Ionic Liquids in Heterocyclic Synthesis Martins, Marcos A. P; Frizzo, Clarissa P; Moreira, Dayse N ...
Chemical reviews,
06/2008, Letnik:
108, Številka:
6
Journal Article
Recenzirano
The effects of ionic liquids in cyclocondensation reactions are examined. The improvement in yield and shortening of reaction time due to these liquids can be explained by the theory of solvent ...effects.
Solvent-Free Heterocyclic Synthesis Martins, Marcos A. P; Frizzo, Clarissa P; Moreira, Dayse N ...
Chemical reviews,
09/2009, Letnik:
109, Številka:
9
Journal Article
Recenzirano
The solvent-free synthesis of heterocyclic compounds is studied. The use of solvent-free conditions resulted in similar outcomes and reduction times compared with molecular solvents.
Titania (TiO₂)-based nanocomposites subjected to light excitation are remarkably effective in eliciting microbial death. However, the mechanism by which these materials induce microbial death and the ...effects that they have on microbes are poorly understood. Here, we assess the low dose radical-mediated TiO₂ photocatalytic action of such nanocomposites and evaluate the genome/proteome-wide expression profiles of Pseudomonas aeruginosa PAO1 cells after two minutes of intervention. The results indicate that the impact on the gene-wide flux distribution and metabolism is moderate in the analysed time span. Rather, the photocatalytic action triggers the decreased expression of a large array of genes/proteins specific for regulatory, signalling and growth functions in parallel with subsequent selective effects on ion homeostasis, coenzyme-independent respiration and cell wall structure. The present work provides the first solid foundation for the biocidal action of titania and may have an impact on the design of highly active photobiocidal nanomaterials.
We have prepared a photoresponsive metal–organic framework by using an amide-based 2rotaxane as linker and copper(II) ions as metal nodes. The interlocked linker was obtained by the hydrogen ...bond-directed approach employing a fumaramide thread as template of the macrocyclic component, this latter incorporating two carboxyl groups. Single crystal X-ray diffraction analysis of the metal–organic framework, prepared under solvothermal conditions, showed the formation of stacked 2D rhombohedral grids forming channels decorated with the interlocked alkenyl threads. A series of metal–organic frameworks differing in the E/Z olefin ratio were prepared either by the previous isomerization of the linker or by postirradiation of the reticulated materials. By dynamic solid state 2H NMR measurements, using deuterium-labeled materials, we proved that the geometry of the olefinic axis of the interlocked struts determined the obtention of materials with different independent local dynamics as a result of the strength of the intercomponent noncovalent interactions. Moreover, the usefulness of these novel copper-rotaxane materials as molecular dosing containers has also been assayed by the diffusion and photorelease of p-benzoquinone, evaluated in different solvents and temperatures.
The dethreading of a series of succinamide-based 2rotaxanes bearing benzylic amide macrocycles is reported herein. These transformations proceeded quantitatively either under flash vacuum pyrolysis, ...conventional heating, or microwave irradiation. Studying the size complementarity of the stoppers at the ends of the thread and the cavity of the macrocycle allowed us to set up the best substituents for implementing the extrusion of the thread from the interlocked precursors. A variety of 1H NMR kinetic experiments were carried out in order to evaluate the rate constants of the dethreading process, the half-life times of the rotaxanes, and the influence of temperature and solvents on these processes. The use of dibutylamino groups as stoppers yielded the rotaxane precursor in a reasonable yield and allowed the quantitative deslipping of the rotaxane. The overall process, including the rotaxane formation and its further dethreading, has been exploited for preparing benzylic amide macrocycles enhancing, in most cases, the results of the classical (2 + 2) condensation and other reported stepwise syntheses. The kinetics of the dethreading process is fairly sensitive to the electronic effects of the substituents on the isophthalamide unit or to the electronic nature of the pyridine rings through a conformational equilibrium expanding or contracting the cavity of the interlocked precursor.
