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Herein we present an alternative and transition-metal-free procedure to access 3-organoselanylthiochromones and 3-organoselanylchromones from the cyclization reaction between alkynyl aryl ketones and diorganyl diselenides promoted by Oxone®.

A new method was developed for the synthesis of 4-chalcogenyl-1H-isochromen-1-ones through the 6-endo-dig electrophilic cyclization of 2-alkynylaryl esters and diorganyl dichalcogenides under ultrasound irradiation. The reactions were performed under mild conditions, using Oxone as a green oxidant to promote the cleavage of the chalcogen-chalcogen bond in diorganyl diselenides and ditellurides to generate electrophilic species in situ. A total of 25 compounds were selectively obtained after 30-70 min, in good to excellent yields (74-95%). This procedure was extended to prepare 5H-selenopheno[3,2-c]isochromen-5-ones. Additionally, for the first time, the 4-chalcogenyl-1H-isochromen-1-ones were used as substrates in the thionation reaction, using Lawesson's reagent and microwave irradiation under solvent-free conditions, obtaining the thio derivatives in yields of up to 99% in only 15 min.

We describe herein an alternative and transition-metal-free procedure for the access of benzo[b]chalcogenophenes fused to selenophenes via intramolecular cyclization of 1,3-diynes. This efficient protocol involves a double cyclization of 1,3-diynyl chalcogen derivatives promoted by the electrophilic species of organoselenium generated in situ by the oxidative cleavage of the Se-Se bond of dibutyl diselenide using Oxone® in acetonitrile as solvent in an open-flask at 80 °C. In this study, 15 selenophenes with broad substrate scope were prepared in moderate to excellent yields (55-98%) with short reaction times (0.5-3.0 h).

Pyrazoles represent a significant class of heterocyclic compounds that exhibit pharmacological properties. The present study aimed to investigate the antioxidant potential of pyrazol derivative compounds in brain of mice in vitro and the effect of pyrazol derivative compounds in the oxidative damage and toxicity parameters in mouse brain and plasma of mice. The compounds tested were 3,5-dimethyl-1-phenyl-4-(phenylselanyl)-1H-pyrazol (1a), 3,5-dimethyl-4-(phenylselanyl)-1H-pyrazole (2a), 4-((4-methoxyphenyl)selanyl)-3,5-dimethyl-1-phenyl-1H-pyrazole (3a), 4-((4-chlorophenyl)selanyl)-3,5-dimethyl-1-phenyl-1H-pyrazole (4a), 3,5-dimethyl-1-phenyl-4-(phenylthio)-1H-pyrazole (1b), 3,5-dimethyl-4-(phenylthio)-1H-pyrazole (2b), 4-((4-methoxyphenyl)thio)-3,5-dimethyl-1-phenyl-1H-pyrazole (3b), 4-((4-chlorophenyl)thio)-3,5-dimethyl-1-phenyl-1H-pyrazole (4b), and 3,5-dimethyl-1-phenyl-1H-pyrazole (1c). In vitro, 4-(arylcalcogenyl)-1H-pyrazoles, at low molecular range, reduced lipid peroxidation and reactive species in mouse brain homogenates. The compounds also presented ferric-reducing ability as well nitric oxide-scavenging activity. Especially compounds 1a, 1b, and 1c presented efficiency to 1,1-diphenyl-2-picryl-hydrazyl-scavenging activity. Compounds 1b and 1c presented 2,20 -azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)-scavenging activity. In vivo assays demonstrated that compounds 1a, 1b, and 1c (300 mg/kg, intragastric, a single administration) did not cause alteration in the of δ-aminolevulinic acid dehydratase activity, an enzyme that exhibits high sensibility to prooxidants situations, in the brain, liver, and kidney of mice. Compound 1c reduced per se the lipid peroxidation in liver and brain of mice. Toxicological assays demonstrate that compounds 1a, 1b, and 1c did not present toxicity in the aspartate aminotransferase, alanine aminotransferase, urea, and creatinine levels in the plasma. In conclusion, the results demonstrated the antioxidant action of pyrazol derivative compounds in in vitro assays. Furthermore, the results showed low toxicity of compounds in in vivo assays.

