Study On The Synthesis Of Organoselenium Compounds Employing Isocyanides

Selenium is one of the trace elements needed by human body.Organoselenium compounds are widely used in organic synthesis,biology,pesticides,materials and other fields.Isocyanides have been widely employed in the construction of nitrogen-containing organic compounds due to its unique reactivity.In recent years,the rapid development of isocyanide chemistry has provided new ideas for the synthesis of organoselenium compounds,which greatly enriched the reaction types of selenium chemistry,and led to more diverse nitrogen-containing organoselenium compounds being constructed.At the same time,the concept sustainable development of modern science has put forward higher requirements for us.Therefore,the facile synthesis of organoselenium compounds with the employment of isocysnide was studied in this paper.In the first part,we developed a method for the synthesis of 3-aryl-5-amino-1.2,4-selenodiazole derivatives under metal-free conditions by cascade cyclization with isocyanide,selenium powder and amines.The reaction proceeds under mild conditions with O2 as green oxidant and no extra oxidants are required.The strategy has the advantages of mild conditions.simple reagents and no need of metal catalysts.The method can b e used for modification of bioactive molecules and provides a new method for synthesis of novel organic selenium compounds with potential biological and pharmaceutical activities.In the second part,we have successfully synthesized a series of new highly active selenium reagents(selenosulfonates)and developed a metal-free multi-component reaction involving isocyanide,selenosulfonates and water to construct N-substituted selenocarbamate compounds with excellent functional group tolerance.The reaction has the advantages of mild conditions,simple reagents and catalyst-free condition.Selenosulfonates,as highly active selenium reagents,have been successfully applied to the facile synthesis of other organoselenium compounds with isocyanides.Detailed mechanism studies showed that the reaction underwent a radical-chain reaction process.In the third part,we obtained a series of N-(selenocarbonate)benzimidazolinone derivatives by cascade cyclization of aryl o-diisocyanides with Se-alkyl selenosulfonates in medium to excellent yields,and showed excellent functional group tolerance.One C-N bond,one C-Se bond and two C=O bonds were constructed in one step.The reaction has the advantages of mild conditions,easy operation and catalyst-free condition.In addition,the synthesis of N-(selenocarbonate)benzimidazolinone derivatives is expected to provide new research objects for the development of novel bioactive molecules.In the fourth part,as expanded applications of selenosulfonates and thiosulfonates,we innovatively applied them to the cross-coupling reactions with unactivated bromoalkanes.We developed a method for the construction of unsymmetric alkyl sulfides and selenides by nickel-catalyzed reductive coupling reactions for the first time.The reactions proceed with excellent chemoselectivity under mild reaction conditions,thus tolerating a wide range of functional groups.Additionally,the reaction is amenable to scale up with low catalyst loading,which enables its applications in agrochemical and pharmaceutical industries as well as material science.Detailed mechanistic studies provided strong evidence for a facile homolytic C-Br cleavage,and a kinetically relevant nickel reduction.