Coated TiO2 nanoparticles by dicationic imidazolium-based ionic liquids (ILs) were prepared and studied by differential scanning calorimetry (DSC), dynamic light scattering (DLS), transmission ...electron microscopy (TEM), powder X-ray diffraction (XRD), and scanning electron microscopy (SEM). Three ILs with different hydrophobicity degrees and structural characteristics were used (IL-1, IL-2, and IL-3). The interaction between IL molecules and the TiO2 surface was analyzed in both solid state and in solution. The physical and chemical properties of coated nanoparticles (TiO2 + IL-1, TiO2 + IL-2, and TiO2 + IL-3) were compared to pure materials (TiO2, IL-1, IL-2, and IL-3) in order to evaluate the interaction between both components. Thermal behavior, diffraction pattern, and morphologic characteristics were evaluated in the solid state. It was observed that all mixtures (TiO2 + IL) showed different behavior from that detected for pure substances, which is an evidence of film formation. DLS experiments were conducted to determine film thickness on the TiO2 surface comparing the size (hydrodynamic radius, R h) of pure TiO2 with coated nanoparticles (TiO2 + IL). Results showed the thickness of the film increased with hydrophobicity of the IL compound. TEM images support this observation. Finally, X-ray diffraction patterns showed that, in coated samples, no structural changes in TiO2 diffraction peaks were observed, which is related to the maintenance of the crystalline structure. On the contrary, ILs showed different diffraction patterns, which confirms the hypothesis of interactions happening between IL and the TiO2 nanoparticles surface.
The selective N- or O-alkylation of 4-(trihalomethyl)pyrimidin-2(1H)-ones, using 5-bromo enones/enaminones as alkylating agents, is reported. It was found that the selectivity toward the N- or ...O-regioisomer is driven by the substituent present at the 6-position of the pyrimidine ring, thus enabling the preparation of each isomer as the sole product, in 60–95% yields. Subsequent cyclocondensation of the enaminone moiety with nitrogen dinucleophiles led to pyrimidine–azole conjugates in 55–83% yields.
The crystallization mechanisms of a series of fourteen 7-chloro-4-substituted-quinolines (substituents: (
1
) OCH
3
, (
2
) OCH
2
CH
3
, (
3
) OCH
2
CH&z.dbd;CH
2
, (
4
) O(CH
2
)
2
OH, (
5
) O(CH
2
...)
3
OH, (
6
) NH(CH
2
)
2
CH
3
, (
7
) NH(CH
2
)
3
CH
3
, (
8
) NH(CH
2
)
2
OH, (
9
) NHCH(CH
2
CH
3
)CH
2
OH, (
10
) NH(CH
2
)
2
Cl, (
11
) NHN&z.dbd;CH(C
6
H
5
), (
12
) NHN&z.dbd;CH(2-FC
6
H
4
), (
13
) NHN&z.dbd;CH(3-FC
6
H
4
), and (
14
) NHN&z.dbd;CH(4-FC
6
H
4
)) were proposed based on a retrocrystallization approach using the supramolecular cluster as demarcation. Crystallization mechanism stage parameters -
N
CG
% and NG/NC - were determined. The 4-substituents present in quinolines caused six different mechanisms, starting from the monomers in solution to dimers, 1D nuclei, and 2D nuclei (
6
,
11
,
12
); 2D nucleus formation (
5
); 1D nuclei to 2D nuclei (
7
,
9
); concomitant dimers and 1D nuclei to a 3D crystal (
8
); 1D nuclei directly to a 3D crystal lattice (
1-4
,
10
,
14
), and dimers to 2D nuclei and then to a 3D crystal (
13
). Analysis of
G
AI
showed atom atom intermolecular interactions in the proposed first nuclei for compounds
4
and
5
. The nucleation process inferred in the solid state was partially confirmed during the formation of the proto-crystal in solution due to the changes of the hydrogen chemical shift in variable-concentration
1
H-NMR experiments. Results revealed that the size of the alkyl chain and the presence of different functional groups in the 4-substituents influenced the crystallization process.
The crystallization mechanisms of a series of fourteen 7-chloro-4-substituted-quinolines were proposed based on a retrocrystallization approach using the supramolecular cluster as demarcation.
The synthetic potential of 5-bromo-1,1,1-trifluoro-4-methoxypent-3-en-2-one toward the catalyst-free synthesis of N-pyrrolyl(furanyl)-piperazines, 1,4-diazepanes, and 1,4-diazocanes through a ...telescoped protocol is reported. This three-component one-pot method provided 23 examples with high chemo- and regioselectivity at yields up to 96%.
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