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1.
ACS Omega ; 5(14): 8242-8250, 2020 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-32309734

RESUMO

A novel copper-mediated carboxylation strategy of aryl- and heteroaryl-stannanes is described. The method serves as a mild (i.e., 1 atm) carboxylation method using stable carbon dioxide and is transferable as a radiosynthetic approach for carbon-11-labeled aromatic and heteroaromatic carboxylic acids using sub-stoichiometric quantities of [11C]CO2. The methodology was applied to the radiosynthesis of the retinoid X receptor agonist, [11C]bexarotene, with a decay-corrected radiochemical yield of 32 ± 5% and molar activity of 38 ± 23 GBq/µmol (n = 3).

2.
Mol Imaging ; 18: 1536012119869070, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31429375

RESUMO

Machine learning (ML) algorithms have found increasing utility in the medical imaging field and numerous applications in the analysis of digital biomarkers within positron emission tomography (PET) imaging have emerged. Interest in the use of artificial intelligence in PET imaging for the study of neurodegenerative diseases and oncology stems from the potential for such techniques to streamline decision support for physicians providing early and accurate diagnosis and allowing personalized treatment regimens. In this review, the use of ML to improve PET image acquisition and reconstruction is presented, along with an overview of its applications in the analysis of PET images for the study of Alzheimer's disease and oncology.


Assuntos
Doença de Alzheimer/diagnóstico por imagem , Aprendizado de Máquina , Imagem Molecular/métodos , Neoplasias/diagnóstico por imagem , Tomografia por Emissão de Pósitrons/métodos , Animais , Humanos
3.
Phys Chem Chem Phys ; 20(31): 20555-20570, 2018 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-30052251

RESUMO

The Lewis acid-base complexation chemistry of dimethyl- and diphenylstannylene (SnMe2 and SnPh2, respectively) in hexanes solution has been studied by laser photolysis methods. Complexation of the two stannylenes with a series of nine O-, S-, and N-donors (including cyclic and acyclic dialkyl ethers and sulfides, a primary, secondary, and tertiary amine, ethyl acetate and acetone), two alkenes, and an alkyne proceeds rapidly and reversibly to generate the corresponding stannylene-donor Lewis pairs, which have been detected in each case by time-resolved UV-vis absorption spectroscopy. The complexes exhibit UV-vis absorption maxima in the range of λmax ∼ 310-405 nm depending on the donor and substitution at tin. Bimolecular rate constants for complexation (kC), which could be determined for 14 of the 24 Lewis pairs that were studied, were found to fall within a factor of four of the diffusional limit in all cases, with SnMe2 showing consistently higher reactivity than SnPh2. Equilibrium constants for complexation (KC) could be measured for all but one of the stannylene-π- and O-donor pairs, the values corresponding to (gas phase) binding free energies in the range of +1.1 to -3.9 kcal mol-1. Comparison of the experimental equilibrium constants for complexation of SnMe2 and SnPh2 with methanol and diethyl ether to those measured previously for the homologous silylenes and germylenes indicates that Lewis acidity decreases in the order SiR2 > SnR2 > GeR2 for both the dimethyl- and diphenyltetrylene series, the diphenyl derivatives exhibiting significantly stronger Lewis acidity in all three cases. The experimental trends in the binding energies and UV-vis spectra of the complexes are reproduced well by density functional theory (DFT) calculations, which have been carried out at the (TD)ωB97XD/def2-TZVP level of theory. The experimental data also show evidence of a reaction between tetramethyldistannene (Me2Sn[double bond, length as m-dash]SnMe2, 4a) and amine donors, which is suggested to afford the corresponding amine-stabilized stannylidenestannylene structure. The mechanistic proposal is supported by DFT calculations of the complexation of 4a and SnMe2 with model O-, S- and N-donors.

4.
Dalton Trans ; 41(26): 8123-34, 2012 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-22481250

RESUMO

Functionalized diaminophenols, H(N(R1R2)N(R3)O), were investigated as ligands for indium catalysts in the ring-opening polymerization of racemic lactide. Precursor complexes (N(Me2)N(Me)O)InCl(2) (1), (N(Pr2)NO)InCl(2) (2), and (N(Mes)NO)InCl(2) (3) were synthesized and fully characterized by (1)H and (13)C NMR spectroscopy, elemental analysis, and single-crystal X-ray crystallography. Complexes 1 and 2 were used to synthesize alkoxy-bridged complexes [(N(Me2)N(Me)O)InCl](2)(µ-Cl)(µ-OEt) (4) and [(N(Pr2)NO)InCl](2)(µ-Cl)(µ-OEt) (5). These complexes catalysed the polymerization of racemic lactide at different rates, with complex 5 being substantially more active than complex 4. The dissociation behaviour of these catalysts in the presence of lactide was also studied and used to make comparisons with previously reported catalyst systems.


Assuntos
Dioxanos/química , Índio/química , Ligantes , Catálise , Complexos de Coordenação/síntese química , Complexos de Coordenação/química , Cristalografia por Raios X , Espectroscopia de Ressonância Magnética , Conformação Molecular , Polimerização , Estereoisomerismo
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