α-EWG Ketenedithioacetal As Carbon Nucleophile In The Application Of Synthetic Organic Chemistry

The carbon-carbon bond formation and the functional group transformations are most fundamental reactions for the construction of a molecular framework and hence represent a forefront of research in organic chemistry. The Baylis-Hillman (BH) reaction, the coupling of activated alkenes with carbon electrophiles under relatively mild conditions, is emerging as one of the most valuable carbon-carbon bond forming reaction in recent years. Since the BH reaction possesses the two most requirements, atom economy and generation of useful functional groups,it qualifies to be the list of efficient synthetic reactions. The BH reaction is the coupling reaction of different electrophiles and theα-position of activated alkenes under mild conditions. This reaction possesses three components: activated alkenes, electrophiles and catalyst which produces fused functional groups molecular. As an essential component of the BH reaction, 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'-disubstituents could have some special characters due to the effect of electron-donating groups (EDGs) and electron-withdrawing groups (EWGs). In contrast to the extensive studies on the common activated alkenes, the investigations on the electron-donating activated alkenes remained few researches. So, it seems to be very important to deeply study the characters and extend applications of this kind of alkenes with EDGs.α-Οxoketene dithioacetals are a kind of versatile intermediates used in organic synthesis during the past decades. It is a type of activated alkenes, which bear double donating alkylthio groups atβ?position. Our recent work focused on the property and synthetic application of this kind of activated alkene. In connection with the characteristic of BH reaction and the importance of carbon-carbon bond formation, we will investigate the three components reaction of alkylthio groups activated alkenes, different aldehydes and nitriles; the BH reaction of pyridine aldehyde and alkylthio groups activated alkenes including the application of the adducts; the carbon-carbon bond coupling reaction of alcohols and polarized ketene dithioacetals. The following statements are the brief of my work. Mediated with titanium (IV) chloride (TiCl4), a series of Aza-Baylis-Hillman reaction adducts were obtained vir three components reaction of bisalkylthio activated polarized alkene, different arylaldehyde and nitrile. This type of reaction is a sequence of Baylis-Hillman reaction and the active adducts was then conformed a Ritter fashion reaction. This reaction covers the mild reaction condition, high yield and the products bearing fused functional groups, etc.When furfural or thiophene-2-carbaldehyde was taken as electrophile, the similar BH type reaction could not give the Aza-BH reaction products. The active alcohol was first produced, and a more stable carbocation was formed after an abnormal rearrangement by the catalyst, which was captured by the activated alkene.The BH reaction of alkylthio activated activated alkenes and picolinaldehyde was realized. The experimental results illuminate that the pyridine can cooperate with titanium and deactivated the corresponding adducts which could not react with activated alkene or nitriles any more. When the BH adducts is derived from the reaction ofα?CN-β,β?bisethylthioketene acetal and picolinaldehyde, it can be converted into potential biological and medicinal active indolizine derivatives after intramolecular themal cyclization reaction. More important, the obtained ethylthio activated indolizine is a type of highly activated carbon nucleophiles. It can be reacted with aldehydes or ketones under very mild conditions to afford a series of triaryl compounds containing indolizine nucleus.The coupling reaction of a series ofα-EWG ketene dithioacetals and alcohols was carried out base on the strong nucleophilicα-position of the tested ketene dithioacetals. The experimental results prove that the reaction can catalyze by either Lewis acid or protonic acid and show high nucleophilic abilities of theα?position of these polarized alkenes.