Synthesis Of Olefin Sulfones Involving Sulfonyl Radicals

In this thesis,a series of C-S bond coupling reactions involving sulfonyl radical were studied.The results are as follows:1.Copper-catalyzed coupling reaction of dehydrogenative alkyl arenes with sulfonyl radicalIn this chapter,synthesis of unsaturated vinyl sulfones via cross-coupling of sulfonyl radical generated from N-sulfonyl benzimidazole with dehydrogenative simple alkyl arenes under copper catalysis was studied.The directly cross coupling of N-sulfonyl benzimidazole and ethylbenzene was chosen as a model reaction in the presence of copper trifluoromethanesulfonate toluene complex to give the corresponding vinyl sulfone derivatives in up to 75% yield(Figure 1).Under the optimized reaction conditions,the scope of the substrates was examined.Alkyl arenes with electron-withdrawing and electron-deficient functional groups as well as alkyl heterocycles reacted smoothly with N-sulfonyl benzimidazole to give vinyl sulfone derivatives in good yields.Vinyl sulfone derivatives were also obtained from the reaction of ehtylbenzene with N-sulfonyl benzimidazole bearing electron-withdrawing and electron-donating groups on phenyl as well as heterocycles,three-membered ring and aliphatic group on N-sulfonyl benzimidazole.The mechanism of the reaction was considered to proceed through a single-electron-transfer pathway which initiated by the addition of sulfonyl radical to the in-situ generated styrene and subsequent ?-hydrogen elimination.The structure of3 ba was determined by X-ray diffraction.The mechanism of the transformation was proposed and investigated by controlled experiment.(Figure 3).2.Coupling reaction of sulfonyl radical with allylbenzene under metal free conditionsIn this chapter,a series of allyl sulfone compounds were synthesied by the allylicsulfonylation reaction of allyl benzene under metal-free conditions.Sulfonyliodide and allyl benzene were chosen as model substrates to perform the reaction.In the presence of the base in DME(ethylene glycol dimethyl ether),the reaction proceeded smoothly at 80 oC under Argon to give out allyl sulfone derivatives in moderate yield.The plausible reaction mechanism is proposed as follow(Figure 5): sulfonyl radical and iodide radical were generated by the cleavage of S-I bond under heating conditions.Subquently,radical addition of sulfonyl radical and iodide radical with allyl benzene furnish the intermediate B.Under basic conditions,?-H elimination of intermediate B produced intermediates C and product D.Intermediate C can be isomerised to product D under heating condition.