Bhanuchandra, M. published the artcileSynthesis of Spirocyclic Diarylfluorenes by One-Pot Twofold SNAr Reactions of Diaryl Sulfones with Diarylmethanes, Category: naphthyridine, the publication is Organic Letters (2016), 18(3), 384-387, database is CAplus and MEDLINE.
Treatment of dibenzothiophene dioxides I (R1 = R2 = H; R1 = 2-Ph, R2 = H, 9-Ph; R1 = 3-Cl, R2 = 7-Cl; etc.) with cyclic diarylmethanes II (X = nothing, CH2, CMe2, O, S, R3 = H; X = S, R3 = OH, MeO, CF3, Ph, etc.) in the presence of KN(SiMe3)2 resulted in the formation of fluorene-based spirocyclic tetraarylmethanes III in a single operation. The transformation proceeds via an intermol. SNAr reaction of the dioxides with cyclic diarylmethylpotassium followed by intramol. SNAr cyclization. This straightforward strategy provides a wide range of spirocyclic diarylfluorenes including unusual ones that are otherwise difficult to synthesize.
Organic Letters published new progress about 159-62-6. 159-62-6 belongs to naphthyridine, auxiliary class Other Aromatic Heterocyclic,Spiro, name is Spiro[fluorene-9,9′-xanthene], and the molecular formula is C25H16O, Category: naphthyridine.
Referemce:
https://en.wikipedia.org/wiki/1,8-Naphthyridine,
1,8-Naphthyridine | C8H6N2 – PubChem