The Ullmann Condensation of Iodobenzanthronest

Abstract

In the course of the studies of biaryl syntheses of aromatic polycyclic hydrocarbons, the Ullmann condensation of 3- and 9-iodobenzanthrones were carried out. While 3-bromobenzanthrone gave 3, 3'-bibenzanthronyl [5] only in 13% yield, 3-iodobenzanthrone [3] gave [5] in 86% yield with the use of the same activated Cu powder.9, 9'-Bibenzanthronyl [4] (mp 399∼4O1°C) was obtained from 9-iodobenzanthrone [2] in 54% yield by the same procedure as [5]. Characteristic band at 336 nm in UV spectrum of [4] provides evidence for the presence of C-C bond between 9-positions of two benzanthrone nuclei. The ullmann condensation of equimolar mixture of [2] and [3] proceeded under the same reaction concition. The crude products were separated chromatographically to give new unsymmetrical diaryl compound, 3, 9'-bibenzanthronyl [6], in 22% yield, as yellow crystals (mp 388∼390°C). The structure was confirmed by IR and mass spectra, and satisfactory C, H analysis was obtained. The yield of [3] by direct iodination of benzanthrone with iodine and periodic acid was improved to 87% by the addition of small amount of H, SO₄.