Metal-free and regiospecific synthesis of 3-arylindoles
Chuangchuang Xu1, Wenlai Xie1, Jiaxi Xu1
1State Key Laboratory of Chemical Resource Engineering, Department of Organic Chemistry, College of Chemistry, Beijing University of Chemical Technology, Beijing 100029, P. R. China. jxxu@mail.buct.edu.cn.
Abstract:
A convenient, metal-free, and organic acid-base promoted synthetic method to prepare 3-arylindoles from 3-aryloxirane-2-carbonitriles and arylhydrazine hydrochlorides has been developed. In the reaction, the organic acid catalyzes a tandem nucleophilic ring-opening reaction of aryloxiranecarbonitriles and arylhydrazine hydrochlorides and Fischer indolization. The organic base triethylamine plays a crucial role in the final elimination step in the Fischer indole synthesis, affording 3-arylindoles regiospecifically. The reaction features advantages of microwave acceleration, non-metal participation, short reaction time, organic acid-base co-catalysis, and broad substrate scope.
More Related Videos
Related Concept Videos
Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene
Regioselective Formation of Enolates
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3
Preparation of 1° Amines: Azide Synthesis
Azide ions act as good nucleophiles and react with unhindered alkyl halides to form alkyl azides. Alkyl azides do not participate in further nucleophilic substitution reactions, thereby eliminating the chances of polyalkylated products. Alkyl azides are reduced by hydride-based reducing agents, like lithium aluminum...
Synthesis of α-Substituted Carbonyl Compounds: The Stork Enamine Reaction
Regioselectivity and Stereochemistry of Hydroboration
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.


