Raquel G. Jacob

Synthesis of Vinyl Selenides

The versatility and utility of vinyl chalcogenides in organic synthesis is well documented through the publication of a number of review articles1 and books.2 The development of new methods for the preparation and applicability of vinyl sulfides,3a-c sulfones,3d and tellurides4 was recently revised. * Corresponding author. Phone/fax: +55 53 3275 7533. E-mail: gelson_perin@ufpel.edu.br. Chem. Rev. 2009, 109, 1277–1301 1277

Glycerol as a recyclable solvent for copper-catalyzed cross-coupling reactions of diaryl diselenides with aryl boronic acids

We describe herein the use of glycerol as the solvent in the copper-catalyzed cross-coupling reaction of diaryl diselenides with arylboronic acids using CuI and DMSO as additive. This cross-coupling reaction was performed with diaryl diselenides and arylboronic acids bearing electron-withdrawing and electron-donating groups, affording the corresponding diaryl selenides in good to excellent yields. The glycerol–CuI mixture can be directly reused for further cross-coupling reactions.

Essential oil of the leaves of Eugenia uniflora L.: Antioxidant and antimicrobial properties

Essential oil (EO) of the leaves of Eugenia uniflora L. (Brazilian cherry tree) was evaluated for its antioxidant, antibacterial and antifungal properties. The acute toxicity of the EO administered by oral route was also evaluated in mice. The EO exhibited antioxidant activity in the DPPH, ABTS and FRAP assays and reduced lipid peroxidation in the kidney of mice. The EO also showed antimicrobial activity against two important pathogenic bacteria, Staphylococcus aureus and Listeria monocytogenes, and against two fungi of the Candida species, C. lipolytica and C. guilliermondii. Acute administration of the EO by the oral route did not cause lethality or toxicological effects in mice. These findings suggest that the EO of the leaves of E. uniflora may have the potential for use in the pharmaceutical industry.

Green Michael addition of thiols to electron deficient alkenes using KF/alumina and recyclable solvent or solvent-free conditions

A general, clean and easy method for the conjugated addition of thiols to citral promoted by KF/Al2O3 under solvent-free or using glycerin as recyclable solvent at room temperature is described. It was found that the solvent-free protocol is applicable to the direct reaction of thiophenol with the essential oil of lemon grass (Cymbopogon citratus) to afford directly 3,7-dimethyl-3-(phenylthio)oct-6-enal, a potential bactericide agent. The method was extended to other electron-poor alkenes with excellent results. For the solvent-free protocol, the use of microwave irradiation facilitated the procedure and accelerates the reaction. The catalytic system and glycerin can be reused up to three times without previous treatment with comparable activity.

Synthesis of ketene (S, Te)acetals and their transformation into Z-α-phenylthio-α,β-unsaturated aldehydes

Abstract Reaction of thiomethyl phosphonates with aryl (or butyl) tellurenyl halides and aldehydes under basic conditions provides moderate to good yields of ketene thio (telluro) acetals, with vinylic sulfides being byproducts of this transformation. Tellurium-lithium exchange by reaction with n-BuLi yielded vinyl organolithium species, which were captured with several electrophiles. In the case of DMF, Z-α-phenylthio-α,β-unsaturated aldehydes were obtained.

Green synthesis of (−)-isopulegol from (+)-citronellal: application to essential oil of citronella

A simple green and efficient method has been developed for the synthesis of (−)-isopulegol from (+)-citronellal in the presence of a solid supported catalyst (SiO2/ZnCl2), under solvent-free conditions and MW irradiation. It was also found that the same technology is applicable to the direct preparation of (−)-isopulegol from the essential oil of citronella (Cymbopogon nardus, growing in southern Brazil) in excellent yield.

Clean and atom-economic synthesis of octahydroacridines: application to essential oil of citronella

Abstract A green and efficient method for the synthesis of octahydroacridine (OHA) has been developed by a simple one-pot hetero-Diels–Alder reaction starting from (+)-citronellal and N -arylamines in the presence of a solid supported catalyst (SiO 2 /ZnCl 2 ), under MW irradiation and without any solvent. The method was used in the direct preparation of OHA from citronella oil in good yield.

In vitro antioxidant activity and in vivo antidepressant-like effect of α-(phenylselanyl) acetophenone in mice.

In this study, the antioxidant and antidepressant-like effects of α-(phenylselanyl) acetophenone (PSAP), an organoselenium compound, were investigated. To assess the in vitro antioxidant properties, PSAP was evaluated in four test systems (DPPH, ABTS, FRAP and inhibition of lipid peroxidation). PSAP (100-500 μM) showed potent antioxidant activity and protected against lipid peroxidation. Additionally, we investigated whether PSAP, when administered in mice (100, 200 and 400mg/kg, per oral, p.o.), could cause acute toxicity. Our results demonstrated that PSAP did not cause the death of any animal, significantly reduce body weight or cause any oxidative tissue stress following treatment. This study also evaluated the effect of PSAP (0.1-10 mg/kg, p.o) on mice in a forced swim test (FST) and tail suspension test (TST), assays that are predictive of depressant activity and motor activity in the open-field. PSAP (5-10 mg/kg) significantly reduced immobility time in the FST and TST without affecting motor activity. In addition, the antidepressant-like effect caused by PSAP (5m/kg, p.o) in mice during the TST was dependent on an interaction with the serotonergic system (5-HT(1A) receptors), but not with the noradrenergic, dopaminergic or adenosinergic system. Together, these results suggest that PSAP possesses antioxidant and antidepressant-like properties and may be of interest as a therapeutic agent for the treatment of depressive disorders.

Synthesis of diaryl selenides using electrophilic selenium species and nucleophilic boron reagents in ionic liquids

We described herein the use of imidazolium ionic liquids [bmim]PF6 and [bmim]BF4 in the selective, metal and catalyst-free synthesis of unsymmetrical diaryl selenides by electrophilic substitution in arylboron reagents with arylselenium halides (Cl and Br) at room temperature. This is a general substitution reaction and it was performed with arylboronic acids or potassium aryltrifluoroborates bearing electron-withdrawing or electron-donating groups, affording the corresponding diaryl selenides in good to excellent yields. The ionic liquid [bmim][PF6] was easily recovered and utilized for further substitution reactions.

Sonochemistry: An efficient alternative to the synthesis of 3-selanylindoles using CuI as catalyst

Ultrasonic (US) irradiation was successfully used as an alternative energy source to prepare 3-selanylindoles through the direct selanylation of indoles with diorganyl diselenides using CuI (20 mol%) as catalyst and DMSO as the solvent. By using this US-promoted reaction, eleven 3-organylselanylindoles were prepared selectively and in good yields. A comparative study between the reactions under conventional heating, microwave and ultrasound irradiations was performed, and it was observed advantage in using US over the other heating systems.