From Targeted Synthesis to Serendipitous Discovery: Transforming Perfluorotoluene into Discotic Liquid Crystals and Dearomatized Spirofluorenes

This study develops a one-pot synthetic system that concurrently produces two classes of functional materials via a previously unobserved transformation of perfluorotoluene under nucleophilic conditions. Building on prior work with fluorinated discotic systems, the reaction of 2,2′-dilithio-1,1′-biaryls with perfluorotoluene (C 6 F 5 –CF 3 ) furnishes trifluoromethylated trifluorotriphenylene derivatives ( TPF n, n = 1–4, 6, 8, 10, 8/2) alongside structurally distinct dearomatized spirofluorene analogues ( TPF n -1). The formation of the spirofluorene compounds points to a competing pathway beyond classical aryl nucleophilic substitution. Based on structural evidence, a dearomatization process involving cleavage of four C–F bonds (one from the pentafluorophenyl ring and three from the CF 3 group) and subsequent formation of new C–C bonds is proposed to account for the formation of the spiro-fused architecture. This side reaction sheds light on the moderate yields of the target TPF n series and highlights the complex reactivity of perfluorotoluene with 2,2′-dilithio-1,1′-biaryls. All TPF n compounds form thermally stable hexagonal columnar (Col hex ) mesophases with large liquid-crystalline ranges, along with a strong modulation of the clearing temperatures with alkoxy chain lengths. Despite the presence of the bulky lateral CF 3 group, the transition temperatures are surprisingly not greatly affected when compared to previously synthesized 4 F - TP n homologous compounds (with no CF 3 groups). Structural analysis, supported by X-ray crystallography of di tert -butyl model compound (tBu TPF ), validates the molecular design and packing. This work thus provides a practical one-pot route to potentially fluorinated discotic semiconductors while revealing a competing transformation that advances the understanding of polyfluorinated arene chemistry and offers access to novel spiro-fused molecular architectures.