The Concise And Efficient Total Synthesis Of Taiwaniaquinones

In this thesis, Taiwaniaquinol B, 5-epi-taiwaniaquinone G and an isomer were synthesized through a novel and efficient method under the present research situation of Taiwaniaquinones. The mechanism of carbocation rearrangement reaction process was explored and further verified. So that the synthesis other natural products could make the rearrangement mechanism of dearomatic and aromatic process as reference.Nazarov cyclization is an effective method for the synthesis of cyclopentenones which is widely used in constructing natural products. The Nazarov cyclization reaction work through 4π—Electron conrotatory ring closure of bisving ketones under acidic condition to generate cyclopentanones. Cyclopentanone motifs were widespread in natural products and many biologically active compounds, so this reaction was often used in the synthesis of natural products for the construction of five-membered ring.In this thesis, to synthesize 5-epi-taiwaniaquinone G, the [6,5,6]-tricyclic abietane skeleton of the Taiwaniaquinones family was built through a tandem acylation-Nazarov cyclization reaction in the presence of trifluoroacetic anhydride and Lewis acid catalyst. This strategy simplified the synthetic route and improved the yield is economical, practical, atom efficient and environment-friendly. The isopropyl group was introduced in high yield on the steric hindrance site using the pechmann condensation which was the key reaction to synthesize coumarin followed by reductive hydrolysis. This method in organic synthesis can be used as a valid reference for the introduction of an isopropyl group ortho to the phenolic hydroly group. In the presence of 3,5-dimethyl pyrazole, the methene group of the five-membered ring of the [6,5,6]-tricycle was selectively oxidized with chromium trioxide to produce the cyclopentenone function. This method was highly selective, and played a key role in the synthesis of Taiwaniaquinol B.