Formation of basic compounds during the indole cyclization of ketone phenylhydrazones

✍ Scribed by Caterina Canu Boido; Vito Boido; Federica Novelli; Fabio Sparatore

• Book ID: 102339395
• Publisher: Journal of Heterocyclic Chemistry
• Year: 1998
• Tongue: English
• Weight: 444 KB
• Volume: 35
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570350412

✦ Synopsis

Abstract

On the basis of previous occasional findings, the Fischer indole cyclization of ten ketone phenylhydrazones containing moieties of increasing bulkiness was investigated in order to isolate eventual side products. In the cases of the three 2‐, 3‐ and 4‐acetylpyridine phenylhydrazones the corresponding 2‐pyridylindoles were the sole compounds so far isolated. In all the remaining cases, beside the indoles a mixture of basic compounds was obtained. In all cases aniline and a 2‐substituted (2‐methyl or 2‐phenyl)benzimidazole were formed, the last resulting through an apparent ortho‐semidinic rearrangements of phenylhydrazones. Starting from methyl isopropyl ketone phenylhydrazone a compound of formula C~11~H~15~NO was also isolated, to which the structure of 3‐(4‐aminophenyl)‐3‐methylbutanone was assigned on the basis of ir, nmr spectra and of the chemical reactivity. The formation of this compound seems related to a para‐benzidine‐like rearrangement of phenyl hydrazone.