RESUMO
Pentafluoropyridine was used as a molecular building block for the installation of aryl bromides, affording a series of multisubstituted halogenated arenes. This operationally simplistic methodology offers precise regioselectivity, ease of scalability, and high purity. 19F Nuclear magnetic resonance (NMR) served as a key diagnostic tool for structural characterization, given the sensitivity with various aryl bromine substitutions on the fluorinated pyridine ring. Furthermore, molecular modeling simulations offered insight into this new class of halogenated phenylpyridines and their unique electronic and reactive properties. This study also demonstrates examples of efficient chemo-selectivity upon either metal-catalyzed aryl-aryl coupling or nucleophilic aromatic substitution of the aryl bromide or fluorinated pyridine scaffold, respectively. A diverse pool of polyarylene structures with high degree of complexity, functionalized linear polymers, and controlled network architectures were achieved from this simple methodology.
RESUMO
The aryl diester compound, 2-methyl-1,4-phenyl-ene bis-(3,5-di-bromo-benzoate), C21H12Br4O4, was synthesized by esterification of methyl hydro-quinone with 3,5-di-bromo-benzoic acid. A crystalline sample was obtained by cooling a sample of the melt (m.p. = 502â K/DSC) to room temperature. The mol-ecular structure consists of a central benzene ring with anti-3,5-di-bromo-benzoate groups symmetrically attached at the 1 and 4 positions and a methyl group attached at the 2 position of the central ring. In the crystal structure (space group P), mol-ecules of the title aryl diester are located on inversion centers imposing disorder of the methyl group and H atom across the central benzene ring. The crystal structure is consolidated by a network of C-Hâ¯Br hydrogen bonds in addition to weaker and offset π-π inter-actions involving the central benzene rings as well as the rings of the attached 3,5-di-bromo-benzoate groups.