Synthesis Of Heterocyclic Compounds From Aryltriazene

Heterocyclic chemistry is an important composing part of organic chemistry. In view of the particularly interesting properties and wide applications of heterocyclic compounds in medicine, pesticides, dyes, biological membrane materials, superconducting materials, molecular devices and storage materials, new practical synthetic methods for the construction of heterocyclic compounds are highly desired. Aryl triazenes (R-N=N-NR’R"), as useful building blocks for the construction of new organic heterocycles, have been studied extensively. An attractive feature of aryl triazenes is all bonds (R-N, N=N, and N-N) of the triazene functionality can be broken selectively that may lead to the formation of a variety of different heterocycle products. Thus, it is accessible but challenging to control the regio-and stereoselectivity of the triazene chenistry to form functionalized heterocyclic compounds. In this dissertation, we summarized the reactions related to the triazene and described the new reactions and methods for constructing carbazoles, dibenzofurans, indazoles, dihydrofuro-quinolines and4-quinolones. The main contents are as follows.1. Lewis Acid-Promoted Intramolecular Aromatic Substitution for the Synthesis of Carbazoles and Dibenzofurans from Biaryl TriazenesWe discovered a BF3?OEt2-promoted nucleophilic aromatic substitution approach to the synthesis of highly substituted carbazoles and dibenzofurans from biaryl triazenes. The annulation process was applied to the total synthesis of carbazole alkaloids:Clausine C, Clausine R and Clauraila A.2. Bi(OTf)3or DBSA Catalyzed Intramolecular Cyclization of Triazenylaryl Allylic Alcohols for he Synthesis of trans-3-Alkenyl IndazolesAn efficient Bi(OTf)3catalyzed synthesis of3-alkenyl-2-pyrrolidine-2H-indazoles in CH2Cl2from triazenylaryl allylic alcohols is reported. The reaction has a good functional groups tolerance. Then an alternative but more economical and environmentally friendly reaction system was achieved. When using dodecyl benzene sulphonic acid (DBSA) as the catalyst, the reaction can be carried out in water. Furthermore, upon cleavage pyrrolidine from trans-3-alkenyl-2-pyrrolidine-2H-indazoles with Zn in CH3COOH, trans-3-alkenyl-1H-indazoles were obtained in good to excellent yields.3. Synthesis of Dihydrofuro-quinolines and4-Quinolones Starting from Triazene-cyclopropyl KetonesThe reaction of triazene-cyclopropyl ketones with NaN3in the presence of BF3?OEt2/TFA gave azido-cyclopropyl ketones. And then we developed the Ru-catalyzed synthesis of dihydrofuro-quinolines from azido-cyclopropyl ketones via the reduction-cyclization-rearrangement process. When the reaction was carried out under H2(1atm) in the presence of Pd/C, the4-quinolones were obtained in excellent yields.