One of the two carbonyl groups of starting material 1,3-cyclohexandione (1) was condensed with phenylhydrazine hydrochloride to form monophenylhydrazone (2). 1,2,3,9-tetrahydro-carbazol-4-one (3) was prepared from 2 through cyclization and rearrangement in the presence of ZnCl2. Through methylation reaction, compound 3 is converted to 9-methyl-1,2,3,9-tetrahydro-carbazol-4-one (4). 3-Dimethylaminomethylsubstituted compound (5) was synthesized from 4 by Mannich reaction in glacial acetic acid. Nine novel 3-(...