We described here our results on the use of thiourea as a ligand in the copper catalysed azide-alkyne cycloaddition (CuAAC) of 2-azidobenzaldehyde with alkynes. Reactions were performed reacting 2-azidobenzaldehyde with a range of terminal alkynes using 10 mol % of copper iodide as a catalyst, 20 mol % of thiourea as a ligand, triethylamine as base, DMSO as solvent at 100 °C under nitrogen atmosphere. The corresponding 2-(1H-1,2,3-triazoyl)-benzaldehydes (2-TBH) were obtained in moderated to excellent yields and according our experiments, the use of thiourea decreases the formation of side products. The obtained compounds were screened for their binding affinity with multiple therapeutic targets of AD by molecular docking: β-secretase (BACE), glycogen synthase kinase (GSK-3β) and acetylcholinesterase (AChE). The three compounds with highest affinity, 5 a (2-(4-phenyl-1H-1,2,3-triazol-1-yl)benzaldehyde), 5 b (2-(4-(p-tolyl)-1H-1,2,3-triazol-1-yl)benzaldehyde), and 5 d (2-(4-(4-(tert-butyl)phenyl)-1H-1,2,3-triazol-1-yl)benzaldehyde) were selected and evaluated on its antioxidant effect, in view of select the most promising one to perform the in vivo validation. Due the antioxidant potential ally to the affinity with BACE, GSK-3β and AChE, compound 5 b was evaluated in a mouse model of AD induced by intracerebroventricular injection of streptozotocin (STZ). Our results indicate that 5 b (1 mg/kg) treatment during 20 days is able to reverse the cognitive and memory impairment induced by STZ trough the modulation of AChE activity, amyloid cascade and GSK-3β expression.

We report herein an alternative method for the synthesis of seleno-dibenzocycloheptenones and seleno-spiro[5.5]trienones through the radical cyclization of biaryl ynones in the presence of diorganyl diselenides, using Oxone as a green oxidizing agent. The reactions were conducted using acetonitrile as the solvent in a sealed tube at 100 °C. The protocol is operationally simple and scalable, exhibits high regioselectivity, and allows the synthesis of 24 dibenzocycloheptenones/spiro[5.5]trienones in yields of up to 99%, 17 of which are unpublished compounds. Additionally, synthetic transformations of the prepared compounds, such as oxidation and reduction reactions, are demonstrated.

A peroxide-mediated protocol for the synthesis of 2-substituted benzothiazoles was developed, starting from bis(o-aminophenyl) disulfides and primary alcohols. Eleven differently 2-substituted benzothiazoles were prepared in moderate to excellent yields using di-tert-butyl peroxide (DTBP) as an oxidant.

A simple and efficient method for the synthesis of 4‑organoselanyl-1H-pyrazoles has been developed, taking place under metal- and halogen-free conditions. Electrophilic species of selenium were easily generated in situ by the reaction of diorganyl diselenides with Oxone® in ethanol as solvent in an open-flask at 70 °C. These electrophilic selenium species were employed in the selenylation/cyclization of α,β-alkynyl hydrazones, giving the title compounds in moderate to excellent yields. The final species of selenium obtained from the reaction of diphenyl diselenide with Oxone® were characterized by 77Se NMR spectroscopy and high-resolution mass spectrometry (HRMS).

This review presents the recent advances involving several applications of five-membered cyclic carbonates and derivatives. With more than 150 references, it covers the period from 2012 to 2020, with special emphasis on the use of five-membered cyclic carbonates as building blocks for organic synthesis and material elaboration. We demonstrate the application of cyclic carbonates in several important chemical transformations, such as decarboxylation, hydrogenation, and transesterification reactions, among others. The presence of cyclic carbonates in molecules with high biological potential is also displayed, together with the importance of these compounds in the preparation of materials such as urethanes, polyurethanes, and flame retardants.

Here, we report the general strategies by which NMR spectroscopy can be used to determine the enantiopurity and absolute configuration of chalcogen containing secondary alcohols, including the evaluation of the use of chiral solvating and chiral derivatizing agents. The BINOL/DMAP ternary complex demonstrated a simple and fast protocol for determining enantiopurity. The drug Naproxen afforded a stable, nonhygroscopic, and readily available chiral derivatizing agent (CDA) for NMR chiral discrimination of chalcogen containing secondary alcohols. The chiral recognition by CDA and chiral solvating agent (CSA) was assessed using 1 H, 77 Se-{1H}, and 125 Te-{1H} NMR spectroscopy. A simple model for the assignment of the absolute configuration from NMR data is presented.

An efficient protocol to access 2-arylselanylbenzo[b]chalcogenophene derivatives through the Cu(I)-catalyzed annulation of vinyl selenides is described. The key vinyl selenides were easily prepared from properly functionalized 1,1-dibromostyrenes and the method allowed the synthesis of 2-arylselanylfurans, -thiophenes, and -selenophenes in moderate to excellent yields.

An efficient copper-catalyzed multicomponent reaction was developed for the synthesis of (arylselanyl)- or (arylsulfenyl)-alkyl-1,2,3-triazolo-1,3,6-triazonines. The products were obtained in moderate to excellent yields via the reaction of o-phenylenediamine, 2-azidobenzaldehyde and different arylchalcogenyl alkynes using catalytic copper iodide in 1,4-dioxane at 100 °C. The reactions tolerated a range of substituents on the arylchalcogenyl alkynes and proved to be an efficient methodology for the combinatorial synthesis of new selenium or sulfur-containing triazonine derivatives.

