One-Pot Synthesis of Spiro-isobenzofuran Compounds via the Sequential Condensation/Oxidation Reaction of Ninhydrin with 4-Amino-1,2-naphthoquinones/2-Amino-1,4-naphthoquinones under Mild Conditions

A one-pot route for the synthesis of spiro-isobenzofuran compounds was developed via the condensation reaction of ninhydrin with 4-amino-1,2-naphthoquinones or 2-amino-1,4-naphthoquinones in acetic acid followed by the oxidative cleavage of the corresponding vicinal diols at room temperature. Various derivatives of spiro[benzo[g]indole-2,1'-isobenzofuran]-3,3',4,5(1H) tetraones and spiro[benzo[f]pyrrolo[2,3-h]quinoxaline-2,1'-isobenzofuran]-3,3'(1H)-diones were synthesized in good to high yields. Moreover, further condensation of spiro[benzo[g]indole-2,1'-isobenzofuran]-3,3',4,5(1H)-tetraones with 1,2-diamines resulted in the new spiro-isobenzofuran compounds having phenazine rings in high yields.