Metal-Free Coupling And Migration Reactions Of Diazoflavanones

This thesis consists of three parts.The first part is a literature review.It presents classical reactions of diazo compounds under thermocatalytic and photocatalytic conditions,such as insertion reactions,Wolff rearrangements,cycloadditions,Aldol reactions,etc.The Coupling reactions of diazo compounds,as well as 1,2 migration reactions,are highlighted.The Diels-Alder reaction involving enone and its application in the synthesis of natural products are also presented.The second part describes our development of a blue-light initiated coupling reaction of diazoflavanones and our attempt to use this reaction in the synthesis of the natural product Chamaejasmine.At the beginning,we explored the coupling reaction of diazoflavanones under light and explored methods for reducing the C-C double bond in the coupling product[3,3’-bichromanylidene]-4,4’-dione;we then attempted to capture the intermediate of the reaction and proposed a mechanism for the light-initiated diazoflavanone coupling reaction.Although it was not used in the synthesis of Chamaejasmine ultimately,we have developed a new method for the construction of sp~2C-C bonds and the synthesis of[3,3’-bichromanylidene]-4,4’-dione compounds.The third part describes our development of a method for the acid-catalyzed 1,2migration reaction of diazo-flavanones to prepare chromones.We used cheap and environmentally friendly hydrochloric acid instead of the classical noble metal catalysts.It provided very high yields and selectivity,offering a new method for the synthesis of chromones from flavanones.We next derivatized the resulting chromones to prepare[4.4.2]flavanone propellane via the Diels-Alder reaction and explored a one-pot method for the preparation of flavanone propellane from diazo-flavanones to flavanone propellane.