Denoising of image sequences with motion-adaptive orthogonal wavelets

Pure -1,2,3,9-tetrahydro-9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]-4H-carbazol-4-one or a pharmaceutically acceptable salt thereof is prepared in a high yield by a simple process which reacts 1,2,3,9-tetrahydro-9-methyl-4H-carbazol-4-one with a 2-methylimidazole derivative in an organic solvent or in a mixture of an organic solvent and water in the presence of a halosilane compound.