the presence of a catalyst system comprising elemental palladium together with sodium carbonate and sulphur. The compound to be dehydrogenated may be a substituted cyclohexane. When the substituted cyclohexane is an alkoxycyclohexanol, the aromatic compound produced is an alkoxy phenol. In particularly useful aspect of the invention the substituted cyclohexane is a 2-alkoxycyclohexanol, the aromatic compound produced being an ortho-alkoxy phenol.
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- Synthesis of 2-alkoxyphenols
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A reductive hydrogenolysis of a 2-substituted 1,3-benzodioxole is carried out employing a hydride-donating reducing agent system to produce a 2-alkoxyphenol.
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- Preparation and dehydrogenation of cycloalkanol derivatives
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Alkanols, alkylamines or hydroxylamines are reacted with a cycloalkene oxide in the presence of Fuller's earth as a catalyst to prepare, respectively, 2-cycloalkanol ethers, 2-alkylamino-cycloalkanols, or 2-hydroxylamino-cycloalkanols.
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