Site‐Selective Sonogashira Reactions of 1,4‐Dibromo‐2‐(trifluoromethyl)benzene: Synthesis and Properties of Fluorinated Alkynylbenzenes

Abstract

Site‐selective Sonogashira cross‐coupling reactions of 1,4‐dibromo‐2‐(trifluoromethyl)benzene have been performed, affording a variety of functionalized alkynyl‐substituted (trifluoromethyl)benzenes. The site selectivity, in favor of position C‐4, was confirmed by 13C NMR and 1H–13C HMBC NMR measurements, X‐ray crystal structure analysis as well as DFT calculations. Furthermore, the mesomorphic properties and optical textures were examined by differential scanning calorimetry and polarized optical microscopy. Several dialkynyl‐substituted (trifluoromethyl)benzenes showed nematic liquid‐crystalline properties over a long phase range. The influence of terminal and lateral substituents on the formation and stability of the molecular network within the liquid‐crystalline phase is explained by the results of DFT calculations. Additionally, the absorption and fluorescence properties were analyzed in detail. The intramolecular influence of electron‐donating or electron‐withdrawing groups and also of solvatochromatism are considered. In this context, time‐dependent B3LYP/6‐31G* (TD‐B3LYP) calculations were carried out to characterize the main absorption bands.

Practical tetrafluoroethylene fragment installation through a coupling reaction of (1,1,2,2-tetrafluorobut-3-en-1-yl)zinc bromide with various electrophiles

“…To be further convinced of the importance of the present reaction, we carried out an additional transformation of the coupling adduct 4n to a CF 2 CF 2 -containing π-conjugates molecule, a fluorinated tolane derivative, applicable to promising functional materials, such as light-emitting and liquid-crystalline materials ( Scheme 3 ) [ 39 – 44 ].…”

Polycyclic Aromatic Hydrocarbons Bearing Polyethynyl Bridges: Synthesis, Photophysical Properties, and their Applications

“…Li and Hu reported organic compounds consisting of ethynyl bridges (80)(81)(82) which were employed in construction of OFET devices (Figure 5). [106] CV studies revealed the irreversible redox behavior of compounds 80 and 81 and quasi- reversiblity behavior of 82.…”

“…Among the trifluoromethyl substituted alkynylated compounds 51 , 52 and 54 (Figure 1), both 51 and 52 displayed four transitions in their absorption spectra [81] . Due to the mesomeric and electron inductive effect, the compounds containing electron‐donating groups ( 51 b – g , 52 b – g ) demonstrated redshift in absorption as well as in emission spectra.…”

“…In this case, site‐selective coupling reaction occured on iodine containing carbon over the fluorine containing carbon atoms. The Langer group went on to describe the synthesis of mono and dialkynylbenzene starting from aryl bromides (Scheme 15) [81] in presence of trifluoromethyl group.…”

“…Among the trifluoromethyl substituted alkynylated compounds 51, 52 and 54 (Figure 1), both 51 and 52 displayed four transitions in their absorption spectra. [81] Due to the mesomeric and electron inductive effect, the compounds containing electron-donating groups (51 b-g, 52 b-g) demonstrated redshift in absorption as well as in emission spectra. Notably, 4,4'-((2-(trifluoromethyl)-1,4-phenylene)bis(ethyne-2,1-diyl))bis (methoxybenzene) (52 g) exhibited the highest Stokes shift (47 nm) which can be attributed to the push-pull effect of electron-donating nature of À OCH 3 and electron-withdrawing nature of À CF 3 .…”