Direct Electrophilic Selenocyanation And Alkylation Of Electron-Rich Arenes Based On Mechanochemistry

The increasingly severe environmental problems in contemporary society have become the shackles restricting the development of the economy.Numerous chemists have been devoted to developing the eco-friendly green synthetic strategies to access valuable organic compounds.Among them,mechanochemistry has attracted increasing attention due to the advantages of short reaction time and solvent-free conditions.This thesis focuses on promoting sustainable development by employing green strategies for direct electrophilic selenocyanation and alkylation of electron-rich arenes enabled by mechanochemistry.The approach includes direct electrophilic selenocyanation of(hetero)arenes and C3-alkylation of 2-indolymethanols with donor-acceptor cyclopropanes facilitated by mechanochemical synthesis.The thesis is divided into four chapters,the main contents of which are explained below:The first chapter is the introduction,which mainly introduces the application of mechanochemistry and reviews the synthetic methods to access organoselenocyanates.Besides,the recent progress of C3-alkylation of electron-rich arenes with donor-acceptor cyclopropanes is also reviewed.The significance of the research topic and the design ideas of this thesis are also expounded through analyzed the recent progress in this field.The second chapter mainly introduces the solid-state electrophilic selenocyanation reaction of(hetero)arenes by using mechanochemistry.Besides,the condition optimization,substrate scope investigation,gram-scale synthesis and further derivations of products were also studied.The optimal conditions are confirmed through condition optimization,namely: Nselenocyanatophthalimide is used as the electrophilic selenocyanating reagent,and the reaction mixture is ground and reacted for 60 minutes at 35 Hz,35 examples of various selenocyanates were obtained in moderate to excellent yields(33-99%).Additionally,the corresponding selenocyanates were characterized by nuclear magnetic resonance,single crystal XRD and other technical means.Furthermore,the mechanism was also proposed.The third chapter mainly introduces the synthetic route,the condition optimization process,substrate scope,gram-scale reaction of the title reaction and further transformations of product.The optimal reaction conditions were established as follows: scandium trifluoromethanesulfonate(10 mol%)and tetra-triphenylphosphine palladium(5 mol%),dichloromethane as the LAG reagent,99 min at the frequency of 35 Hz.20 examples of 3-substituted 2-indolymethanols were delivered in moderate to good yields(45-86%).Besides,the corresponding products were characterized by NMR and XRD.In the fourth chapter,the conclusion of this paper was summarized.This paper mainly introduces the construction of aromatic selenocyanate compounds through direct electrophilic selenocyanation of electron-rich arenes using mechanochemistry and the synthesis of 3-substituted 2-indolymethanols through synergistic palladium/scandium catalyzed C3-alkylation of 2-indolymethanols with donor-acceptor cyclopropanes enabled by mechanochemical synthesis.This protocol has the advantages of short reaction time,efficient and easy to operate,and accords with the concept of green sustainable synthetic chemistry.These strategies could also enrich the selenocyanation and alkylation of electron-rich arenes research field and further promote the application of mechanochemistry in the field of organic synthesis.