Nelson Luís C. Domingues

A novel and efficient methodology for thio-Michael addition in the synthesis of cis-β-thio-α-aminoacid derivatives using Zn[(L)-Pro]2 as heterogeneous catalyst

A simple, efficient and green chemical ultrasound assisted thio-Michael addition reaction between thiols and (Z)-azlactones aiming to produce non-natural amino acid derivatives by using chiral Zn[(L)-Pro]2 as a heterogeneous catalyst is herein described. The product was obtained in good to excellent yields presenting high diastereoselectivity.

A new, efficient and recyclable [Ce(L-Pro)]2(Oxa) heterogeneous catalyst used in the Kabachnik–Fields reaction

Herein we introduce a new catalyst for the Kabachnik–Fields reaction, [Ce(L-Pro)]2(Oxa), using a very accessible, simple and efficient methodology for α-aminophosphonate synthesis using an aromatic aldehyde, an aromatic amine and diphenyl phosphite. This procedure was developed using a low catalyst loading of cerium(III) prolinate and it has allowed for the recycling of the catalyst.

β-Cyclodextrin as a recyclable catalyst: aqueous phase one-pot four-component synthesis of polyfunctionalized pyrroles

An elegant, mild and straightforward methodology was explored for the first time towards the synthesis of polyfunctionalized pyrroles using β-cyclodextrin as a reusable supramolecular catalyst in aqueous medium. The present method provides various diversely substituted pyrroles from the commercially available synthons in good to excellent yields. The advantages of this novel protocol are use of environmentally benign reaction medium and recyclability of β-cyclodextrin over the existing methods.

[Ce(L-Pro)2]2 (Oxa) as a heterogeneous recyclable catalyst: synthesis of pyrazoles under mild reaction conditions

We developed a novel and highly efficient protocol for the synthesis of important pyrazole derivatives by using some 1,3-dicarbonyl compounds and phenyl hydrazines via a one-pot protocol. As a recyclable heterogeneous catalyst, we used [Ce(L-Pro)2]2 (Oxa). In addition, the catalyst is recyclable, the proline is economically viable and readily available in both enantiomeric forms and the catalyst is insoluble in almost all solvents and may be easily filtered off from the reaction medium. Moreover, this new synthetic protocol features high conversion, short reaction times, a straightforward procedure and cleaner reaction profiles.

Synthesis of α-aminophosphonates using a mesoporous silica catalyst produced from sugarcane bagasse ash

A new green synthesis route is proposed for obtaining a mesoporous material using sugarcane bagasse ash (SCBA) as the silica source. The material obtained was denoted by SBA-16 and its mesostructure was characterized by low-angle X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption techniques. Sulfonic acid groups were introduced to the as-synthesized material, resulting in an acid catalyst denoted by SBA-16/SO3H. The catalytic activities of SBA-16 and SBA-16/SO3H were investigated in Kabachnik–Fields reactions, where α-aminophosphonate compounds were produced. The results show that both products can be considered as promising catalysts, where SBA-16/SO3H showed a slightly better performance than SBA-16.

Lipase catalyzed 1,2-addition of thiols to imines under mild conditions

This is the first report of enzymes used as biocatalysts for a 1,2-sulfur addition. In this study, we describe the synthesis of N,S-acetals using an environmentally friendly process with low catalyst loading and in short reaction times using porcine pancreatic lipase, chymosin, and bovine serum albumin (BSA). The hydrogen bond between the enzyme and the N-Boc imine is a key factor in this reaction.

Effect of Different Dopants in Films TEOS/MPTS Used to Protect the Carbon Steel

Schiff bases m-toluene N-Salicylideneaniline (m-TOL), (B) m-nitro-N- Salicylideneaniline (m-NTR) and (C) m-methoxy-N-salicylideneaniline (m-MTX) and cerium ions were studied added to 3.5 wt.% NaCl solution and added to the hybrid film based tetraethoxysilane (TEOS) e 3-methacryloxypropyltrimethoxysilane (MPTS). The polarization measurements showed lower current densities for the steel in NaCl with m-MTX, indicating that the m-MTX may be acting as an inhibitor. The hybrid films were doped with the m-MTX, Ce (III) or Ce (IV). Electrochemical measurements of open circuit potential (EOC), polarization curves and electrochemical impedance spectroscopy (EIS), were used to evaluate the corrosion behavior of the hybrid films. According Electrochemical Impedance measurements, all hybrid films, provided protection to the carbon steel. The films doped with Ce (IV), provided greater protection than the other, which indicates that this is the most suitable dopant for use in films.

