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.

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A convenient and general method for the direct synthesis of 2-aryl-6-(trifluoromethyl)-4-pyrones and 2-aryl-5-bromo-6-(trifluoromethyl)-4-pyrones has been developed on the basis of one-pot oxidative cyclization of (E)-6-aryl-1,1,1-trifluorohex-5-ene-2,4-diones via a bromination/dehydrobromination approach. This strategy was also applied for the preparation of 2-phenyl-6-polyfluoroalkyl-4-pyrones and their 5-bromo derivatives. Conditions of chemoselective enediones bromination were found and the key intermediates of the cyclization of bromo-derivatives to 4-pyrones were characterized. Synthetic application of the prepared 4-pyrones has been demonstrated for the construction of biologically important CF3-bearing azaheterocycles, such as pyrazoles, pyridones, and triazoles.

Treatment of 6 trifluoromethylcomanic acid with sodium hydrosulfide afforded for the first time 4 oxo 6 trifluoromethyl 4H thiopyran 2 carboxylic acid (6 trifluoromethylthiocomanic acid). When heated or treated with H 2 SO 4 , this acid easily underwent decarboxylation leading to 2 trifluoromethyl 4H thiopyran 4 one. Because of this, both ethyl and methyl 6 tri fluoromethylthiocomanates were obtained in low yields (15-23%). Decarboxylation of 6 tri (di)fluoromethylcomanic acids gave 2 tri(di)fluoromethyl 4H pyran 4 ones in 77-80% yields.Key words: 6 tri(di)fluoromethylcomanic acid, 4 oxo 6 trifluoromethyl 4H thiopyran 2 carboxylic acid, decarboxylation, 2 trifluoromethyl 4H thiopyran 4 one, 2 tri(di)fluoromethyl 4H pyran 4 ones.Being highly reactive cyclic enones, fluoroalkylated γ pyrones are of interest as starting materials for the syn thesis of various partially fluorinated heterocyclic com pounds with a wide spectrum of useful properties. 1 How ever, only a few representatives of this class of compounds have been documented. The methods of their synthesis include fluoroacylation of acetyloxiranes, 2 2 alkoxyvinyl methyl ketone, 2 and 2 dimethylaminovinyl methyl ketone 3 and cyclization of bis(polyfluoroalkyl) 1,3,5 triketones. 4 The chemical properties of γ pyrones containing polyflu oroalkyl substituents are poorly studied, 3-6 mainly be cause these highly reactive compounds with three electro philic sites are not easily accessible. Recently, 7 we have demonstrated that ethyl 4 oxo 6 trifluoromethyl 4H py ran 2 carboxylate (1a) can easily be obtained by trifluoro acetylation of a sodium salt of ethyl 2,4 dioxopentanoate with ethyl trifluoroacetate and used for the synthesis of a number of new trifluoromethylated γ pyrones.In the present work, 6 trifluoromethylcomanic acid (2a) obtained by acid hydrolysis of ester 1a (see Ref. 7) was employed for the synthesis of 4 oxo 6 trifluorometh yl 4H thiopyran 2 carboxylic acid (6 trifluoromethyl thiocomanic acid, 3a) and its derivatives, including 2 trifluoromethyl 4H thiopyran 4 one (4a), a first repre sentative of trifluoromethylated γ thiopyrones. Results and DiscussionA reaction of acid 2a with aqueous NaSH at 50 °C for 20 min afforded for the first time acid 3a in 42% yield (Scheme 1). This is the first and so far sole example of a direct transformation of the γ pyrone ring into the γ thiopyrone one, because we failed with 6 difluorometh ylcomanic acid (2b), the nearest analog of acid 2a. A reac tion of acid 2b (obtained in 88% yield from ester 1b as described earlier 7 for compound 2a) with NaSH under similar conditions did not give 6 difluoromethylthioco manic acid. Only a small amount of the starting acid 2b was recovered from the reaction mixture; the application of more drastic conditions (90 °C, 1 h) resulted in resinifi cation. Note that key intermediates in the synthesis of nonfluorinated γ thiopyrones are thiacyclohexanones, which are oxidized under drastic conditions, and not easily accessible diacetylenic ketones. 8-10 In addition, 2,6 diaryl 4H thiop...

A novel convenient acid-catalyzed acylation of enaminodiones with acylbenzotriazoles via soft enolization has been developed for the direct synthesis of hard-to-reach 5-acyl-3-oxy-4-pyrones. The important advantages of the reaction include broad substrate scope, mild conditions, scalability, and readily isolation of products by crystallization without the use of chromatography. Further modification of the pyrone ring and synthesis of various azaheterocycles via ring-opening transformation have been demonstrated for the preparation of potential scaffolds for inhibition of metalloenzymes.