The use of sonochemistry is described in the organocatalytic enamine–azide [3 + 2] cycloaddition between 1,3-diketones and aryl azidophenyl selenides. These sonochemically promoted reactions were found to be amenable to a range of 1,3-diketones or aryl azidophenyl selenides, providing an efficient access to new ((arylselanyl)phenyl-1H-1,2,3-triazol-4-yl)ketones in good to excellent yields and short reaction times. In addition, this protocol was extended to β-keto esters, β-keto amides and α-cyano ketones. Selanyltriazoyl carboxylates, carboxamides and carbonitriles were synthesized in high yields at short times of reaction under very mild reaction conditions.

A significant number of important acyl-transfer reactions, such as direct acylation, ortho acylation, heteroatom acylation, and a diversity of cyclization reactions using the title compound as a key starting material, have been described in recent years. Just like a sleeping beauty, α-oxocarboxylic acids were awakened from a 17-year sleep to become important reagents in classical and new acylation reactions. The greener characteristic of the coproduct formed in reactions using α-keto acid (only CO2), together with its versatility as a building block in catalytic organic synthesis, accredit it as a candidate to green acylating agent, an alternative to acyl chloride, and other acyl-transfer reagents. This review presents the impressive breakthroughs achieved mainly in the past decade in the development of new catalytic reactions for the formation of C–C, C–N, and C–S bonds using α-keto acids.

We described herein the use of sonochemistry in the organocatalytic enamine-azide [3+2] cycloadditions of β-oxo-amides with a range of substituted aryl azides. These sonochemical promoted reactions were found to be amenable to a range of β-oxo amides or aryl azides, providing an efficient access to new N-aryl-1,2,3-triazoyl carboxamides in good to excellent yields and short times of reaction.

We present here the synthesis of novel (Z)-2-organylselanyl ketoximes by nucleophilic substitution reaction of E/Z mixtures of 2-bromo ketoximes with nucleophilic species of selenium, which were generated in situ by simple cleavage of diorganyl diselenides with NaBH4 using ethanol/THF as solvent. The new 2-organylselanyl ketoximes were synthesized in moderate to good yields and with selectivity for the (Z)-configuration. The synthesized (Z)-2-arylselanylacetophenone oximes were submitted to the Beckmann rearrangement, furnishing the corresponding N-aryl-2-(selanyl)acetamides. (Z)-1-Phenyl-2-(phenylselanyl) ketoxime has antifungal activity against Sphaceloma ampelinum and a good level of antioxidant activity in vitro in DPPH, ABTS, FRAP and lipid peroxidation assays.

We describe a selective method for synthesis of 4-chalcogenylmethyl-1,3-dioxolan-2-ones and 1,3-bis(organylchalcogenyl)propan-2-ols in a short reaction time through stoichiometric control. The use of 3-O-tosyl glycerol 1,2-carbonate and a set of aryl and alkyl diorganyl dichalcogenides afforded the desired products in good to excellent yields. We also describe a synthetic application to 4-chalcogenylmethyl-1,3-dioxolan-2-ones by base promoted the synthesis of 3-(arylchalcogenyl)propane-1,2-diols in excellent yields.

PEG-400 was used as a green and recyclable solvent in an efficient, simple and straightforward method for the synthesis of β-arylthio-α,β-unsaturated esters, ketone and aldehyde through the hydrothiolation of alkynes with arylthiols under base- and catalyst-free conditions. The reactions were performed under mild conditions and furnished selectively the respective ( Z )-β-arylthio-α,β-unsaturated compounds from alkynyl esters and ketone, while from alkynyl aldehyde, the ( E )-stereoisomer was obtained, in good yields and moderate reaction times. PEG-400 was reused in up 5 successive reactions without previous treatment, affording products in comparable yields.

Organochalcogen compounds (containing S, Se and Te) are interesting either for use as an intermediate in the synthesis of complex molecules or for the exploitation of their biological properties. The growing in the number of papers on the synthesis and application of organochalcogen compounds has been accompanied by a concern about how they are prepared. Here, we provide a comprehensive and updated review on recent synthetic methods available for their synthesis using alternative solvents or solvent-free conditions and non-classical energy sources (microwaves irradiation, sonochemistry and mechanochemistry). Organized in fourteen sections, this review brings the more than one hundred alternative methods described so far to access organic compounds containing selenium, tellurium and sulfur.

