The preparation of 5-indolyl-Mannich bases: an expedient source of 5-(chloromethyl)indoles

Regioisomeric analogues of gramine, 5-(dialkylaminomethyl)indole-2-carboxylates were prepared by the Fischer indolization of 4-(dialkylaminomethyl)phenylhydrazones easily obtained from diazotized 4-(dialkylaminomethyl)anilines by the Japp–Klingemann reaction. These formal Mannich bases are valuable synthetic intermediates affording 5-(chloromethyl)indoles on reaction with acetyl chloride at rt within a few minutes in quantitative yields.