Visible Light Promote Sulfoxidation And Free Radical Addition Reactions

Reactions triggered by light are unique synthetic methods to chemists.Photoinduced redox processes using visible light in conjunction with sensitizers offera great variety of useful catalytic transformations in the realm of organic synthesis.The recent literature reports have shown that this field is expanding substantially.Visible-light-promoted reaction becomes an important area in new organic reactionsdevelopment. This thesis research work focuses on the development of visible lightpromoted new synthetically useful methodolodies. We have developed a simplemetal-free catalytic sulfoxidation under visible light and air, and four photoredoxradical addition/substituation reactions, including intermolecular visible-lightphotoredox atom-transfer radical [3+2] cyclization of2-(iodomethyl)cyclopropane-1,1-dicarboxylate with alkenes and alkynes; visible lightphotoredox atom transfer Ueno-Stork reaction, a stereo-selective “Heck-type”reaction and a visible-light-mediated free radical [4+2] cycloaddition reaction ofdimethyl aniline to maleimide derivatives. These new reactions are good additions tothe field of visible-light photoredox chemistry.This thesis is divided into five parts:Chapter1: A simple metal-free catalytic sulfoxidation under visible light and air.A metal-free aerobic selective sulfoxidation photosensitized by Rose Bengal orsolid-supported Rose Bengal has been developed. The reaction utilizes visible light asthe driving force and molecular oxygen as the oxidant. The method is practical for itshigh efficiency and selectivity, extremely simple workup procedure, and minimalwaste generation.Chapter2: An intermolecular visible-light photoredox [3+2] ATRC reaction wasdeveloped. In this reaction, cyclopentane/cyclopentene derivatives were formed fromtwo structurally simple molecules through the construction of two new C-C bonds. Inour study, it was found that the homoallylic malonate radical was reactive towards electron-rich alkenes. But the reactions with unactivated alkenes were sluggish.Zn(OAc)2was found to enhance the reactivity of the radical intermidiate. The use ofLewis acid expanded the scope of the alkene substrates of the reaction. Comparedwith existing methods, the procedure is operationally simpler and does not involve theuse of stoichiometric hazardous radical initiators.Chapter3: A visible light-promoted atom transfer Ueno–Stork reaction wasdeveloped using Ir(ppy)2(dtb-bpy)PF6as the sensitizer.2-Iodoethyl propargyl ethersor2-iodoethyl allyl ethers were used as the radical precursors to constructtetrahydrofuran-containing fused [6,5] and [5,5] bicyclic frameworks.Chapter4: We developed a Heck-type reaction under visible light irraditon. Inthe absent of photosensitizer, only the thermodynamically more stable E-olefin wasformed as the only product. With photosensitizer the reaction generates Z-olefin asthe major product.Chapter5: Visible-light-mediated free radical addition reaction of dimethylaniline to maleimide derivatives.-Amino alkyl radical, an electronic-rich radical,showed high reactivity toward electron-deficient double bond of maleimids. Followedby free radical addition to benzene ring, quinoline derivatives was formed efficiently.