Synthesis and Reactivity of Difluoroaromatic Compounds Containing Heterocyclic Central Groups

The reaction of trichloroacetaldehyde with fluorobenzene, followed by a series of transformations, gave 4-fluorobenzil and 4,4'-difluorobenzil which were used in the synthesis of new difluoroaromatic compounds with a heterocyclic central group. The ¹H, ¹³C, and ¹⁹F NMR spectra of the newly synthesized difluoroaromatic compounds were studied. The charge densities on the carbon atoms attached to fluorine were calculated in terms of the PM3 and AM1 semiempirical approximations. A correlation was found between the charge on C(F) and the corresponding ¹³C and ¹⁹F chemical shifts. Using this correlation, the reactivity of difluoroaromatic compounds in nucleophilic substitution reactions was estimated.     

New Activated Difluoroaromatic Compounds Containing Internal Acetylenic Moieties

New activated difluoroaromatic compounds having an internal acetylenic moiety were synthesized by reaction of trichloroacetaldehyde with fluorobenzene, followed by reaction with iodobenzene and cross coupling with acetylene in the presence of palladium complexes. According to the results of quantum-chemical calculations and ¹⁹F NMR data, the products are highly reactive compounds which can be used for the preparation of high-molecular-weight aromatic polyethers.     

Synthesis of new bis[p-(phenylethynyl)phenyl]hetarylenes and bis[p-(phenylglyoxalyl)phenyl]hetarylenes

A series of new bis[p-(phenylethynyi)phenyl]hetarylenes was obtained by cross-coupling between heteroaromatic dibromides and phenylacetylene catalyzed by phosphine complexes of palladium in the presence of Cul and an organic base. Bis[p-(phenylethynyl)phe-nyl]hetarylenes were oxidized to the corresponding bis[p-(phenylglyoxalyl)phenylihetarylenes using the I₂-DMSO system.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2359–2361, September, 1996.     

Synthesis of new aryl and hetaryl dibromides and diiodides,the monomers for preparation of polyarylene ethynylenes

Dibromides and diiodides with quinoxaline, phenylimidazole, and hexa- or pentaphenylarylene fragments were synthesized from dihalotolans obtained from chloral. Oligoarylene ethynylenes were synthesized by the reaction of the monomers with equimolar amounts of diethynyl aromatic compounds in the presence of the Pd^II complex. Oligomers with imidazole and hexa(penta)arylbenzene cycles are soluble in amide organic solvents and their reduced viscosities do not exceed 0.09 dL g^–1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1229–1235, May, 1996.