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We describe here for the first time the synthesis of 2-(chalcogenyl)-3

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).

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®. The use of mild reaction conditions, efficiency and generality are characteristics of this new approach, which was suitable to convert different diselenides and 2-functionalized chalcogenoalkynes into a total of twenty-two 2,3-bis-organochalcogenyl-benzo[b]chalcogenophenes, eighteen of which were synthesized for the first time. The new compound 2-(butylselanyl)-3-(phenylselanyl)benzofuran was used as a substrate in the Pd-catalyzed reaction with phenylacetylene to access the Sonogashira's coupling derivative in good yield.

A convenient synthesis of 1-(2-organylchalcogenylethynyl)-2-butylselenanylbenzenes was established taking advantage of the selective reaction of 1-(2,2-dibromovinyl)-2-butylselenanylbenzenes with thiols or diorganyl diselenides. The new 1-(2-chalcogenylethynyl)-2-butylselenanylbenzenes were prepared in good yields and used as precursors of 2-organylchalcogenylbenzo[b]selenophenes via electrophilic cyclization using I2, Br2 or PhSeBr as electrophiles. Different classes of new 3-substituted- (3-iodo, 3-bromo, 3-phenylselenanyl) benzo[b]selenophenes were prepared in good yields. The synthetic application of the obtained products was demonstrated employing the benzo[b]selenophenes in Suzuki and Sonogashira cross-coupling reactions.

The selenophene derivatives are an important class of selenium-based heterocyclics. These compounds play an important role in prospecting new drugs, as well as in the development of new light-emitting materials. During the last years, several methods have been emerging to access the selenophene scaffold, employing a diversity of cyclization-based synthetic strategies, involving specific reaction partners and particularities. This review presents a comprehensive discussion on the recent advances in the synthesis of selenophene-based compounds, starting from different precursors, highlighting the main differences, the advantages, and limitations among them.