Studies On Sulfurations And Redox Reactions Of Enynes Based On Potassium Xanthate

Potassium xanthate is a class of inexpensive and novel organic compounds in organic synthesis.Compared with other sulfur-containing compounds,potassium xanthate can be used not only for free radical reaction but also as a direct“sulfur source”for the construction of sulfur-containing compounds.Since sulfur-containing heterocyclic compounds have a wide range of biological activities in natural products and drugs,develop a simple and efficient methods for use of potassium xanthate as a"sulfur source"to construct new reactions,which have an important application value.Our aim is to synthesize various functional molecules,such as thiophene,thiopyran,olefin,and etc.,which was obtained by using alkynes or olefin as raw materials and the formation of C-S and C?sp²?-C?sp²?atomic bonds through the promotion of potassium xanthate.There will be presented in the following five chapters.?1?Copper catalyzed 2-fluoroarylalkynol and potassium xanthate via thiolation and oxidation cascade to produce 2-carbonylthienopyridine compounds.Broad substrate scope,and good functional group tolerance were prominent features of this transformation.Simultaneously,we have demonstrated that it's possible reaction mechanism for the synthesis of 2-carbonylthienopyridine,initially,the nucleophilic substitution reaction of potassium xanthate occurs at the ortho C-F position of 2-fluoroarylalkynol to obtains a thiol-containing aryl alkynol intermediate.Next,intermediate may undergo a thioester cleavage and5-endo-dig cyclization to synthesis 2-carbonylthienopyridines under copper-catalyzed condition.?2??Z?-tetrahydrothiophene derivatives was synthesized through radical-mediated cyclization from EtOCS₂K and alkynyl halide.which was obtained by nucleophilic thiyl radical intramolecular cycloaddition cascade process under transition metal-free and oxidant-free conditions.Simultaneously,our method also has some advantages,such as,a broad substrate scope,excellent stereoselectivity,and used stable and inexpensive EtOCS₂K as the“sulfur source”and etc.?3?The four chapter of this article have introduced a novel method for the selective semi-reduction of internal alkynes to obtain trans-olefin.which was used inexpensive potassium xanthate as a reducing agent and water as hydrogen donor.In this reaction,a wide range of substrates were well compatible,such as,aryl alkyne,alkyne and terminal alkynes.Possible reaction mechanism like that,Initially,an electrophilic addition occurs at the alkyne with potassium xanthate to generate an intermediate of vinyl thioester.Next,followed by a second addition to obtain an intermediate of ethyl thioester.Then,a thioether was obtained by electron transfer,Finally,trans-olefin products were synthesized via configuration flipping and under thermodynamic control.?4?The five chapter of this article have discovered a free radical type of reaction to synthesis of?-ketoesters based on potassium ethyl xanthate.First,the reaction may be produces 2-iodo-1-phenylethanone from acetophenone and iodine,which was oxidized to produce aldehyde ketone compounds depended on dimethyl sulfoxide.Next,potassium ethyl xanthate reacts with iodine together provide an ethyl oxygen free radical to synthesis?-ketoesters.?5?The six chapter of this article have developled a potassium xanthate promoted the isomerization of cis-olefins and D2O participated in D/H exchange to synthesis deuterated trans-olefins.The methodology was highly practical and it provides a straightforward approach to a serirs of deuterated trans-olefins.Firstly,the reaction promotes the cis-olefin to obtain a cyclic thiother compound by EtOCS₂K,and releases carbon disulfide,etc.,and then undergoes thermodynamically controlled breaking of the C-S bond and deuteration of D2O to obtain deuterated trans-olefins.