Syntheses of novel derivatives of 2-acetylfuro[2,3-a]carbazoles, benzo[1,2-b]-1,4-thiazepino[2,3-a]carbazoles and 1-acetyloxycarbazole-2-carbaldehydes

An elegant one pot syntheses of the titled compounds 3a-d, 4a-d and 6a-d have been presented starting from 1-hydroxycarbazole-2-carbaldehydes 2a-d in good yields. Treatment of 1-hydroxycarbazole-2-carbaldehydes 2a-d with chloroacetone and with o-aminothiophenol have afforded the novel 2-acetylfuro[2,3-a]carbazoles 3a-d and benzo-[1,2-b]-1,4-thiazepino[2,3-a]carbazoles 4a-d respectively. Further carbazoles 2a-d are treated with phenyl acetic acid in an attempt to synthesize 3-phenyl-2-oxopyrano[2,3-a]-carbazoles 5ad, but the reaction did not proceed in the anticipated direction and only acetyl derivatives 6a-d are obtained. All the products thus obtained from these reactions are well characterized by spectroscopic and analytical data.