Collect. Czech. Chem. Commun. 2005, 70, 223-236

Synthetic Utility of 2-Benzylidene-1,2,3,4-tetrahydrocarbazol-1-ones. A Facile Syntheses of Pyrano[2,3-a]carbazoles, Pyrido[2,3-a]carbazoles and Pyridazino[3,4-a]carbazoles

Isravel Antony Danish and Karnam Jayarampillai Rajendra Prasad*

Department of Chemistry, Bharathiar University, Coimbatore 640146, India


2-Benzylidene-1,2,3,4-tetrahydrocarbazol-1-ones 1, synthons easily accessible from the corresponding 1,2,3,4-tetrahydrocarbazol-1-ones, were utilized in the synthesis of fused carbazoles. In accordance, the reaction of 1 with malononitrile yielded pyrano[2,3-a]carbazoles 2a and 2d or pyrido[2,3-a]carbazoles 2b, 2c and 2e. The reaction of 1 with thiocarbohydrazide or thiosemicarbazide under basic conditions afforded pyridazino[3,4-a]carbazoles 3 or thiol substituted pyridazino[3,4-a]carbazoles 4, respectively, in good yields. The formation of the hitherto unknown compounds was well supported by plausible mechanisms. The products formed were characterized by IR, 1H NMR, 13C NMR, mass spectral methods and by elemental analysis.

Keywords: 2-Benzylidene-1,2,3,4-tetrahydrocarbazol-1-ones; Aldol condensation; Malononitrile; Pyrano[2,3-a]carbazoles; Pyrido[2,3-a]carbazoles; Thiocarbohydrazide; Thiosemicarbazide; Pyridazino[3,4-a]carbazoles.

References: 18 live references.