Study On The Synthesis Of Benzofurans From Ortho-Hydroxy Substituted Aromatic Ring

Benzofuran is a heterocyclic compound consisting of benzene and furan ring and is widely distributed in nature,which is the "parent" skeleton of many related compoundswith more complex structures.Benzofuran derivatives have attracted significant attention in the past years because of their various biological and pharmaceutical applications,such as anti-inflammatory,analgesic,anti-infective etc.Inaddition,substituted benzofurans find application such as of fluorescent sensor,antioxidants,brightening agents and in otherfield of chemistry and agriculture.The extensive pharmacological activities of benzofuran compounds show that the synthesis of aseries of compounds is of great significance.Therefore,the preparation of benzofurans has always been the focus of research.The ortho-alkynyl naphtholcan be easilyprepared,whose triple bonds can be activated by various catalysts and is one of the important starting materials for preparing heterocyclic compounds.Based on this research,we mainly studied the preparation of benzofuran from ortho-alkynyl naphthol and two different dipoles.The work of this paper is mainly divided into the following two parts:Part Ⅰ:We have developed a new synthesis of polycyclic benzofurans.A series of tricyclic furan compounds have been prepared using sulfur ylide and ortho-alkynyl naphthol as model substrates.Although there are many methods to construct benzofurans,nearly all of them need to add catalysts to promote the reaction,and there are few methods to construct benzofuran compounds without any additives.However,this reaction does not require any additives,which has high atom-economy and a wide range of substrate adaptation.Both sulfur ylide and ortho-alkynyl naphthol with different electronic properties can successfully participate in the reaction.In addition,tricyclic furan compounds can undergo a series of transformations to obtain polycyclic compounds with good yields,providing a new method for constructing complex polycyclic structures.Finally,we studied the reaction mechanism.The transforman proceeds through an isomerization/nucleophilic addition/cyclization/aromatization cascade.Part Ⅱ:We used vinylbenzoxazinanone to react with ortho-alkynyl naphthol to generate disubstituted naphthafurans.Through a series of screening of the reaction conditions,we found that the reaction can obtain disubstituted naphthafuran compounds with 89%yield at room temperature,using DCM as solvent and Pd₂（dba）₃/cinchonine as catalytic system.Although we did not get the expected axial chiral compounds,this reaction also provided a new method for preparing furan derivatives...