Synthesis of new hexahydro-5H-indolo[3,2-c]acridines and indolylbutanoic acids by Fischer cyclization of arylhydrazones

Abstract

Arylhydrazones of 2,3,5,6,7,8-hexahydroacridin-4(1H)-ones and 7-amino-6-(arylhydrazono)-7-oxoheptanoic acids were cyclized by Fischer reaction, providing previously unknown polysubstituted indole derivatives. The starting hydrazones were synthesized under Japp–Klingemann reaction conditions by using 1,2,3,4,5,6,7,8-octahydroacridine-4-carboxamide and 2-oxocyclohexanecarboxamide as starting materials. It was established from the spectral data that the obtained 7-amino-6-(arylhydrazono)-7-oxoheptanoic acids existed as mixtures of (Z)- and (E)-isomers, but were converted to an individual (Z)- or (E)-isomer in DMSO solution.