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Silica gel assisted reductive cyclization of 2‐nitro‐β‐piperidinostyrenes, derived from 2‐nitrotoluenes, to indoles
Author(s) -
Kawase Masami,
Sinhababu Achintya K.,
Borchardt Ronald T.
Publication year - 1987
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570240602
Subject(s) - chemistry , silica gel , nitro , toluene , column chromatography , acetic acid , organic chemistry , condensation , chromatography , alkyl , physics , thermodynamics
An efficient modification of the Leimgruber‐Batcho method of indole synthesis has been devised that facilitates the synthesis of a variety of 2,3‐unsubstituted indoles containing halogen, methoxy and benzyloxy groups, from 2‐nitrotoluenes, in high yields. The modified method involves the condensation of 2‐nitrotoluenes with tripiperidinomethane followed by the reductive cyclization of the intermediate 2‐nitro‐β‐piperidinostyrenes with iron and acetic acid in refluxing toluene in the presence of silica gel (column chromatography grade, 60–200 mesh).