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 a wide range of spirocyclic diarylfluorenes including unusual ones that are otherwise difficult to synthesize.