Studies On The Ring-Opening Reaction Of 3-aminocyclobutenones

Cyclobutenone is a class of four-membered small ring compounds with unique structure.These compounds are not only extremely important intermediates in organic synthesis,but also important structural units in natural compounds.Due to their unique α,β-unsaturated four-membered cyclic ketone structure with high ring strain,cyclobutenones are easy to open the ring under the conditions of thermolysis,photolysis and transition metal catalysis,resulting in highly reactive unsaturated intermediates,which was captured by nucleophiles,dienophiles and unsaturated bonds to perform a series of wonderful transformations.Therefore,the synthesis and application of cyclobutenones has been a hot topic in organic chemistry.In this field,various ring-opening reactions of various functionalized cyclobutenones have been widely reported,but reports on ring-opening reactions of aminocyclobutenones are rare.By analyzing the structure of the aminocyclobutenones,it can be known that the C=C bond of the compound has greater polarity due to the strong electron donating property of the amino group and the electron withdrawing property of the carbonyl group,which makes aminocyclobutenones have higher reactivities and could be a kind of more important organic synthesis intermediates.Therefore,exploring the ring-opening reaction of aminocyclobutenones is highly desired in organic synthesis.In this paper,using 3-aminocyclobutenones as starting materials and the exploration of ring-opening reactions of 3-aminocyclobutenones as the core,the cyclization reactions of 3-aminocyclobutenones with electron-deficient alkynes or amines were studied.The main contents are as follows:1.A novel[4+2]cycloaddition of cyclobutenones with electron-deficient alkynes has been developed under the condition of heating for the first time.The reaction can be performed in a highly regioselective manner and provide a straightforward and efficient method for the synthesis of 4-pyridone derivatives from readily available starting materials without transition metals in a single step.These results enrich the types of cycloaddition reactions between cyclobutenone and alkyne compounds and expand the further application of 3-aminocyclobutenones in the field of organic synthesis.2.A novel Cu(OAc)2·H2O catalyzed cascade cyclization reaction of cyclobutenones with electron-deficient internal alkynes has been developed for the first time.This reaction provides a new and highly efficient method for the synthesis of fully substituted indoles by formation of four new bonds and two rings from readily available acyclic starting materials in a single step.3.Using 3-aminocyclobutenones as the starting materials and Cu(OAc)2·H2O as the catalyst,the[4+1]cyclization of 3-aminocyclobutenones and amine compounds was successfully achieved and a series of multi-substituted 5-hydroxy-α,β-unsaturated-γ-lactam compounds were prepared.This method not only has the advantages,such as wide range of substrates,high tolerance of functional groups,mild reaction conditions,and simple operation,but also develops a simple and effective method for the synthesis of 5-hydroxy-α,β-unsaturated-γ-lactam compounds.