Studies On The Cascade Cyclization Reaction Through Radical Process

Sulfonylated/selenated cyclic compounds are important class of bioactive molecules extensively found in pharmacologically active molecules.Traditional methods for synthesizing sulfonylated/selenated cyclic compounds have many limitations,such as harsh reaction conditions,poor tolerance of functional groups,and requirement of the pre-activated substrate.Therefore,development of concise methods for building such structures is highly valuable.In recent years,radical cascade reactions are highly valuable for the preparation of various functionalized cyclic compounds with high efficiency due to multiple chemical bonds can be constructed in one step.Thus,in this thesis,a series of concise and efficient methods for constructing a variety of novel sulfonylated/selenated cyclic compounds via a radical cascade cyclization is described,providing reliable pathways for the discovery of lead compounds in medicinal chemistry.The main results obtained are as follows:（1）A concise K₂S₂O₈-promoted cyclization cascade process for the preparation of 4-sulfonated cyclopenta[gh]phenanthridines from 2-alkynylnitriles and sodium sulfinates under transition metal free conditions has been established.This transformation involving the formation of C-C,C-S,and C-N bonds in one pot features tolerance of various functional groups and high atom economy.This method provides a reliable way for the efficient synthesis of sulfonylated fused heterocycles.（2）A three-component sulfonylative spirocyclization of indolyl ynones with aryldiazonium salts and DABCO?（SO₂）₂ has been explored,providing a series of sulfonated spiro[cyclopentenone-1,3′-indole]derivatives in moderate to good yields under metal and additive free conditions.This protocol was initiated by in-situ generated arylsulfonyl radical,which involving a radical-induced dearomative cascade cyclization accompanied by the insertion of sulfur dioxide and features tolerance of various functional groups.（3）A photoredox-catalyzed sulfonylation of N-allylamides with DABCO?（SO₂）₂in the presence of visible light has been described,leading to a range of sulfonated2-oxazolines in moderate to good yields.This transformation involves sequential intermolecular sulfonylation of alkenes and intramolecular cyclization via a radical process.This protocol features good functional group compatibility and mild conditions.2-Oxazolines could be efficiently converted into sulfonylatedβ-amino alcohol,which provides a new way for the synthesis ofβ-amino alcohol derivatives.（4）A visible-light induced dearomative cascade cyclization of biaryl ynones with diselenides under oxygen atmosphere has been explored,giving a series of selenated spiro[5.5]trienones in moderate to good yields.The Se-Se bond in diselenides cleaved to generate seleno radicals under visible light irradiation.This method provides a novel and step-economical protocol for the synthesis of spiro[5.5]trienones.This protocol features good functional group compatibility under the photocatalyst-free conditions.This method provides a new and green strategy for the synthesis of selenated spirocyclic.