Studies On The Baylis-Hillman Reaction Of α-Formyl Ketene Dithioacetals With α-Aminocarbonyl Ketene Dithioacetals And Applications

The carbon-carbon bond formation is one of most functional reactions in organic chemistry.The Baylis-Hillman reaction(BH),the coupling of activated alkenes with carbon electrophiles under relatively mild conditions,is emerging as a valuable carbon-carbon bond forming reaction due to its' atom economical and producing useful functionalized molecules. As an essential component of the Baylis-Hillman,alkenes especially activated alkenes are a kind of very important building blocks in organic synthesis,and have been applied in various fields.While the alkenes which bearβ-substituent(s) especially with electron-donatingβ,β'-substituents could have some special characters due to the effect of electron-donating groups,and could be more important organic synthetic intermediate.In contrast to the extensive studies on the common activated alkenes,the investigations on the activated alkenes with electron-donating substituents remained poorly explored.So it is very necessary to study the characters and extend applications of this kind of alkenes with electron-donating substituents.α-Oxoketene dithioacetals are a kind of versatile intermediates used in organic synthesis during the past decades.It is clear that the highly polarized push(RS)-pull(RCO) interaction on the C-C double bond of these,β,β-dialkylthio-α,β-enones and analogues makes theirα-carbon atom a potential nucleophilic centre.Accordingly,theα-functionalization reaction ofα-Oxoketene dithioacetals has been developed in our group very recently.Some heteroatom functional groups such as Br,I and NO₂ have been successfully introduced into theα-position via halodecarboxylation or similar reaction.Recently,utilizing the electron richα-carbon atom ofα-EWG ketene-S,S-acetals(EWG:electron-withdrawing group),we successfully developed a novel Baylis-Hillman reactions of betweenα-EWG ketene-S,S-acetals with aldehydes and ketones.Based on the above results together with the fact that a series ofα-formyl ketene dithioacetals products were produced by the Vilsmeier reaction ofα-EWG ketene-S,S-acetals with Vilsmeier reagent(POCl₃-DMF),we paid our attention to the the Baylis-Hillman reaction ofα-formyl ketene dithioacetals withα-aminocarbonyl ketene dithioacetals in the presence of Lewis acids.On the basis of this B-H reaction,the nitrogen atom ofα-aminocarbonyl ketene dithioacetals attacks the carbon atom bonded to the alkylthio group and then undergoes an intramolecular addition-elimination reaction to furnish a series of nitrogen compounds.The following statements are the brief of my work.First,a series ofα-formyl ketene dithioacetals products were produced by the Vilsmeier reaction ofα-EWG ketene-S,S-acetals(EWG:electron-withdrawing group) with Vilsmeier reagent(POCl₃-DMF).Second,in the presence of Lewis acids,a series of 2-hydroxypyridine compounds were obtained by a sequential Baylis-Hillman and intramolecular annulation reaction ofα-formyl ketene dithioacetals withα-aminocarbonyl ketene dithioacetals under mild conditions.