Synthesis of Spirocyclic Diarylfluorenes by One-Pot Twofold SNAr Reactions of Diaryl Sulfones with Diarylmethanes

Treatment of dibenzothiophene dioxides with cyclic diarylmethanes in the presence of KN(SiMe3)(2) results in the formation of fluorene-based spirocyclic tetraarylmethanes in a single operation. The transformation would proceed via an intermolecular SNAr reaction of the dioxides with cyclic diarylmethylpotassium followed by intramolecular SNAr cyclization. This straightforward strategy provides spirocyclic diarylfluorenes including unusual ones that are otherwise difficult to synthesize.