Copper Causes Regiospecific Formation of C₄F₈‐Containing Six‐Membered Rings and their Defluorination/Aromatization to C₄F₄‐Containing Rings in Triphenylene/1,4‐C₄F₈I₂ Reactions

Abstract

The presence of Cu in reactions of triphenylene (TRPH) and 1,4-C4 F8 I2 at 360 °C led to regiospecific substitution of TRPH ortho C(β) atoms to form C4 F8 -containing rings, completely suppressing substitution on C(α) atoms. In addition, Cu caused selective reductive-defluorination/aromatization (RD/A) to form C4 F4 -containing aromatic rings. Without Cu, the reactions of TRPH and 1,4-C4 F8 I2 were not regiospecific and no RD/A was observed. These results, supported by DFT calculations, are the first examples of Cu-promoted 1) regiospecific perfluoroannulation, 2) preparative C-F activation, and 3) RD/A. HPLC-purified products were characterized by X-ray diffraction, low-temperature PES, and (1) H/(19) F NMR.

Fluorination‐Induced Evolution of Columnar Packing in Fluorous Triphenylenes and Benzotriphenylenes

“…In this work, an advanced synthetic strategy for perfluoroannulation reactions of TRPH with C 4 F 8 I 2 was developed. This strategy dramatically improved selectivity and regiospecificity, and resulted in two‐to‐three‐fold increases in the yields of the major products compared to the previous report . We hypothesized, based on earlier work with PAHs, that several key factors should favor the selective formation of symmetric TRPH(C 4 F 8 ) 3 , (i. e., 2,3 : 6,7 : 10,11‐(C 4 F 8 ) 3 ; see Figure for structure and abbreviations).…”

“…Our initial work on the trifluoromethylation of TRPH showed low selectivity in spite of D 3h symmetry of the core: several isomers with compositions TRPH(CF 3 ) 5,6,7 were formed in a 360 °C reaction with excess CF 3 I, and only one pure compound, C 1 ‐ TRPH(CF 3 ) 6 , was isolated in 25 % yield . An initial reaction of TRPH with C 4 F 8 I 2 at 360 °C yielded two major types of substitutions: (1) formation of six‐membered octafluorobutane cycles or (2) single substitutions of C 4 F 8 H groups . This reaction was non‐selective, and only a few small samples of purified derivatives could be isolated using HPLC.…”

“…This and many other R F . high‐temperature radical reactions of a variety of PAHs and excess of perfluoroalkyl iodide reagents typically exhibit low selectivity and yield multiple products ,,…”

“…of C 4 F 8 I 2 would be needed, in accordance with the previously proposed reaction mechanism (i. e., 2 equiv. of C 4 F 8 I 2 are required for each pair of adjacent C(sp 2 ) atoms) . Third, sufficiently high temperature should be used to promote the formation of the most thermodynamically stable isomers.…”

Experimental and DFT Studies of the Electron‐Withdrawing Ability of Perfluoroalkyl (RF) Groups: Electron Affinities of PAH(RF)n Increase Significantly with Increasing RF Chain Length

“…[22] Since that time we have prepared and studied R F derivatives of an umber of polycyclic aromatic hydrocarbons (PAHs), includingn aphthalene( NAPH), [23] anthracene (ANTH), [24] and CORA, [25][26][27] among others. [28][29][30][31] Here, we report experimental and/orD FT-predicted EAs of 13 homologous series of PAH(R F ) n compounds with one to six R F substituents. We show that changing the R F groupsf rom CF 3 to n-C 4 F 9 can increase the EA by up to four times the increasep reviously observed fort he C 60 (R F ) 2 compounds.…”