Rhodium-Catalyzed Tandem Cyclization Of Vinylic Oxiranes With Alkynes

The design and development of new tandem cyclization/cycloaddition reactions of readily available substrates in terms of minimization of synthetic steps together with maximization of target-relevant complexity offer tremendous opportunities to move syntheses towards the ideal. This thesis have developed a rhodium(Ⅰ)-catalyzed efficient, tandem cyclization of vinylic oxirane-alkyne substrates, providing a strategically novel, diastereoselective access to [3.1.0]bicyclic products and [5-7-5] tricyclic compounds, in which the vinylic oxirane is first explored to be as a heteroatom-containing five-atom component in cycloaddition reactions.1、The first Rh(NHC)-catalyzed tandem intramolecular hetero-[5+2] cycloaddition/Claisen rearrangement reaction of vinylic oxirane-alkyne substrates, which provides an atom-economic and diastereoselective access to tetrasubstituted vinylcyclopropanes (VCPs) has been developed (48-94%yield). The use of RhCl(IPr)(COD)/AgSbF6bearing strong a-donating IPr ligand is critical to avoiding the competing isomerization of the epoxide. Based on the isolation and characterization of hetero-[5+2] cycloadduct and control experiments, a mechanism was proposed. Complete chirality transfer in the present tandem process was also observed, providing a novel and rapid method for the synthesis of [3.1.0] bicycles in an enantioselective manner. The attempt has been made to total synthesis of the natural product-Aphanamol I by application of this methodology.2、A novel Rh(Ⅰ)-catalyzed diastereoselective tandem hetero-[5+2] cycloaddition/Claisen rearrangement/[5+2] cycloaddition reaction of vinylic oxirane-diyne substrates for the construction of the linearly fused5-7-5tricyclic systems in a step, atom and time economical fashion from readily available starting materials has been developed. Furthermore, the chemoselective and diasteroeselective functionalization of the5-7-5tricyclic products and scalability to gram-scale, well demonstrate the efficiency and synthetic potential of this tandem reaction.