Currently, the chemistry of organofluorine compounds is a leading and rapidly developing area of organic chemistry. Fluorine present in a molecule largely determines its specific chemical and biological properties. This thematic issue covers the trends of organofluorine chemistry that have been actively developed in Russia the last 15 – 20 years. The review describes nucleophilic substitution and heterocyclization reactions involving fluorinated arenes and quinones and skeletal cationoid rearrangements in the polyfluoroarene series. The transformations involving CF3-substituted carbocations and radical cations are considered. Heterocyclization and oxidative addition reactions of trifluoroacetamide derivatives and transformations of the organic moiety in polyfluorinated organoboranes and borates with retention of the carbon – boron bond are discussed. Particular attention is devoted to catalytic olefination using freons as an efficient synthetic route to fluorinated compounds. The application of unsymmetrical fluorine-containing N-heterocyclic carbene ligands as catalysts for olefin metathesis is demonstrated. A variety of classes of organofluorine compounds are considered, in particular, polyfluorinated arenes and 1,2-diaminobenzenes, 1-halo-2-trifluoroacetylacetylenes, α-fluoronitro compounds, fluorinated heterocycles, 2-hydrazinylidene-1,3-dicarbonyl derivatives, imines and silanes. The potential practical applications of organofluorine compounds in fundamental organic chemistry, materials science and biomedicine are outlined. The bibliography includes 1019 references.

Keywords: Amides / Hydrodefluorination / Ab initio calculations / Nitrogen heterocycles / Zinc N-Acetylation of polyfluoroarylamines is proposed as a means to remove the amino group blocking effect of their hydrodefluorination by zinc in aqueous ammonia. With pentafluoroacetanilide, the Zn ion specific effect has been demonstrated to be responsible for ortho hydrodefluorination. This regiochemistry is accompanied by the removal of a fluorine atom from the para position, which occurs predominantly in the initial phase of the process in the absence of deliberately added zinc salt. The CuCl 2 additive has been found to accelerate the reaction and to propel it to double defluorination. Quantum chemical calculations suggest a diminished electron affinity of pentafluoroaniline, which is responsible for its inertness in relation to the hydrodefluorination reaction. The pentafluoroaniline radical anion, which essentially has a nonplanar structure, is prone to easy fragmentation to give an aminotetrafluorophenyl radical. For pentafluoroacetani-

The nitration of 2,3',4'-tricyanobiphenyl with subsequent transformations of the obtained product provided 4-X-2,3',4'-tricyanobiphenyls (X = NO 2 , NH 2 , NHCOCH 3 , Br, I). The condensation of the initial biphenyl or its 4-X-derivatives (X = NO 2 , NHCOCH 3 , Br, I) in the presence of zinc acetate afforded the corresponding zinc complexes of tetra(4-X-2-cyanophenyl)phthalocyanines.The interest to compounds from the phthalocyanine class notably grew recently due to the appearance of a number of their new applications in technology, chemical engineering, medicine etc. [1][2][3][4]. Because of the demand of materials with versatile properties a necessity arose of a wide variation in the structure of phthalocyanines that could be attained in two ways: either by the synthesis of "building blocks," or by the modifi cation of the already assembled phthalocyanines. In both events the presence in the molecule of the basic compounds of easily modifi ed fragments, e.g., of a phenyl group, is of fundamental importance. Besides, the arylsubstituted phthalocyanines possess their proper interest with respect to the practical application [2][3][4].The assembling of the aryl-substituted phthalocyanine core is performed with the use of arylated phthalonitriles as the "building blocks". The latter till recently were prepared by complex procedures [3,5], and this circumstance impeded the synthesis of this type phthalocyanines. The recently discovered reductive condensation of the proper phthalonitrile giving 2,3',4'-tricyanobiphenyl (I) [6] opened a short way to its derivatives and consequently to 2-cyanophenyl-substituted phthalocyanines based thereon. This study as the fi rst stage in the development of this research concerns the synthesis of 4-X-2,3',4'-tricyanobiphenyls (X = NO 2 , NH 2 , NHCOCH 3 , Br, I) and the preparation of phthalocyanines both from biphenyl I proper and its 4-X-substituted derivatives [7].The nitration of biphenyl I by analogy with the nitration of 2-chlorobenzonitrile [8] was performed by treating with concn. nitric acid at room temperature and afforded 4-nitro-2,3',4'-tricyanobiphenyl (II) containing 92% of the main substance with the yield of the purifi ed product of 50% (Scheme 1). Its formation is the natural result of the combined effect of all substituents present in the initial biphenyl.The reduction of compound II under the conditions analogous to those used in the reduction of 4-nitrobiphenyl [9] gave 4-amino-2,3',4'-tricyanobiphenyl (III) in 69% yield, and the threatment of the latter with acetic anhydride in DMSO resulted in 4-acetylamino-2,3',4'-tricyanobiphenyl (IV) in 57% yield (Scheme 1).Further modifi cation was performed by the diazotization of amine III followed by the transformations of diazonium salt V. In the dilute sulfuric acid at -10°C this salt formed in virtually quantitative yield as showed the formation of biphenyl I in a high yield at the treatment of the diazotization products with ethanol (Scheme 2).

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