Studies On The Total Synthesis Of Taiwaniaquinoids And The Methodologies Based On 1, 3-Dithiane

This thesis main focused on the total syntheses of diterpenoids(±)-taiwaniaquinol B and(±)-dichroanone.An efficient Friedel-Crafts(FC)reaction has been developed for the synthesis of 4a-methyltetrahydrofluorene skeleton.Meanwhile,synthesis of cyclopropanes with 1,3-dithiane and carbolithiation of unactivated alkenes with dithianyllithiums are also studied.It consisted of the following four parts:Chapter1.Reaction of 1,3-dithiane with epoxide and the applications in natural products syntheses(review)Some general example of reaction of 1,3-dithiane with epoxides and applications in syntheses were reviewed,meanwhile,several applications in natural products syntheses also were discussed and the works of our group were introduced briefly.Chapter2.Total syntheses of diterpenoids(±)-taiwaniaquinol B and(±)-dichroanoneThe definition,classification of aromatic 6-5-6 tricyclic diterpenoid comounds,and previous synthetic reports of them were introduced briefly.There were three different routes leading to the total synthesis Taiwaniaquinoids.An efficient acid promoted domino Friedel-Crafts(FC)reaction has been developed for the total syntheses of diterpenoids(±)-taiwaniaquinol B and(±)-dichroanone,which could be generally used for the synthesis of 4a-methyltetrahydrofluorene.Chapter3.Synthesis of cyclopropanes by MIRC reactions of dithianyllithiumsThe MIRC reactions were introduced and previous synthetic reports of them for synthesis of cyclopropanes were introduced in brief.We have developed a new and high stereoselective process for synthesis of cyclopropanation derivatives when the monocarboxylic vinyl epoxide analogues reacted with dithianyllithiums.The monocarboxylic vinyl epoxide analogues were applied into the MIRC reactions.Chapter4.Carbolithiation of unactivated alkenes with dithianyllithiumsThe carbolithiation reactions of unactivated alkenes and the application of enantioselective synthesis were reviewed in briefly.Carbolithiation of a range of unactivated alkenes with dithianyllithiums is described,leading to the rapid,efficient and stereocontrolled assembly of highly functionalized dithiane intermediates for acyl-equivalents synthesis.