Synthesis and characterization of the polyaniline dopant Schiff base

The Schiff base, N-salicilidenoanilina was used as dopant to induce polymerization of aniline and thus preparing polyaniline (PAni). The different conditions of preparation, including Schiff base structure, and the dosage of acidity reaction medium, were investigated to discuss the influence of these conditions relative conductivity of the resulting samples. The products were also characterized by Fourier transform infrared (FTIR), ultraviolet-visible (UV-Vis), electrochemical impedance spectroscopy (EIE). The results showed the synthesis conditions play an important in the formation and the final properties of the polyaniline

Synthesis of some derivatives of compounds β-aminoketonic through Mannich reaction by usingbiocatalysts

The Mannich reaction is one of the most widely used reactions in organic chemistry, and also one of the first examples of a multicomponent reaction already described on the literature. This reaction results in β-aminocarbonylated compounds which allow the generation of several structures that can be used in the synthesis of both biologically active molecules, and natural products, however, just a few synthetic routes resulting in the formation of β-aminocarbonylated compound are known. In this sense, new methodologies have been developed by involving new catalysts or chiral auxiliaries in the synthesis of β-aminocarbonylated compounds with biological activity. One of these methodologies is the biocatalysis, which is a technique that uses biological catalysts, like enzymes or micro-organisms to convert a substrate in a limited number of enzymatic steps. The use of micro-organisms, plants or isolated enzymes as chiral catalysts has proportioned a significant advance in the synthetic chemistry, because it is known that the biocatalysts have selective catalytic sites that afford the formation of enantiomerically pure products and which is extremely important, because it is known that differences of the chirality may have tragic or spectacular effects in humans. Concerning to the environmental issue, the biocatalysis is placed within the context of a new philosophy called Green Chemistry. However, in the State of Mato Grosso do Sul the researches involving this issue of biocatalysis are still incipient once that by the year of 2010 there was only one research group focused on this theme registered in the Lattes Platform in the State. Because of the need of support to the researches focused on this issue in the State of Mato Grosso do Sul and to evaluate the biocatalytic potential of different lineage of microorganisms and enzymes in the synthesis of compounds β-aminoketonic through Mannich reaction it was proposed the use of some enzymes such as: lipase, Lipozyme® and chymosin. The reactions were kept under stirring at room temperature from 24 to 48 hours in those which the enzymes were used like catalysts. All the reactions were monitored by thin layer chromatography. The crude of the reaction was purified on a silica gel column (70-230 mesh) and the obtained compounds were characterized by infrared spectroscopy, gas chromatography and nuclear magnetic resonance. All the reactions biocatalyzed by enzymes showed biocatalytic potential, but their concentration, the basicity of the amine and the reaction medium interfered in the reaction yield. The both three enzymes presented a higher affinity as for the less polar solvents (THF) as for the higher polar solvents (DMSO). However it was proposed the introduction of new low cost biocatalysts and environmentally safe on Mannich reactions.

Biosynthesis of some Mannich bases

The Mannich reaction is extremely useful to form molecules that contain nitrogen groups. Currently, there is a great interest turned to this class of compounds due to its biological properties. The recent literature reports that the utilization of enzymes can be an adequate methodology on this type of reaction. According to the exposed above and with the intention of synthesizing the -aminoketones, some catalysts like Chymosin and also some microorganisms such as Saccharomyces cerevisiae, (sourdough bread) and Lactobacilos (ATCC 90827LA10N19.10-E.U.A) were applied. These reactions were carried out by using water as solvent at room temperature excelling for the Green Chemistry principles. Figure 1 shows the reaction scheme involving 1 eq.mol of aniline, 1,3 eq.mol of formaldehyde, 10 ml of water and 0,25g of the catalyst during four days. The reaction furnished satisfactory yields which are in accordance with the literature data.