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Site‐Selective Sonogashira Reactions of 1,4‐Dibromo‐2‐(trifluoromethyl)benzene: Synthesis and Properties of Fluorinated Alkynylbenzenes
Author(s) -
Reimann Sebastian,
Wittler Kai,
Schmode Stella,
Sharif Muhammad,
Fahrenwaldt Thomas,
Ludwig Ralf,
Spannenberg Anke,
Langer Peter
Publication year - 2013
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201300607
Subject(s) - chemistry , trifluoromethyl , sonogashira coupling , differential scanning calorimetry , liquid crystal , intramolecular force , proton nmr , carbon 13 nmr , context (archaeology) , crystallography , fluorine 19 nmr , absorption (acoustics) , selectivity , benzene , photochemistry , nuclear magnetic resonance spectroscopy , stereochemistry , organic chemistry , catalysis , palladium , physics , biology , thermodynamics , acoustics , optics , paleontology , alkyl
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 13 C NMR and 1 H– 13 C 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.