Synthesis of 4-Substituted Indole Derivatives
Heterocycles January 1, 1977 S. Ohki, Tatsuo Nagasaka, Tohru Tuge 5 citations
A general synthetic method for producing 4-substituted indoles was developed. Fischer indolization of phenylhydrazones with a chlorine atom on the ortho position selectively gave 7-chloro-4-substituted indoles, which were then converted to 4-substituted indoles through catalytic hydrogenation. Cyclization of one derivative with polyphosphoric acid occurred at the 5-position of the indole ring, forming a tricyclic ketone. This approach addresses the difficulty of introducing substituents at the 4-position via intermolecular reactions and offers a useful route to 4-substituted indole derivatives, which are of interest due to the psychotomimetic activity of compounds like lysergic acid diethylamide and psilocybin.