Dioxotetrahydro-1H-imidazo[1',5':1,2]pyrido[3,4-b] indole derivatives
show a high tendency towards the oxidation at the 11b-bridgehead posit
ion in basic media. This oxidation, affording the corresponding 11b-hy
droxy derivatives, is produced by reaction between atmospheric oxygen
and the imidazopyrido derivative under the enol form and can be suppre
ssed by working in inert atmosphere. In marked contrast, these imidazo
[1',5':1,2]pyrido derivatives are completely stable in acidic conditio
ns.