"Green Is the Color": An Update on Ecofriendly Aspects of Organoselenium Chemistry.

Organoselenium compounds have been successfully applied in biological, medicinal and material sciences, as well as a powerful tool for modern organic synthesis, attracting the attention of the scientific community. This great success is mainly due to the breaking of paradigm demonstrated by innumerous works, that the selenium compounds were toxic and would have a potential impact on the environment. In this update review, we highlight the relevance of these compounds in several fields of research as well as the possibility to synthesize them through more environmentally sustainable methodologies, involving catalytic processes, flow chemistry, electrosynthesis, as well as by the use of alternative energy sources, including mechanochemical, photochemistry, sonochemical and microwave irradiation.

Light-Mediated Seleno-Functionalization of Organic Molecules: Recent Advances.

Organoselenium compounds constitute an important class of substances with applications in the biological, medicinal and material sciences as well as in modern organic synthesis, attracting considerable attention from the scientific community. Therefore, the construction of the C-Se bond via facile, efficient and sustainable strategies to access complex scaffolds from simple substrates are an appealing and hot topic. Visible light can be regarded as an alternative source of energy and is associated with environmentally-friendly processes. Recently, the use of visible-light mediated seleno-functionalization has emerged as an ideal and powerful route to obtain high-value selenylated products, with diminished cost and waste. This approach, involving photo-excited substrates/catalyst and single-electron transfer (SET) between substrates in the presence of visible light has been successfully used in the versatile and direct insertion of organoselenium moieties in activated and unactivated C(sp3 )-H, C(sp2 )-H, C(sp)-H bonds as well as C-heteroatom bonds. In most cases, ease of operation and accessibility of the light source (LEDs or commercial CFL bulbs) makes this approach more attractive and sustainable than the traditional strategies.

Catalytic chalcogenylation under greener conditions: a solvent-free sulfur- and seleno-functionalization of olefins via I2/DMSO oxidant system.

Herein, we report a solvent- and metal-free methodology for the alkoxy-chalcogenylation of styrenes, using molecular iodine as a catalyst, DMSO as a stoichiometric oxidant, and different nucleophiles under microwave irradiation. This eco-friendly approach afforded the desired products in good to excellent yields in only 10 min. In addition, using the same protocol, we carried out the cyclization reaction of relevant molecules, such as lapachol derivatives.

A solvent- and metal-free synthesis of 3-chacogenyl-indoles employing DMSO/I2 as an eco-friendly catalytic oxidation system.

Herein, we describe a solvent- and metal-free method for the synthesis of 3-chalcogenyl-indoles from indoles and diorganyl dichalcogenides using an equivalent amount of DMSO as an oxidant, under catalysis by molecular iodine. This mild and eco-friendly approach allowed the preparation of a wide range of 3-selenyl- and 3-sulfenyl-indoles in good to excellent yields.