Studies On Synthesis Of Carbazole Dericatives Via The Tandem Reaction Of Isocyanides

Carbazole derivatives are s series of important nitrogen containing heterocycles that are widely distributed in creature bodies and broadly applicated in aeras like chemistry,materials and medicine.It attracts lots of attention to develop highly efficient synthetic methods based on classical strategies.Isocyanides perform special properties due to the C(II)atom in the isocyano group.Isocyanides are applicated as important synthons in various types of reactions especially in the synthesis of nitrogen containing heterocycles.However there are few strategies of carbazole syhthesis reported via isocyanides.This thesis is about the carbazole synthesis through tandom reactions by isocyanides to develop simple and efficient synthetic methods.This thesis contains four chapters.In the first chapter,there is a summery of the applications and synthetic methods of carbazoles.Besides,the the general properties and important reactions of isocyanide are introduced.In the second chapter,tandom [4+1]/[4+2] annulations of o-alkenyl arylisocyanides with ?,?-unsaturated carbonyl compounds are introduced as a domino access to carbazole derivatives.To our acknowledgement,it is the first strategy to take o-alkenyl arylisocyanides in use for carbazole synthesis.This simple efficient strategy is environmentally friendly and has a broad substrate scope and high atom economy with water as the only by-product.Intermediates are obtained through control experiments to shed light on the reaction mechanism of this domino reaction.First,nucleophilic attack of isocyanides onto ?,?-unsaturated carbonyl compounds affords aminofuran intermediates via a [4+1] cycloaddition.Next,a furan-based [4+2] intramolecular Diels-Alder reaction occurs to construct the new five-member and six-member rings,which is followed by subsequent C-O scission,1,3-proton shift and elimination of water to give the final products.In the third chaper,multicomponet reactions of aldehydes,o-alkenyl arylisocyanides and 5,5-dimethyl-1,3-cyclohexanedione are introduced as an efficient method to form carbazole derivatives.5,5-dimethyl-1,3-cyclohexanedione is taken advantage of its high reactivity towards aldehydes in this method to perform reactions.A Knoevenagel condesation takes place at first to form ?,?-unsaturated intermediates.Then tandom [4+1]/[4+2] annulations occurs between o-alkenyl arylisocyanides and the intermediates to give carbazole derivatives.Some other compounds containing the structure of ?-dicarbonyls are also examed and corresponding products are obtained in moderate to excellent yields.Moreover,this method is expanded into biscarbazole and tricarbazole synthesis.In the fourth chapter,synthetic routes to indolocarbazole alkaloids Arcyriaflavin A,Racemosin B and Malasseziazole C are designed according to the structure of o-alkenyl arylisocyanides and the characteristics of the tandom [4+1]/[4+2] annulations.And these alkaloids are synthesized successfully and afforded in yields similar to literatures.