An efficient synthesis of 2-chalcogen-3-substituted-benzo[b]furan compounds has been accomplished via electrophilic cyclization reaction of 2-chalcogenealkynyl anisoles using I(2), ICl, Br(2), and PhSeBr as electrophile sources. The product distributions were strongly dependent on the nature of substituents in the aromatic ring of anisole and on the chalcogen atom directly bonded to the triple bond. The 2-chalcogen-3-iodo-benzo[b]furans obtained smoothly underwent conversion to more complex structures of benzo[b]furan derivatives via palladium- or copper-catalyzed cross-coupling reaction with thiols, diphenyl diselenides, and zincates.

We present here the synthesis and antidepressant-like action of a series of 2,5-disubstituted-3-(organoseleno)-selenophenes prepared by a novel synthetic route, the FeCl(3)-diorganyl dichalcogenide-mediated intramolecular cyclization of (Z)-chalcogenoenynes. The cyclized products were obtained in good yields. The results showed that 2c, 2d, 2e and 2o, evaluated in the mouse forced-swimming test, elicited an antidepressant-like activity. The studies clearly show that the phenyl group at the 2-position and an organoselenium group at the 3-position of the selenophene ring are essential for the antidepressant-like activity of selenophenes. A close inspection of the results also revealed that the fluorophenyl portion in the organoselenium group is fundamental for the antidepressant-like action of this class of organochalcogens.

We report here an alternative and tunable metal-free synthesis of benzo[b]chalcogenophenes via the electrophilic cyclization of 2-functionalized chalcogenoalkynes promoted by Oxone®.

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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).

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Herein we report the use of ultrasonic irradiation (US) in the synthesis of six new semi-synthetic selenium-containing chrysin derivatives by a simple and effective methodology utilizing CuI as catalyst, in good to excellent yields (60-89%). It was observed that US accelerates the reaction compared to conventional heating with excellent selectivity for diselenylated products. Compounds were tested for their antioxidant and anticancer activities in vitro and it was observed that the presence of selenium in the A-ring of chrysin enhanced both antioxidant and anticancer properties. Semi-synthetic 6,8-bis(o-tolylselanyl)-chrysin 3b has the best radical scavenging activity of DPPH (I: 39.79µM) and ABTS (IC: 6.5µM) radicals. Similarly, in the Reactive Species (RS) assay, 3b showed high antioxidant activity in mice cortex (IC: 5.67µM), whereas 6,8-bis(p-anisoylselanyl)-chrysin 3c was the more active in the hippocampus (IC: 5.63µM). The Se-chrysins were effective in prevention of lipid peroxidation, highlighting 6,8-bis(p-fluorophenylselanyl)-chrysin 3d in cortex (IC: 0.54µM) and 3b in hippocampus (IC: 0.27µM). In addition, 3d was effective in inhibiting human lung adenocarcinoma (A549) cells growth, with a IC of 19.9µM after 72h of treatment, while 6,8-bis(p-anisoylselanyl)-chrysin 3c presented the higher antiproliferative activity after 48h of treatment (IC of 41.4µM).

Cucurbit­[7]­uril (CB7) catalyzes the acid hydrolysis of alkoxyphenyldioxolanes bearing both neutral and cationic alkoxy groups. The magnitude of the catalytic effect depends on the dioxolane structure, as reflected by both the CB7 binding constants and the catalysis rate constants. However, there is no clear relationship in such a way that increasing the binding affinity (cationic dioxolanes or large alkoxy groups) does not enhance the catalytic effect. The A-1 mechanism for dioxolane hydrolysis involves the protonation and formation of a carbocation by protonated dioxolane ring opening. Supramolecular catalysis takes place through the formation of the ternary complex dioxolane@CB7@H3O+, where the hydronium ion is stabilized by hydrogen bonding with the carbonyl groups of the CB7 portal. The ternary complex evolves to a binary complex by protonation of dioxolane and release of a water molecule. It is important to note that these structures are only stable in the presence of CB7 and not in bulk water. The carbocation is formed by opening the protonated dioxolane group in the rate-determining step. The distance between the carbonyl portal of CB7 and the dioxolane group in the ternary and binary complexes (protonated and carbocation) increases with the alkyl chain length, resulting in the loss of the CB7 stabilizing effect and decrease in catalytic efficiency. The existence of two recognition motifs with cationic dioxolanes results in the formation of both 1:1 and 2:1 complexes with different catalytic properties.