Study On Three-Component Synthesis Of 1,2-Diarylindoles Under Transition-Metal-Free Conditions

Indole is a nitrogen-containing heterocycle with a central position in organic chemistry and is considered to be a privileged structure in medicinal chemistry.Furthermore,indole derivatives also serve as versatile precursors for the preparation of agricultural chemicals and functional materials.Therefore,it is not surprising that enormous efforts have been devoted to the development of efficient synthetic protocols for the preparation and direct functionalization of this heteroaromatic compound.As a subclass of indole derivatives,1,2-diarylindoles have a wide range of biological activities.For instance,1,2-bis(4-fluorophenyl)-1H-indole-5-carboxylic acid can inhibit the activity of PASK.Owing to the diverse significant biological properties of 1,2-diarylindoles,their synthesis has gained considerable interest.In this paper,we used cyclohexanones,α-hydroxy-ketones and anilines as raw materials and synthesized a series of 1,2-diarylindoles.The main contents are as follows:Developed a unique approach for the synthesis of various 1,2-diarylindoles from cyclohexanones,α-hydroxy-ketones and anilines under transition-metal-free conditions.Secondary amines acted as the efficient organic catalyst in this kind of transformation.Cyclohexanones were employed as the aryl sources under aerobic conditions without the aid of a transition-metal catalyst.The reaction showed good substrate scope and various functional groups were well tolerated under the optimized reaction conditions.Moreover,two bioactive molecule precursors were synthesized by this present method.This method showed the great advantages:(1)the required starting materials were readily available;(2)the using of transition-metal was avoided;(3)the synthetic steps were few.In a word,this present method provided a novel approach for the synthesis of 1,2-diarylindoles.