Studies On The Synthesis Of 2-Methyl-3-(2-Fluoro-3-Oxo-3-Phenylpropylene)-Indole And Its Cyclization:Synthesis Of Carbazole

Carbazole is an important class of nitrogen heterocyclic compounds that are widely used in drug discovery and material science because of their significant biological,chemical or physical properties.In view of this,studies on the efficient synthesis of carbazole have attracted particular attention,and the preparation of carbazole derivatives via cyclization of indole is an important route.The known methods can be divided into two broad categories,including the cyclization of C-2 or C-3 functionalized indole,and the 2-,3-position C of indole simultaneously participating in the ring formation reaction to construct carbazole.The method for synthesizing carbazole based on C-3 functionalized 2-methyl indole is extremely rare.In this paper,we first designed and synthesized 2-methyl-3-?2-fluoro-3-oxo-phenylprop yl?-indole by the ring opening reaction of 2-methylindole with difluorocyclopropane.TFAA would promote the formation of the carbazole derivative via cyclization under mild condition with high efficiency.The results of this work provide a new approach to the synthesis of carbazole.The main research contents are as follows:1.Review the research progress in the synthesis of carbazole based on indole derivatives.Including:C-3 functionalized indole to synthesize carbazole,C-2 functionalized indole to synthesize carbazole,from simple indole to synthesize carbazole and C-2,C-3 disubstituted indole to synthesize carbazole.2.This paper realized the intramolecular cyclization reaction of functionalized indole to carbazole under the promotion of TFAA.The experimental results and related literatures showed that the released trifluoroacetylium ion could be trapped by C-3 position of indole,which would provide the nucleophilic enamine species by deprotonation.The moiety of the?-fluoroketone reduces the energy of the aromatization so that the reaction can construct the benzene ring structure under mild conditions.The efficient synthesis of carbazole was achieved based on the above two points.3.25 carbazole compounds were synthesized and characterized by ¹H NMR,¹³C NMR,¹⁹F NMR and HRMS.