Mixed aldol condensation of 2,3,4,9-tetrahydrocarbazol-1-ones with 3,4-dimethoxybenzaldehyde (veratraldehyde) yielded 2-(3′,4′-dimethoxybenzylidene)-2,3,4,9-tetrahydrocarbazol-1-ones. These enones on reaction with hydrazine hydrate, hydroxylamine hydrochloride, malononitrile and guanidinium nitrate under different conditions yielded the corresponding pyrazolo[3,4-a]-, isoxazolo[3,4-a]-, pyrido[2,3-a]-, and pyrimido[4,5-a]-carbazoles respectively. The molecular and crystal structure of 2-(3′,4′-dimethoxybenzylidene)-2,3,4,9-tetrahydro-1H-carbazol-1-one resolved by single crystal X-ray diffraction is discussed.