Síntese e caracterização de complexos de platina(IV) com derivados N-benzilados da 1,3-propanodiamina

The present work describes the synthesis of a series of platinum(IV) complexes with N-benzyl 1,3-propanediamine derivatives. Since substitution of the axial ligands in the platinum(IV) complexes may alter their pharmacological properties, we have prepared complexes with different groups, such as hydroxide, chloride and acetate using a sequence of substitution reactions. The resulting complexes were fully characterized by IR, ¹H, 13C and 195Pt NMR spectroscopies, and elemental analysis.

Síntese de novas amidas graxas a partir da aminólise de ésteres metílicos

Recent biochemical and pharmacological studies have led to the characterization of different fatty acid amides as a new family of biologically active lipids. Here, we describe the synthesis of new amides from C16:0, 18:0, 18:1 and 18:1, OH fatty acids (FFA) families with cyclic and acyclic amines and demonstrate for the first time that these compounds produce citotoxic effects. Application of this method to the synthesis of fatty acid amides was performed using the esters aminolysis as a key step and various carboxylic amides were prepared in good yield from fatty acid methyl esters (FAMEs).

Preparação e caracterização espectroscópica de complexos de boro: uma proposta para uma prática integrada de química inorgânica

As a proposal for an undergraduate second or third year inorganic laboratory course, the present paper describes the preparation of three representative boron complexes: potassium tetrafluoroborate, pyridoxin boron complex and potassium bis(oxalato)borate. The complexes are characterised by infrared and multinuclear magnetic resonance spectroscopy (¹H, 11B and 19F) where isotopic effects are demonstrated.

Síntese e caracterização estrutural do ligante isatina-3-(N4-benziltiossemicarbazona) e do seu complexo de mercúrio(II)

The reaction of 4-(phenyl)thiosemicarbazide with isatin yielded a new ligand, isatin-3-(N4-benzylthiosemicarbazone). Isatin-3-(N4-benzylthiosemicarbazone) deprotonated in ethanol/KOH reacts with an ethanolic solution of Hg(NO3)2 to give a mercury complex. The compounds were characterized by IR and X-ray single crystal structure determination. The X-ray studies revealed that the complex possesses a tetrahedral geometry with two deprotonated thiosemicarbazone ligands coordenated. The ligand and its mercury complex crystallize in the monoclinic (P2(1)/c) and triclinic (P-1) crystal system, respectively.

Síntese de fotoprotetores e sua imobilização em poli(metacrilato de metilo): um projeto integrado de química orgânica, química de polímeros e fotoquímica

Dibenzalacetone and other aldol condensation products are known sunscreens commonly used in cosmetics. This type of compounds can easily be prepared in an Organic Chemistry Lab by reaction of aldehydes with ketones in basic medium. These compounds can be incorporated in poly(methyl methacrylate) and used as UV light absorbers, for example in sunglasses. This project has the advantage of using inexpensive reagents which are readily available in Chemistry Laboratories. This experiment can also be a base starting point for discussions of organic, polymer and photochemistry topics.

O estado da arte da síntese de semicondutores nanocristalinos coloidais

Colloidal semiconductor nanocrystals, also known as quantum dots, have attracted great attention since they have interesting size-dependent properties due to the quantum confinement effect. These nanoparticles are highly luminescent and have potential applications in different technological areas, including biological labeling, light-emitting diodes and photovoltaic devices. The synthetic methods of semiconductor nanocrystals have progressed in the last 30 years, and several protocols were developed to synthesize monodisperse nanocrystals with good optical properties, different compositions and morphologies. This review describes the main methods used to synthesize nanocrystals in the II-VI and III-V systems, and the recent approaches in this field of research.

Síntese e avaliação da atividade antimicrobiana de furanonas halogenadas e de compostos análogos aos nostoclídeos

Considering the broad spectrum of biological activity of gamma-butyrolactone derivatives, we presented the synthesis of 3,4-dihalo-5-arylidenefuran-2(5H)-ones (17-21) and analogues (24-28) of the natural product nostoclide (7,8). Furanones 17-21 were synthesized from the condensation of aromatic aldehydes with lactones 14 and 15, that were obtained from mucobromic and mucochloric acids. Lactone 15 was converted into the intermediate 23 in 36% overall yield. Compound 23 was then transformed into the nostoclide analogues 24-28. Some of the compounds prepared showed antimicrobial activities against Escherichia coli, Staphylococcus aureus and Bacillus cereus comparable to commercial antibiotics.

