Study On The Novel Cycloaddition Reaction Of Allenes

Seven-membered all carbon atom rings appear as a prevailing subunit in the core of biologically active natural products such as ingenol,englerins A,frondosin B,cortistatin A,and guanacastepene A.In the total syntheses of these compounds,the construction of seven-memebered rings always constitutes one of the major synthetic challenges due to both enthalpy and entropy issues.Consequently,the development of efficient methods for cycloheptane preparation continues to be an important organic chemical endeavor.However,due to the activation entropy of the reaction and the cross-ring tension existing in the reaction transition state,the synthesis of the seven-membered ring is challenging.（4+3）cycloadditions between aryloxyallenes and furans are described.The reaction features an in situ formation of oxygen-stabilized oxyallyl cations via epoxidations of alkoxyallenes in the presence of KH₂PO₄.Multi-oxygen-substituted cycloheptanes can be prepared by this method efficiently and diastereoselectively.