Efficient Synthesis of Fluorinated Phenanthrene Monomers Using Mallory Reaction and Their Copolymerization

Abstract

The Mallory reaction of 1,2-diarylhexa­fluoro­cyclopentene (1, aryl = 3-bromophenyl; 2, aryl = 4-bromophenyl) under light irradiation (λ = 365 nm) in the presence of iodide proceeded to give dibromo­phenanthrene derivatives, 3 and 4. Polycondensation of 9,9-dioctylfluorene-2,7-diboronic acid bis­(1,3-propanediol)­ester with the obtained monomers by Suzuki–Miyaura coupling afforded the phenanthrene-type copolymers Poly-3 and Poly-4 in high yields. For comparison, diphenylethene-type copolymers (Poly-1 and Poly-2) were also prepared analogously. UV–vis spectra of Poly-3 and Poly-4 in CHCl3 showed π–π* transition peaks at 380 and 354 nm, respectively, and additional shoulder peaks appeared at a longer wavelength in the film, suggesting the molecular assembly of the polymer molecules. In contrast, the spectra of Poly-1 and Poly-2 in solution were essentially unchanged as measured in the film, presumably owing to partial interruption of the π-conjugation system in polymer main chains. The copolymers showed photoluminesence (PL) in both CHCl3 and the film.

Reactivity and Mechanistic Issues in the Photocyclization of Dihalostyryl‐Naphthalenes towards Halo‐[4]helicenes: A Transposition on a Mallory Theme

“…In our initial report dedicated to the synthesis and properties of the first tetrathiafulvalene-helicene (TTF-Hel) derivatives as precursors for chiral electroactive materials, [14,24] we have described the oxidative photocyclization of 1 a as providing exclusively the 2,3-dibromo- [4]helicene 2 a (Scheme 4), [23] in agreement with similar regioselectivity observed for other meta-substituted bromo-stilbenes. [16][17][18] The dibromo-helicene 2 a was subsequently used in a bis-Stille coupling reaction to provide a protected helicene-bis(thiolate). However, a closer inspection now of the reaction products of the Mallory reaction on 1 a reveals that, besides 2 a, the monobromo derivative 4 a is also formed in a ratio 2 a:4 a of ~2:1 (Scheme 4).…”

“…[15] Intriguingly, the case of the bromine substituent in the meta position in a series of stilbenes has been only mentioned in a few reports describing the preparation of the corresponding phenanthrenes with the Br substituent in position 2, without any evidence for the formation of the other possible isomer with Br in position 4, which is one of the two inner positions in phenanthrenes. [16][17][18] The authors thus concluded that the ring closure reaction was highly regioselective, in spite of the yields observed for the various 2-Br-phenanthrenes reaching up to a maximum of 50 %. When the Br substituent is located in the para position, no regioselectivity issues occur.…”

Synthesis, Photophysical and Electrochemical Study of 1,3,6,8‐Tetraarylsubstituted X‐Shaped Phenanthrene Derivatives

“…[36] With these considerations in mind, we designed and synthesized several X-shaped phenanthrene derivatives that contain the same or different aryl substituents (π 1 and π 2 , Figure 1) at the 1,8-and 3,6-positions. The synthetic routes for preparation of these substances utilized photo-dehydrogenation cyclization reactions [37][38][39][40][41] of stilbenes containing two bromine and two chlorine groups. Suzuki coupling reactions of the poly-halogen substituted phenanthrenes, 1 and 2, produced in this manner generated the target phenanthrenes 3 a-c possessing four 4-tert-butylphenyl (t-Buph), 9,9-dimethyl-9Hfluoren-2-yl (DMFlu) or 4-diphenylaminophenyl (DPAP) groups (Figure 2).…”

Helicenes Fused with Hexafluorocyclopentene (HFCP): Synthesis, Structure, and Properties

“…Previously, we reported the syntheses of PAHs fused with HFCP, i.e., HFCP‐PAHs . Schemeà displays the synthetic route to these compounds.…”