Polycyclic Arene-Fused Selenophenes via Site Selective Selenocyclization of Arylethynyl Substituted Polycyclic Arenes

Abstract

Arene-fused selenophenes were synthesized by a redox neutral process from arylethynyl substituted polycyclic arenes using selenium powder in refluxing N-methyl-2-pyrrolidone (NMP) with the assistance of the residual water in NMP as a catalytic proton source. The site-selective nature of this selenocyclization produces trans-alkenes as a competitive product, which is dependent on the π-electron donation ability of polycyclic arenes and the kind of arylethynyl group attached to it. DFT calculations were performed to understand the site selectivity in the selenophene formation reaction. The HOMO coefficient on the carbon adjacent to carbon having arylalkyne substituent of the polycyclic arene correlates with the selenocyclization tendency of the substrate. The wavelength of absorption and emission and quantum yield of emission increase with increasing the number of fused benzene rings in the polycyclic unit (from naphthalene to pyrene).

CS2/KOH System-Promoted Stereoselective Synthesis of (E)-Alkenes from Diarylalkynes and a “Hidden” Zinin-Type Reduction of Nitroarenes into Arylamines

“…In this scenario, sulfur and selenium chemistry have presented attractive transition metal-free protocols to promote semireduction of alkynes with high E -stereoselectivity, where different sulfur salts such as Na 2 S and potassium ethyl xanthate were described as effective reducing agents, employing water as an environmentally benign hydrogen source. Moreover, some of these systems have also been applied to reduce α,β-unsaturated carbonyl compounds and, very recently, the combination of CS 2 with t -BuOK or NaOH also enabled this type of reaction using DMSO or water as hydrogen sources.…”