Search results for "SELE"
showing 10 items of 4721 documents
ChemInform Abstract: Palladium-Catalyzed Suzuki Carbonylative Reaction of α-Halomethyl Oxime Ethers: A Regioselective Route to Unsymmetrical 1,3-Oxyi…
2015
Scandium-catalyzed preparation of cytotoxic 3-functionalized quinolin-2-ones: Regioselective ring enlargement of isatins or imino isatins
2012
Trimethylsilyldiazomethane in the presence of catalytic amounts of Sc(OTf) 3 smoothly promotes the ring expansion of isatins or imino isatins to efficiently afford 3-functionalized quinolin-2-ones through controlled ring enlargement. Whereas the ring-expansion reaction of azetidine-2,3-diones led to the adduct resulting from migration of the carbonyl group, the ring-expansion reaction of oxindole derivatives gave the adduct resulting from migration of the aryl group. To rationalize the experimental observations, theoretical studies have been performed. Moreover, the biological activity of some of the synthesized heterocycles has been evaluated in four cancer cell lines. © 2012 Wiley-VCH Ver…
ChemInform Abstract: Organocatalytic Enantioselective Alkylation of Pyrazol-3-ones with Isatin-Derived Ketimines: Stereocontrolled Construction of Vi…
2016
Financial support from the MINECO (Gobierno de Espana and FEDER (EU)) (CTQ2013-47949-P) and from Generalitat Valenciana (ISIC2012/001) is gratefully acknowledged. C. V. thanks MINECO for JdC contract. Access to NMR, MS and X-ray facilities from the Servei central de support a la investigacio experimental (SCSIE)-UV is also acknowledged.
Stereoselective Synthesis of Enantiomerically Pure Piperidine Derivatives byN-Galactosylation of Pyridones
2004
Stereoselective desymmetrization of 4-pyridone has been achieved through selective N-galactosylation, activation of the N-(galactosyl)pyridone by O-silylation and immediate addition of Grignard compounds. Chiral piperidine derivatives, e.g. (S)-(+)-coniine and (5S,9S)-(+)-indolozidine 167B, were synthesised in enantiomerically pure form using these highly regio- and stereoselective reactions. After N-galactosylation of 2-pyridone and O-silylation of the N-galactosyl-2-pyridone, addition of a Grignard compound proceeded with high 1,4-regioselectivity and complete diastereoselectivity, to furnish 4-substituted 5,6-dehydro-2-piperidones. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Ger…
Leaving Group and Regioselectivity Switches in the Aminoalkylation Reaction of Indoles and Related Heterocycles with α-Amido Sulfones
2013
The regioselective aminoalkylation of indoles and related heterocycles with α-amido sulfones under basic conditions has been studied. The reaction that employed the MeMgBr/MgBr2 system provided high yields of 3-(1-carbamoylalkyl)indoles. On the other hand, the reaction that used Cs2CO3 afforded 1-(1-carbamoylalkyl)indoles exclusively in high yields. The first reaction constitutes a switch of the leaving group of the α-amido sulfone in comparison to previously reported reactions between indoles and α-amido sulfones, which provided 3-(1-arylsulfonylalkyl)indoles. The second reaction constitutes a switch in the regioselectivity. The extensions of these C- and N-aminoalkylations starting from p…
Anion Receptors Based on a Quinoline Backbone
2007
2-Amido-8-urea substituted quinoline derivatives are potent receptors for the binding of halide or benzoate anions in chloroform. The selectivity and affinity of the receptors for fluoride can be tuned by variation of the substituents at the receptor side chains. Computational considerations show that the cleft of the receptors provides space for effective binding of F–, but not bigger anions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Determination of aminoglycoside and macrolide antibiotics in meat by pressurized liquid extraction and LC-ESI-MS
2010
A simple method for the simultaneous determination of dihydrostreptomycin, spectinomycin, spiramycin, streptomycin, tilmicosin, and tylosin in meat has been developed using pressurized liquid extraction and LC-triple quadrupole MS (LC-ESI-MS/MS). The pressurized liquid extraction operational parameters were optimized and no protein precipitating and fat removing steps were required. A gradient HPLC separation was developed with ion-pair mobile phases consisting of aqueous 1 mM heptafluorobutyric acid water and methanol. Protonated molecules were used as precursor ions for CID. Data acquisition under MS/MS was achieved by applying multiple reaction monitoring of three fragment ion transition…
1992
Phosphonomethyl-substituted phenols are readily obtained from o-hydroxymethylated phenols and trialkyl phosphites. The free acids, incorporated into phenol-formaldehyde resins, act as cation exchangers with remarkable selectivity for different metal ions.
Enantioselective organocatalytic intramolecular aza-Michael reaction: a concise synthesis of (+)-sedamine., (+)-allosedamine, and (+)-coniine
2007
The intramolecular aza-Michael reaction of carbamates bearing remote alpha,beta-unsaturated aldehydes under organocatalytic conditions took place with good yields and excellent ee's when Jorgensen catalyst IV was used in the process, giving rise to the enantioselective formation of several five- and six-membered heterocycles. The developed methodology was applied to the synthesis of three piperidine alkaloids.