Curiosidades sobre a reação aldólica utilizada como etapa chave na síntese Brasileira dos ácidos pterídicos A e B

This work describes an overview of our synthesis of pteridic acids A and B and discloses some interesting results related to the lithium enolate-mediated aldol reaction used as key step to set up the C5-C15 fragment of these natural products. This first example, as far we know, of an aldol reaction between a chiral enolate of a (Z) enone and a chiral aldehyde has driven us to a series of experiments showing the remarkable relation between enolization selectivity and reaction conditions.

Oligômeros e polímeros derivados do tiofeno: síntese e aplicações

In this review we summarize recent synthetic investigations about the preparation of oligothiophenes and polythiophenes, the most important π-conjugated organic materials for applications in electrochromic and electroluminescent devices. It is showed that many interesting and novel functionalized oligothiophenes have been synthesized by convenient coupling strategies (Heck, Kumada, Negishi, Suzuki, Stille and Ullmann) and oxidative coupling methods. Synthesis of polythiophenes are also presented and described according to chemical and electrochemical polymerization methodologies. The description of these noteworthy synthetic methods illustrates how important and promising are the interdisciplinary approaches in the obtaining of oligothiophenes and polythiophenes.

Síntese de 5-nitro-isatina e 5-cloro-isatina a partir da isonitrosoacetanilida

This article describes the preparation of 5-nitroisatin and of 5-chloroisatin from isonitrosoacetanilide in a single step, using readily available and inexpensive reagents. These reactions require around 90 minutes and may be carried out as an undergraduate experiment, providing an opportunity to discuss the electrophilic aromatic substitution mechanism, as well as spectroscopic techniques for product identification.

Síntese e avaliação preliminar da atividade antinociceptiva de novas isoxazolil-aril-hidrazonas

New 2-isoxazoline aldehydes were synthesized, in good yields, from cycloadduct of the 1,3-dipolar cycloaddition reaction between endocyclic enecarbamate and carboethoxyformonitrile oxide (CEFNO). Condensation of these 2-isoxazoline aldehydes with several phenyl-hydrazines produced new isoxazolyl-aryl-hydrazones, which showed low toxicity and excellent antinociceptive activity, when compared to dipyrone. The antinociceptive activity of isoxazolyl-aryl-hydrazones was performed using the acetic acid-induced mice abdominal constrictions test.

Síntese hidrotermal assistida por micro-ondas como metodologia sintética eficiente para obtenção da rede metalorgânica [ZN(BDC)(H2O)2]n

This work presents the optimization of the microwave-assisted hydrothermal synthesis of [Zn(BDC)(H2O)2]n . The reactions were carried out at the fixed temperature of 120 ºC for 10, 20, 30 and 40 min. Pure crystalline [Zn(BDC)(H2O)2]n was obtained in high yield (ca. 90%) with a reaction time of 10 min. The phase obtained and its purity was confirmed by Rietveld refinement, with a final value for Rwp/Rexp equal to 1.48. Increased reaction times (20, 30 and 40 min) favored the formation of unwanted by products, resulting in mixtures of several crystalline phases.

Irradiação de micro-ondas aplicada à síntese orgânica: uma história de sucesso no Brasil

This review article shows the publications in the field of microwave irradiation published by Brazilian researchers over the past 10 years. In South America, Brazil leads the publication of articles with the use of microwave irradiation possessing a large advantage in number of articles published over the others countries. The works were divided into four major areas: Catalysis, Reactions without Solvent, Heterocycles Chemistry, Natural Products and Other, and some could be classified in more than one category.

Uso da FTIR na obtenção de resinas e na síntese de peptídeos em fase sólida

Despite the increase in peptide chain aggregation, which decreases the rate of coupling reactions, the synthesis and use of very highly substituted resins still remains as a controversial point in the SPPS, due to its clear economical advantages (lesser solvent consumption and higher amount of peptide per synthesis). In order to better investigate the synthesis and the use of very highly substituted resins, the FTIR, NMR and EPR were compared. By FTIR techniques it was possible to follow all the steps of resin synthesis and the factors affecting the aggregation of the chains inside the peptidil-BHAR and MBHAR.

Síntese e caracterização de argilas organofílicas contendo diferentes teores do surfactante catiônico brometo de hexadeciltrimetilamônio

The major applications of organoclays are in adsorption of organic polluents. The objective of this work was the synthesis and characterization of organoclays using differents amounts of cationic surfactant hexadecyltrimethylammonium bromide. The clays were characterized by low angle x-ray diffraction (XRD), scanning electron microscope (SEM), infrared with Fourier tranformation (FTIR), BET surface area, elemental analysis (CHN), Foster swell and adsorption of methylene blue. The surfactant can adsorb in differents forms in the interlamelar region changed the basal spacing. The presence of the surfactant adsorbed can be favorable or not in adsorption of the methylene blue due the different interactions dye-organoclays.