Synthesis of 3,4-Bis(Butylselanyl)Selenophenes and 4-Alkoxyselenophenes Promoted by Oxone®

Abstract

We describe herein an alternative transition-metal-free procedure to access 3,4-bis(butylselanyl)selenophenes and the so far unprecedented 3-(butylselanyl)-4-alkoxyselenophenes. The protocol involves the 5-endo-dig electrophilic cyclization of 1,3-diynes promoted by electrophilic organoselenium species, generated in situ through the oxidative cleavage of the Se-Se bond of dibutyl diselenide using Oxone® as a green oxidant. The selective formation of the title products was achieved by controlling the solvent identity and the amount of dibutyl diselenide. By using 4.0 equiv of dibutyl diselenide and acetonitrile as solvent at 80 °C, four examples of 3,4-bis(butylselanyl)selenophenes were obtained in moderate to good yields (40–78%). When 3.0 equiv of dibutyl diselenide were used, in the presence of aliphatic alcohols as solvent/nucleophiles under reflux, 10 3-(butylselanyl)-4-alkoxyselenophenes were selectively obtained in low to good yields (15–80%).

Recent Developments in the Synthesis of Organoselenium Compounds Based on the Reactions of Organic Diselenides with Acetylenes

“…Over the past few decades, this green oxidative reagent has become a powerful tool in organic synthesis [116]. Recently, potassium peroxymonosulfate was successfully used in a number of promising transformations with the formation of valuable organoselenium compounds including heterocyclic products [118][119][120][121][122][123][124][125][126][127][128].…”

“…Perin, Lenardão, and co-workers developed a transition metal-free method for the synthesis of 3,4-bis(butylselanyl)selenophenes via the electrophilic cyclization of 1,3-diynes with dibutyl diselenide using Oxone ® as a green oxidant and acetonitrile as the solvent (Scheme 36) [126].…”

“…The synthesis of 3-(butylselanyl)-4-alkoxyselenophenes was developed for the first time starting from several 1,3-diynes and dibutyl diselenide (Scheme 36) [126]. The reaction was carried out in the presence of Oxone ® using aliphatic alcohols as the solvent and nucleophilic reagents.…”

Applications of Oxone® in Organic Synthesis: An Emerging Green Reagent of Modern Era

“…[341] Therefore, in quest for the generation of new methods to these vital molecules" Hellwig et al recently developed a transitionmetal-free method for accessing 3,4-bis(butylselanyl)selenophenes 463a-b or 464c-ein moderate to good yields by electrophilic cyclization of 1,3-diynes 461 with dibutyldiselenide 462 using oxone in acetonitrile or alcoholic solvents (Scheme 145). [342] A plausible mechanism for the formation of 3-(butylselanyl)-4-ethoxy-2,5-di-4-tolylselenophene 463 and 3,4-bis(butylselanyl)selenophene 464 involves two steps as can be inspected from the Scheme 145, first one is the formation of electrophiles and other include the cyclization as displayed clearly in the Scheme 146.…”

Recent Advances in the Oxone-Mediated Synthesis of Heterocyclic Compounds

“…As previously observed, the protocol was not suitable to diphenyl disulfide 42a, whereas 3-(phenyltellanyl)-2,5-diphenyltellurophene 62f was obtained in only 28% by the reaction between 65a and diphenyl ditelluride 41a under the optimal conditions (Scheme 44). In 2021, some of us reported an Oxone/dibutyl diselenide-promoted 5-endo-dig electrophilic cyclization of 1,3-diynes 66, to access selectively 3,4-bis(butylselanyl)selenophenes 67 and 4-alkoxyselenophenes 68 (Scheme 46) [48]. The selectivity in the formation of the products 67 and 68 was achieved by controlling the solvent (MeCN or ROH) and the dibutyl diselenide 21f amount (2 equiv or 1.5 equiv).…”