This review is dedicated to the memory of Prof. Nicola Petragnani, a pionner in the chemistry of selenium and tellurium in Brazil, who passed away on December 5, 2015.Organochalcogen compounds (containing S, Se and Te) are interesting either for use as an intermediate in the synthesis of complex molecules or for the exploitation of their biological properties. The growing in the number of papers on the synthesis and application of organochalcogen compounds has been accompanied by a concern about how they are prepared. Here, we provide a comprehensive and updated review on re-cent synthetic methods available for their synthesis using alternative solvents or solvent-free conditions and non-classical energy sources (microwaves irradiation, sonochemistry and mechanochemistry). Organized in fourteen sections, this review brings the more than one hundred alternative methods described so far to access organic compounds containing selenium, tellurium and sulfur.[a] Prof.
We describe here for the first time the synthesis of isochromenones fused to selenophenes. 5H‐Selenopheno[3,2‐c]isochromen‐5‐ones were obtained through a double intramolecular cyclization of methyl 2‐(organyl‐1,3‐diynyl)benzoate promoted by electrophilic species of selenium generated in situ by the reaction of dialkyl diselenides with Oxone®, using ethanol as solvent. The reactions were conducted satisfactorily under mild conditions, using a range of 1,3‐diynes and dialkyl diselenides as substrates. A total of sixteen unprecedent 5H‐selenopheno[3,2‐c]isochromen‐5‐ones were selectively obtained in moderate to good yields (40–86%) under reflux in an open flask and in short reaction times (1.0–2.5 h).magnified image
This review presents the recent advances involving several applications of five-membered cyclic carbonates and derivatives. With more than 150 references, it covers the period from 2012 to 2020, with special emphasis on the use of five-membered cyclic carbonates as building blocks for organic synthesis and material elaboration. We demonstrate the application of cyclic carbonates in several important chemical transformations, such as decarboxylation, hydrogenation, and transesterification reactions, among others. The presence of cyclic carbonates in molecules with high biological potential is also displayed, together with the importance of these compounds in the preparation of materials such as urethanes, polyurethanes, and flame retardants.
We described herein the use of imidazolium ionic liquids [bmim]PF 6 and [bmim]BF 4 in the selective, metal and catalyst-free synthesis of unsymmetrical diaryl selenides by electrophilic substitution in arylboron reagents with arylselenium halides (Cl and Br) at room temperature. This is a general substitution reaction and it was performed with arylboronic acids or potassium aryltrifluoroborates bearing electron-withdrawing or electron-donating groups, affording the corresponding diaryl selenides in good to excellent yields. The ionic liquid [bmim] [PF 6 ] was easily recovered and utilized for further substitution reactions.
We describe herein an alternative method for the selenomethoxylation of unactivated alkenes using Oxone® as a stoichiometric oxidant. The electrophilic species of selenium were easily generated in situ by the reaction of diorganyl diselenides with Oxone®. By this efficient and simple approach, β‐methoxy‐selenides were obtained in moderate to excellent yields at room temperature in an open flask, starting from alkenes by using methanol as both nucleophile and solvent. When a mixture of H2O/CH3CN was employed as the solvent, β‐hydroxy‐selenides were selectively obtained under mild conditions.
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