The Synthetic Applications Of Alkylthio Activated Alkenes

The carbon-carbon bond formation is one of most functional reactions in organicchemistry. The Baylis-Hillman reaction (BH), the coupling of activated alkenes with carbonelectrophiles under relatively mild conditions, is emerging as a valuable carbon-carbon bondforming reaction due to its' atom economical and producing useful functionalized molecules.As an essential component of the Baylis-Hillman, alkenes especially activated alkenes are akind of very important building blocks in organic synthesis, and have been applied in variousfields. While the alkenes which bear β-substituent(s) especially with electron-donatingβ, β'-substituents could have some special characters due to the effect of electron-donatinggroups, and could be more important organic synthetic intermediate. In contrast to theextensive studies on the common activated alkenes, the investigations on the activated alkeneswith electron-donating substituents remained poorly explored. So it is very necessary to studythe characters and extend applications of this kind of alkenes with electron-donatingsubstituents.α-Οxoketene dithioacetals are a kind of versatile intermediates used in organic synthesis,in our recent research on the synthesis and applications of α-EWG ketene-S,S-acetals, a seriesof alkenes with electron-donating alkylthio groups at its' β-position were obtained. studyingthe property and synthetic application of this kind of substited alkene has become mainpurpose in our present work. The coupling reactions of alkylthio activated alkenes witharylaldehydes, the Michael addition reactions of alkylthio activated alkenes withα, β-unsaturated carbonyl compounds and addition-elimination reaction of alkylthio activatedalkenes with aliphatic or aryl acylchlorides were investigated and the experimental results arelisted as followed.In the presence of TiCl4, the coupling reactions of alkylthio activated alkyl vinyl ketoneswith aryladehydes were first performed and a series of the polyfunctionalized 1,4-pentadienescompounds were obtained, afterward, the Claisen rearrangements reactions of thesecompounds catalyzed by base were completed and generated the correspondingpolysubstituted cyclohexenone compounds. The experiment revealed that the reactionsproceed in a highly chemoselective and atom economical manner, and the products areimportant intermediates in organic synthesis.Similar to the reaction condition presented, the double Baylis-Hillman reactions ofalkylthio activated acrylonitrile with aryladehydes were carried out and the range of thisalkylthio activated alkenes was extended, at the same time when researching the property ofalkylthio activated alkenes, a efficient and practical route to synthesize alkylthio activatedacrylonitrile was found, which could handy be generated via deacetylation and dehydrationreaction, and the starting materials are readily available.Owing to electrophilic nature of α-carbon on α-οxoketene dithioacetals, the Michaeladdition reactions of alkylthio activated alkenes with α, β?unsaturated carbonyl compoundswere performed, the tropism of the reaction depends on not only type of activated alkene butalso the activities of α, β-unsaturated carbonyl compounds, the results infirmed the diversityof different kinds of activated alkenes, it presents evidence for the selection and application ofdifferent activated alkeneThe α-functionalized ketenedithioacetals, α-acetyl-α-acyl-ketenedithioacetals wereperformed in mordate to high yields under mild reaction conditions via acylation reaction ofα-acetyl ketenedithioacetals and aliphatic or aryl acylchlorides. These experimental resultsfurther confirmed the electrophilic nature of α-carbon on α-οxoketene dithioacetals, whichpresented a new idea to apply the α-position of α-οxoketene dithioacetals in organicsynthesis.