| Olefins and alkynes are very important chemical raw materials.Not only are they the starting materials of many chemicals,but the most important C2 linkers in organic synthesis.They are capable of undergoing electrophilic addition,nucleophilic addition,oxidation,reduction,halogenation,polymerization and other reactions.Unsaturated carbon-carbon bonds can serve as bridges to effectively connect various functional groups through these elegant reactions,which rapidly increase molecular complexity in a convenient way.Owning to the fact that the C-S bond is ubiquitous in many pharmaceutical molecules and natural products,the introduction of S-containing functional groups into carbon-carbon unsaturated bonds through green and sustainable methods has attracted wide attention of chemists.In this paper,we demonstrated the photocatalytic strategies to fulfil the C-O and C-S difunctionalization of styrene and its derivatives.Besides,regio-and stereoselective hydrosulfonylation of electron-deficient alkynes to access both E-and Z-sulfonylated ?,?-unsaturated carbonyl compounds catalyzed by Br?nsted acid have been introduced.Two simple and efficient methods were provided for the rapid construction of C-S bonds.In the second chapter,we concentrated on the synthesis of ?-thiocyanato alcohol with organic dye rose bengal(RB)as photosensitizer,?-methylstyrene and ammonium thiocyanate as substrates under visible light irradiation.After screening photosensitizers,the amount of photosensitizers,solvents,light sources,additives,gas atmosphere and thiocyanate salts etc.,finally the optimal reaction conditions were established.Subsequently,the scope of substrates was explored and 21 compounds of ?-thiocyanato alcohols were obtained with the yield up to 76%.Through a series of control experiments,we presumed that the reaction process involves free radical intermediates.Furthermore,when we conducted the radical inhibition experiment with radical scavenger 2,6-di-tert-butyl-4-methylphenol(BHT),the separated derivative of BHT proved that peroxide radical was the key intermediate of this reaction.Employing this methodology,C-S and C-O bonds could be efficiently constructed in one-pot reactions.Moreover,there was a vital enhancement for the analogical reactions requiring the utility of an external reducing agent so as to reduce the peroxide intermediate into the corresponding alcohol.During this mild and green photocatalytic protocol,dioxygen not only acted as an excellent terminal oxidant,but also a green source of oxygen.The activation of dioxygen by photoredox catalysis provided an environmental-friendly tactic for the synthesis of O-containing compounds.In the third chapter,we mainly focused on the preparation of E-and Z-?-sulfonylated ?,?-unsaturated carbonyl compounds utilizing sodium sulfite and sulfinic acid as sulfonyl sources in the presence of Br?nsted acid.The optimum reaction conditions of E-selection and Z-selection were determined by screening a wide range of solvents,acids,bases and buffers.The substrate scopes were investigated and 27 E-selective products and 21 Z-selective products were obtained.All of these reactions possessed good yield and excellent stereoselectivity.Through a series of control experiments,including configuration conversion experiments and kinetic series experiments,we proposed a plausible reaction mechanism for this reaction: thermodynamically stable E-isomers provided by hydroxylallyl intermediates or Z-isomers furnished by a synergistic three-component electrophilic addition mechanism.This sulfonylation reaction was easy to be scaled up to a gram scale while the yield and selectivity were almost unaffected.Morever,the potential application of this methodology and the different properties of E and Z isomers have been explored. |
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