Filipe Penteado

Synthesis of bis(indolyl)methanes using ammonium niobium oxalate (ANO) as an efficient and recyclable catalyst

A green and efficient procedure was developed for the synthesis of bis(indolyl)methanes using ammonium niobium oxalate (ANO) NH4[NbO(C2O4)2(H2O)x]·nH2O as the catalyst and water or glycerol as the solvent. Products were obtained in good to excellent yields under conventional heating (water, 50 °C) or under sonication (glycerol, 110 °C). In the reaction in water, the catalyst was easily reused for further reactions without loss of activity.

Metal and base-free synthesis of arylselanyl anilines using glycerol as a solvent

We describe here a metal and base-free straightforward method to access arylselanyl anilines using glycerol as a solvent. Starting from N,N-disubstituted anilines and arylselanyl chloride, the protocol is general and was successfully applied to a sort of anilines with different substitution patterns in both the aromatic ring and the nitrogen atom. As desirable for a green synthetic procedure, the non-toxic, low volatile, renewable glycerol was used as a solvent at room temperature.

Antioxidant and antidepressant-like activities of semi-synthetic α-phenylseleno citronellal

In this study, the antioxidant and antidepressant-like activities of the semi-synthetic compound α-phenylseleno citronellal (PhSeCIT) and the natural terpenoid R-citronellal (CIT) were evaluated. The biological potential of PhSeCIT and CIT was evaluated by antioxidant in vitro assays, such as 1,1-diphenyl-2-picryl-hydrazyl (DPPH), 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS), ferric ion reducing antioxidant power (FRAP) and linoleic acid oxidation. The compounds were also assessed by ex vivo tests to determine the acute toxicity, levels of thiobarbituric acid reactive species (TBARS), δ-aminolevulinate dehydratase (δ-Ala-D) and Na(+)/K(+) ATPase activities. The antidepressant-like activity of compounds in the tail suspension test (TST) and forced swimming test (FST) was also investigated. The results demonstrated that the addition of an organoselenium group to (R)-citronellal increased its antioxidant properties, since PhSeCIT showed better activity than CIT. The treatment of mice with both compounds did not cause death of any animals. The levels of TBARS were significantly reduced by PhSeCIT in liver and cortex of animals, whereas CIT did not alter these parameters. In the TST and FST, PhSeCIT showed promising antidepressant-like activity, while CIT was not active in this test. Taken together, these data demonstrate the role of selenium in the antioxidant and antidepressant-like activities of (R)-citronellal.

Niobium-promoted reaction of α-phenylglyoxylic acid with ortho-functionalized anilines: synthesis of 2-arylbenzothiazoles and 3-aryl-2H-benzo[b][1,4]benzoxazin-2-ones

A new and general method to prepare 2-arylbenzothiazoles and 3-aryl-2H-benzo[b][1,4]benzoxazin-2-ones by the reaction of α-arylglyoxylic acid with o-aminothiophenol and o-aminophenol respectively is described. The use of ammonium niobium oxalate (ANO) as the catalyst and PEG-400 as the solvent were crucial to afford the title compounds in good yields and selectivity. The reaction time can be reduced from hours to few minutes when ultrasound is used as an alternative energy source.

Ultrasound-enhanced Ag-catalyzed decarboxylative coupling between α-keto acids and disulfides for the synthesis of thioesters

Herein, we described the ultrasound-assisted synthesis of thioesters via the Ag-catalyzed radical oxidative decarboxylation of α-keto acids, in the presence of disulfides. This protocol takes advantage of the sonication to prepare the title compounds in moderate to very good yields, in only 20 min of reaction. The positive effect of ultrasonic irradiation is attributed to both, the high mass transfer efficiency and to the induced radical formation in the reaction medium.

Selenium dioxide-promoted selective synthesis of mono- and bis-sulfenylindoles

A selective method for the preparation of mono- and bis-sulfenylindoles was developed using an oxidizing agent and the I2/SeO2 system as an efficient catalyst. The selectivity was controlled by varying the amount of SeO2. This represents the first example of the application of SeO2 in this type of selective chemistry.

Glicerol como Solvente em Síntese Orgânica

O glicerol e o principal co-produto na producao do biodiesel. Em 2015 foram produzidos 4 milhoes de m 3 de biodiesel a partir da biomassa brasileira, o que g erou mais de 300.000 m 3 de glicerol. O glicerol e aplicado ha decadas em diferentes segmentos industriais, tais como farmaceutico e alimenticio, bem como na industria de cosmeticos e higiene pessoal. Uma aplicacao nova para o glicerol, que vem crescendo nos ultimos anos, e seu uso como um solvente verde em reacoes orgânicas. Neste artigo de revisao sao apresentados e discutidos os trabalhos recentes desenvolvidos no Brasil e no exterior ao uso do glicerol como solvente em sintese orgânica.