POCl3 mediated one-pot deoxygenative aromatization and electrophilic chlorination of dihydroxy-2-methyl-4-oxo-indeno[1,2-b]pyrroles

Abstract

A class of indenopyrroles is presented by the treatment of known dihydroxy-2-methyl-4-oxoindeno[1,2-b]pyrroles with phosphorus oxychloride (POCl₃). The elimination of vicinal hydroxyl groups at the 3a and 8b positions, formation of a π bond, and electrophilic chlorination of the methyl group attached to C² resulted in the fused aromatic pyrrole structures. Benzylic substitution of various nucleophiles such as H₂O, EtOH, and NaN₃ with a chlorine atom gave diverse 4-oxoindeno[1,2-b]pyrrole derivatives in 58 to 93% yields. The reaction was investigated in different aprotic solvents, and the highest reaction yield was obtained in DMF. The structures of the products were confirmed by spectroscopic methods, elemental analysis, and X-ray crystallography.