Der F<scp>ISCHER</scp>'sche Indolringschluss mit 1, 3‐disubstituierten 4‐Piperidonen. 7. Mitteilung über synthetische Indolverbindungen [1]

Abstract

Abstract Treatment of the arylhydrazones of 1, 3‐disubstituted 4‐piperidones with ethanolic hydrogen chloride (F ISCHER reaction conditions) affords 1, 2, 3, 4‐tetrahydropyrimido [3, 4‐a]‐indoles in good yields. During catalytic hydrogenation in the presence of protons these tetrahydropyrimido‐indoles are split into 2‐(2‐methylamino‐ethyl)‐indoles. The formation of these tricyclic products can be explained by rearrangement immediately following the normal F ISCHER reaction. If the substituent at the piperidine nitrogen is an acyl group, normal or rearranged products are formed, depending on the nature of the 3‐substituent.