Synthesis of pyrimido annelated carbazoles and 2-methyl-6-oxo-bisindolo [1,2-b5,4-b'] cyclohexanones using 2-hydroxymethylene-1-oxo-1,2,3,4-tetrahydrocarbazoles

Treatment of 2-hydroxymethylene-1-oxo-1,2,3,4-tetrahydrocarbazoles la-d with guanidine nitrate affords 2-amino-4-hydroxy-1,4,5,6-tetrahydropyrimido[4,5-a]carbazoles 2a-d. In another reaction, 2-hydroxymethylene-1-oxo-1,2,3,4-tetrahydrocarbazoles la-d are treated with diazotized p-toluidine under Japp-Klingemann conditions to furnish the respective 4'-methyl-1-oxo-2-phenylhydrazono-1,2,3,4-tetrahydrocarbazoles 3a-d, which upon cyclisation using Kent's reagent (CH 3 COOH : HCl, 4:1) yield the corresponding 6,12-dihydro-2-methyl-6-oxo-bisindolo[ 1,2-b:5,4-b']cyclohexanones 5a-d.