A new synthesis of indole 5-carboxylic acids and 6-hydroxy-indole-5-carboxylic acids in the preparation of an o-hydroxylated metabolite of vilazodone

A major metabolite of the potential antidepressant vilazodone formed in rat, dog, monkey and human liver microsomes is the 5-cyano-6-hydroxy-1H-indole derivative. For the construction of the salicyl-like substituted indole we adapted a synthesis of carmoxirole using Japp–Klingemann type Fischer-indole synthesis protocols. Functional group interconversion of carboxylic acid via carboxamide into cyanide was performed with methanesulfonic acid chloride.