Synthesis of 4-Substituted Indole Derivatives
S. Ohki, Tatsuo Nagasaka, Tohru Tuge
Heterocycles 1977 DOI: 10.3987/s(s)-1977-01-0371 (opens in new tab)
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AI-extracted from the abstract| Characteristics | Theoretical or philosophical paper Peer reviewed |
|---|---|
| Keywords | Indole test Ring chemistry Substituent Intramolecular force Chlorine atom Ketone Stereochemistry Alkoxy group Medicinal chemistry Organic chemistry |
| Citations | 5 |
| Key points | Proposes that Fischer indolization of phenylhydrazones with a chlorine atom on one ortho position selectively yields 4-substituted indoles. |
Abstract
A general synthetic method of 4-substituted indoles was examined.The Fischer indolization of phenylhydrazones (2, 3, 7, and 8) having chlorine on & position gave 7-chloro-4-substituted indoles (4, 9, and lo), which were converted to 4-substituted indoles (5 and 13) by catalytic hydrogenation.Cyclization of 3-(2-ethoxy~arbonyl-7-chloroindol-4-yl)propionic acid (10) with polyphosphoric acid (PPA) took place at the 5-position of indole ring to give a tricyclic ketone (14).4-Substituted indole derivatives have ken of interest for many years because of the psychotamimetic activity of ampunds such as lysergic acid diethylamide CUD) and psilocybin.2The intramolecular cyclization reaction to 4-position of indole ring has been reported recently."However introduction of a certain substituent to 4-position by intermolecular reaction seem mre difficult.4In this paper we wish to report the useful syretic method of 4-substituted indole derivatives.The Fischer indolization of 3-substituted phenylhydrazone gives a mixture of 4-and 6-substituted indoles.' 4-Substituted indoles m y be selectively obtained from the phenylhydrazones (such as 2, 3, 7, and 8) having chlorine atom on the one ortho position.6Rawever, it was reported by Ishii et that the Fischer