Metal-free and regiospecific synthesis of 3-arylindoles

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 aryloxiranecarbonitril...

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Bibliographic Details
Published in:Organic & biomolecular chemistry 2020-04, Vol.18 (14), p.2661-2671
Main Authors: Xu, Chuangchuang, Xie, Wenlai, Xu, Jiaxi
Format: Article
Language:English
Subjects:
Acceleration
Catalysis
Hydrochlorides
Indoles
NMR
Nuclear magnetic resonance
Optimization
Organic acids
Reaction time
Ring opening
Substrates
Triethylamine
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Summary: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. A microwave-assisted acid and base co-catalyzed strategy shows high efficiency in the synthesis of 3-arylindoles through tandem nucleophilic ring-opening and Fischer indolization of aryloxiranecarbonitriles and arylhydrazine hydrochlorides.
ISSN:1477-0520
1477-0539
DOI:10.1039/d0ob00317d