A NEW APPROACH TOWARDS THE SYNTHESIS OF BENZO[b]FLUORENE CORE

New approach towards a benzo[b] fluorene core is described. The model compound, 10-methoxy-11H-benzo[b]fluoren-11-one was prepared in five steps starting from dibenzylmalonic acid. The key step was the metal-catalyzed rearrangement of 3,3'-dihalo-2,2'-spirobiindan-1,1'-dione. The choice and proper activation of the metal was critical for assembly of the benzo[b] fluorenone system. The zinc-mediated rearrangement of the corresponding dibromo derivative led to the 10-hydroxy-11H-benzo[b]fluoren-11-one derivative in 52% yield. The structure of the product was established by spectroscopic methods and was additionally confirmed by standard methylation reaction to the 10-methoxy derivative, which is known in the literature.