Study On Phosphine-catalyzed [3+2] Annulation Reaction Of Electron-deficient Conjugated Enynes With Allenoates And Selective Transformations Of The Products

Cyclopentenes are rich-found in a wide range of natural products and drugs as building blocks in organic synthesis. Many chemists have focused their research interests on their synthesis and transformation of this kind of compounds. How to efficiently establish highly substituent cyclopentenes with multi-functional groups remains a continuing challenge in synthetic commonity. phosphine-catalyzed [3+2] annulation reaction is proved to be an efficient approach to cyclopentenes.In recent years, phosphine catalytic [3+2] cycloaddition have been widely studies. However, there is no report on the [3+2] cycloaddition of conjugated enynes with allenoates. Meanwhile, highly substituted furans can be found as core structure in many natural products, commercially important pharmaceutical, food taste enhancers, bioregulators and dynes. It is also considered as a kind of building blocks for the construction of numerous cyclic and acyclic compounds. In this thesis, we have focused on the synthesis of highly substituted cyclopentenes by the annulation reaction of conjugated enynes with allenoates and selective transformations to furan under the catalysis of gold complex. The thesis includs two parts as following:Part I:The highly selective [3+2] cycloaddition of conjugated enynes with allenoatesUnder the catalysis of triphenylphosphine, the reaction of (E)-3-benzylidene-5-phenylpent-4-yn-2-one with allenoates can give highly functionalized cyclopentenes with high selectivities. In which only the double bond of enynes is participated as the two-carbon component.Partâ…¡:The selective transformation of highly functionalized cyclopentenesUnder the catalysis of gold(I) complex, highly functionalized cyclopentenes can convert into 5,6-fused bicyclic compound via selective 1,2-alkyl migration, For those styryl-substituted substrates, there are two different migration pathway, one is to form 2,3-fused bicyclic 2,3-dihydro furan, the other is to form 3,4-fused bicyclic furans. The selectivity depends on the structure of the substituents and the counter anion.