Studies On The Cycloaddition Reactions Of Using Electron-deficient Allenes

The chemistry of allenes has experienced a great expansion over the last decades.The higher reactivity of this type of cumulated systems compared to that of simple alkenes,together with their intrinsic complexity generating characteristics and the possibility for further manipulating the double bond remaining in the resulting cycloadducts,offers a number of unique opportunities for the development of novel regioselective and stereoselective synthesis of cyclics and building blocks.In this thesis,we focused our research on the studies of electron-deficient allenes containing a coordinating bidentate functional group to construct isoxazolidines and 1-azadienes through Lewis acid catalyzed[3+2]cycloadditon reaction and[2+2]cycloisomerization,respectively.The achieved results are briefly summarized as follows:The research on the Lewis acid-catalyzed[3+2]cycloaddition of sulphonyl allenes and nitrones was introduced in the second chapter.Under Lewis acid condition,isoxazolidines were obtained up to 72%yield.However,the aim to convert the isoxazolidines to the rearrangement product pyrrolidin-3-ones was failed.In the third chapter,the unprecedented intermolecular[2+2]cycloisomerization between allenyl imide and N-（2-methoxyphenyl）aldimine counterparts catalyzed by a Ni（ClO₄）₂·6H₂O Lewis acid at room temperature was discovered,providing a facile access to 1-azadiene derivatives with high atom economy.The incorporation of an 2-oxazolidinone group into allene amides resulted in unusual reactivity for the imine-metathesis and synthetic application to a chiralγ,δ-unsaturatedβ-ketoimide.Mechanistic experiment with density functional theory（DFT）computation rationalized the proposed catalytic pathway involving initial stepwise[2+2]cycloaddition,two-time proton transfer to form a 2-azetine intermediate,and final conrotatory ring opening for trans-1-azadiene based substance.