Alisson R. Rosário

Synthesis of 2,3-dihydroselenophene and selenophene derivatives by electrophilic cyclization of homopropargyl selenides.

The synthesis of several highly functionalized 2,3-dihydroselenophenes from homopropargyl selenides via electrophilic cyclization is described. Electrophiles such as I(2), ICl, and PhSeBr were used in a simple process employing CH(2)Cl(2) as solvent at room temperature, which gave the cyclized products in high yields. 4-Iodo-2,3-dihydroselenophenes obtained by this methodology were submitted to a dehydrogenation reaction using 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) to give 3-iodoselenophenes. 4-Iodo-5-phenyl-2,3-dihydroselenophene was also submitted to the thiol copper-catalyzed and Heck-type reactions giving the desired products under mild reaction conditions.

The potential antioxidant activity of 2,3-dihydroselenophene, a prototype drug of 4-aryl-2,3-dihydroselenophenes.

Here we present our results in palladium cross-coupling reaction of aryl boronic acids with 4-iodo-2,3-dihydroselenophene derivatives. The cross-coupled products were obtained in satisfactory yields. A dehydrogenation of 4,5-diphenyl-2,3-dihydroselenophene was activated by DDQ and the 2,3-diarylselenophene was obtained in good yield. Regarding the antioxidant activity, the selenophene derivative 3a was effective in counteracting lipid and protein oxidation as well as scavenging ABTS radical. The findings of the present study indicate that 3a is a prototype for future drug development programs to treat disorders mediated by reactive oxygen species.

Cyclization of Homopropargyl Chalcogenides by Copper(II) Salts: Selective Synthesis of 2,3‐Dihydroselenophenes, 3‐Arylselenophenes, and 3‐Haloselenophenes/thiophenes

Copper(II) halide mediated cyclization of homopropargyl chalcogenides gave three types of chalcogenophene derivatives. Selective product formation was achieved by controlling solvent, temperature, and atmosphere. By using CuBr2 and 1,2-dichloroethane at room temperature under ambient atmosphere, 4-bromo dihydroselenophene derivatives were obtained, whereas CuBr2 and 1,2-dichloroethane at reflux gave selectively 2-substituted selenophenes. When 1,2-dichloroethane was replaced by dimethylacetamide, 3-halo-selenophenes were obtained exclusively. The versatility of chalcogenophenes was also studied by reaction of 3-haloselenophenes with terminal alkynes under Sonogashira conditions affording the cross-coupled products. In addition, the reaction of 3-haloselenophenes with boronic acids gave the corresponding Suzuki-type products in good yields.