Cross dehydrogenative coupling via base-promoted homolytic aromatic substitution (BHAS): synthesis of fluorenones and xanthones.

Cross dehydrogenative coupling reactions occurring via base-promoted homolytic aromatic substitutions (BHASs) are reported. Fluorenones and xanthones are readily prepared via CDC starting with readily available ortho-formyl biphenyls and ortho-formyl biphenylethers, respectively. The commercially available and cheap tBuOOH is used as an oxidant. Initiation of the radical chain reaction is best achieved with small amounts of FeCp(2) (0.1 or 1 mol %).