A facile microwave assisted synthesis and spectral characterization of substituted benzylidine carbazoles, pyrazolo[3,4-a]carbazoles and isooxazolo[3,4-a]carbazoles.

Aldol condensation between 1-oxo-1,2,3,4-tetrahydrocarbazole 1 and benzaldehyde yielded 2-benzylidine-1-oxo-1,2,3,4-tetrahydrocarbazole 2. Which on treatment with hydrazine hydrate in ethanol afforded substituted 4,5-dihydro-3-phenyl-2Hpyrazolo[ 3,4-a]carbazoles 3. The compound 2 on treatment with hydroxylamine hydrochloride in ethanol yielded 3-phenyl isooxazolo[3,4-a]carbazoles 4. Microwave irradiation of 2 with hydrazine hydrate and hydroxylamine hydrochloride in ethanol separately yielded the same products 3 and 4 respectively.

Microwave assisted synthesis and spectral studies of 2-thiophen-2-ylmethylene-2,3,4,9-tetrahydro-carbazol-1-one,3-thiophen-2-yl-4,5-dihydro-10h-2-oxa-1,10-diaza-cyclopenta[a]carbazole and 3-thiophen-2-yl-2,4,5,10-tetrahydro-1,2,10-triaza-cyclopenta[a]carbazole derivatives.

Microwave assisted new aldol condensation reaction of 1-oxo-1,2,3,4- tetrahydrocarbazoles 1 with thiophene-2-carbaldehyde 2 in the presence of alcoholic KOH affords a single product 2-Thiophen-2-ylmethylene-2,3,4,9-tetrahydro-carbazol-1-one 3. 3 on irradiation with hydroxylamine hydrochloride yielded 3-Thiophen-2-yl-4,5-dihydro-10H-2-oxa-1,10-diazacyclopenta[ a]carbazole 4 and 3 on irradiation with hydrazine hydrate in ethanol medium to yielded 3-Thiophen-2-yl-2,4,5,10-tetrahydro-1,2,10-triaza-cyclopenta[a]carbazole 5. The structures of the synthesized compounds were confirmed on the basis of physical and spectral analysis (FT-IR, 1H, 13C-NMR) and Mass spectral data.