Herein we describe the reaction between the nucleophilic species of chalcogenium (sulfur, selenium and tellurium) and (R)- and (S)-solketal tosylates to prepare enantiomerically pure bis-1,3-dioxolanylmethyl chalcogenides and dichalcogenides in short reaction times and good yields. Furthermore, the new diselenide 4a was evaluated in the Michael reaction with acrylonitrile, giving (R)-3-[(2,3-dihydroxypropyl)selanyl]propanenitrile 6b after two steps.

We describe herein an efficient protocol to synthesize selanyl-substituted pyrazoles by cyclocondensation and copper-catalyzed direct CH bond selenation reactions. The products were obtained in moderate to excellent yields by the one-pot multicomponent reactions of hydrazines, 1,3-diketones and diorganyl diselenides, using catalytic amounts of copper bromide and bipyridine. These reactions tolerated a range of substituents in the starting materials and proved to be an efficient methodology for combinatorial synthesis of new selenium-containing pyrazoles with potential applications in biological studies.

An alternative green method was described for the synthesis of selanylesters by reactions of acyl chlorides with arylselenols, generated in situ by reaction of diaryl diselenides with hypophosphorous acid (H3PO2) using polyethylene glycol-400 (PEG-400) as the solvent. These reactions proceeded efficiently at room temperature under N2 using a range of acyl chlorides and diaryl diselenides, both containing electron-withdrawing and electron-donating groups, affording the corresponding selanylesters in moderate to excellent yields. Additionally, PEG-400 can be recovered and directly reused for further reactions.

Herein we describe the results on the synthesis and the evaluation of the antioxidant activity of several organochalcogen-containing chrysin derivatives (Se and Te). The semi-synthetic compounds were easily synthesized in good to excellent yields by the reaction of 7-(2-bromoethoxy)-chrysin with nucleophilic organoselenium and organotellurium species. The antioxidant properties of Se- and Te-containing chrysin derivatives were evaluated by three different in vitro assays, the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activities and ferric ion reducing antioxidant power (FRAP). Compounds 4i (which contains the butyltellurium moiety) and 4j (which contains a 4-phenyltellurium moiety) exhibited higher activities than chrysin and the selenium analogues, with compound 4i being the most potent antioxidant.

We describe herein our results on the organocatalytic synthesis and pharmacological properties of 7-chloroquinoline-1,2,3-triazoyl carboxamides. This class of compounds was synthesized in good to excellent yields by the reaction of 4-azido-7-chloroquinoline with a range of β-oxo-amides in the presence of a catalytic amount of pyrrolidine (5 mol%). The obtained compound 3a was screened for anticonvulsant, antinociceptive and anti-inflammatory activities in vivo. The results demonstrated that compound 3a was effective in decreasing the appearance of seizures induced by pilocarpine and pentylenetetrazole. In addition, compound 3a demonstrated antinoceptive and anti-inflammatory properties for combating acute pain. This protocol is an efficient method for the production of new heterocyclic compounds with pharmacological activities.

We present herein our results on the nucleophilic addition of imidazole to a range of arylselanylalkynes by simple heating in DMF without any additives to give ( Z )-1-(1-organyl-(2-arylselanyl)vinyl)-1H-imidazoles. The reactions were performed under mild conditions with a range of arylselanylalkynes in good yields and with high regio- and stereoselectivity to give the respective (Z)-arylselanyl alkene as the only isomer.

We describe herein the use of glycerol as an efficient and recyclable solvent for the addition of thiols to nonactivated alkenes. The catalyst-free reactions take place easily using glycerol at room temperature or heating and the corresponding linear thioethers were obtained in good to excellent yields. The method was used to synthesize new sulfur-containing eugenols, which were tested for their antioxidant activities. The semisynthetic thio-derivatives were more effective in inhibition of induced lipid peroxidation compared to the precursor eugenol and the synthetic antioxidant butylated hydroxyanisole.

Imine-modified silicas were synthesized by the reaction of the essential oil of Eucalyptus citriodora , 3-aminopropyltriethoxysilane and tetraethylorthosilicate by different methods. The imine supported on silica was characterized by FT-IR-spectroscopy using the attenuated total reflection (ATR) technique, the Brunauer–Emmett–Teller (BET) method and thermogravimetric analysis (TGA). These silicas have shown a large amount of organic matter incorporated on the surface, which affects their textural properties. The hydrolysis reaction of the imine-modified silica leads to the formation of products different from those expected.

A convenient approach to the Cu-catalyzed coupling of diphenyl disulfide and diphenyl ditelluride with vinyl bromides using a recyclable catalytic system and glycerol as a green solvent is described. This protocol was efficiently used in the preparation of vinyl sulfides and vinyl tellurides with a variety of substituents in good yields and stereoselectively. The solvent/catalyst system was directly reused for four cycles without loss of activity.