One-Step Formation of a Decasubstituted Phenanthrene by Coupling and Fragmentation of a Smaller Precursor

Abstract

When 8-bromo-1,2,3,4,5,6,7-heptaphenyl-1,4-dihydro-1,4-epoxynaphthalene (5) is heated with copper powder and no solvent at 340 °C under argon, the chief product is 1,8-dibenzoyl-2,3,4,5,6,7,9,10-octaphenylphenanthrene (6) in yields as high as 68 %. The reaction appears to involve Ullmann coupling of 5 and expulsion of two molecules of diphenylacetylene to give a decaphenyl bis(isobenzofuran) which then undergoes intramolecular cyclization and fragmentation to yield phenanthrene 6.