Methodology Research On The Tandemcyclizayion Of Diacetylene Dithiocyanates

Thiocyanate(RSCN)are important nitrogen-sulfur compounds containing thiocyanate functional groups.These compounds have good anti-inhibitory enzyme activity,anti-insecticidal activity,anti-microbial and anti-proliferative activity,and are widely used in medicine,natural products,and organic synthesis[73].Thiocyano group is a functional group with double reaction sites,which can be converted into mercaptans,thioethers,sulfur-containing heterocyclic compounds,disulfide compounds,phosphorothioate compounds,and has broad applications prospect in synthetic chemistry.There are mainly two traditional methods for constructing carbon-sulfur bonds:(1)Using a substrate to react with a thiocyanation reagent to synthesize thiocyanate,it mainly includes ~-SCN nucleophilic substitution reaction,~+SCN electrophilic substitution reaction,SCN radical reaction;(2)Synthesis of thiocyanate compound by cyanation reaction of organic sulfide,which mainly includes~-CN nucleophilic substitution reaction,~+CN electrophilic substitution reaction,and CN radical reaction.The methods of introducing thiocyano groups into aromatic compounds and olefins have been extensively studied,but there are few reports on the methods of introducing thiocyano groups into alkynes.Therefore,it is very necessary to introduce the thiocyanate group into the molecule by the method without metal catalyst.Based on the above research background,this article mainly discusses the cyclization reaction of 1,6-diacetylene and trimethylsilyl isothiocyanat at room temperature without metal participation afford 1,4-dithiocyanate conjugated dienyl compounds.In the 1,6-dithiocyanation tandem cyclization reaction,we screened oxidant,solvent,temperature,thiocyanate source,equivalent of thiocyanate source,and equivalent of oxidant respectively,determined the reaction conditions.After determining the optimal reaction conditions,this article carries out a series of developments on the substrates of the reaction.It can be found that when different substituents are attached to the benzene ring substrate heterocyclic substituted substrates can afford the target compound with a high separation yield.The ratio of E:Z varies from 2:1 to>20:1,a total of 18 dithiocyanate tandem cyclization products were obtained.According to experimental results,a possible reaction mechanism is proposed.First,iodobenzene acetate reacts with trimethylsilyl isothiocyanate to obtain dithiocyanato iodobenzene,further produces polymerized dithiocyanate compounds,which are split to produce two molecules of thiocyano radicals,which react with alkynyl groups.Radical addition produces alkenyl free radicals,the radicals undergo intramolecular cyclization reaction to obtain conjugated dienyl free radicals,which react with another molecule of thiocyano radicals to obtain cyclized dithiocyanate products.