Synthesis of 3-substituted bacteriochlorophyll-d analogs and their self-aggregation in a nonpolar organic solvent

Zinc complexes of 3¹-epimerically pure 3²,3²,3²-trifluoro-bacteriopheophorbide-d methyl ester were prepared and their self-aggregation was examined in 1% (v/v) dichloromethane and hexane by visible and circular dichroism spectroscopies. Both the synthetic 3¹-trifluoromethylated diastereomers gave amorphous self-aggregates in the nonpolar organic solvent, while the corresponding nonfluorinated compounds possessing the 3¹-methyl group formed well-ordered and large oligomers similar to in vivo aggregates of bacteriochlorophyll-d in a chlorosome, a main light-harvesting antenna of green photosynthetic bacteria. The difference is ascribed to steric factor of the 3-CF₃ group, which was supported by optical properties of other synthetic zinc 3¹-hydroxy-13¹-oxo-chlorins possessing trifluoromethyl or secondary/tertiary substituents at the 3¹-position in the nonpolar organic solvent.     

Convenient syntheses of 1,1,1,3,3,3-hexafluoro-2-organyl-propan-2-ols and the corresponding trimethylsilyl ethers

A new convenient synthetic procedure to obtain various 1,1,1,3,3,3-hexafluoro-2-organyl-propan-2-ols and the corresponding trimethylsilyl ethers has been worked out starting from anhydrides or activated esters of carboxylic acids and trimethyl(trifluoromethyl)silane in the presence of tetramethylammonium fluoride. Conditions for the selective formation of 1,1,1,3,3,3-hexafluoro-2-organyl-propan-2-ols as well as the trimethylsilyl derivatives have been found.     

Development of Electrophilic Radical Perfluoroalkylation of Electron-Deficient Olefins

Fluorinated organic compounds have attracted significant attention over the past few decades owing to their unique properties and versatility. An established method for the synthesis of fluorinated organic compounds involves radical perfluoroalkylation reactions towards double bonds. In this radical pathway, electrophilic perfluoroalkyl radicals exhibit excellent reactivity towards electron-rich olefins. Therefore, several splendid perfluoroalkylation reactions of electron-rich olefins have been reported. However, there are only a few examples of reaction involving electron-deficient olefins because of their poor electronic compatibility with perfluoroalkyl radicals. This review focuses on the reports that challenge this long-standing issue. Radical perfluoroalkylation/bifunctionalization reactions of electron-deficient olefins are described according to the radical generation methods.     

Nucleophilic trifluoromethylation of arylidenemalononitriles

A method for the nucleophilic trifluoromethylation of arylidenemalononitriles using Me₃SiCF₃ is described. The reaction is carried out in dimethylformamide in the presence of AcONa as a Lewis base, and affords products of Michael addition in high yield.     

Trifluoromethylation of various aromatic compounds by CF3I in the presence of Fe(II) compound, H2O2 and dimethylsulfoxide

Trifluoromethylation of aromatic and hetero-aromatic compounds by CF₃I in the presence of Fe(II) compound, H₂O₂ and dimethylsulfoxide was investigated. Various trifluoromethylated benzene derivatives, six-membered nitrogen-containing aromatic compounds and five-membered hetero-aromatic compounds were obtained under mild conditions. General orientation of electrophilic substitution of aromatic compounds was observed similarly as reported in other radical trifluoromethylation previously.     

Transition-metal-free,visible-light-mediated regioselective C–H trifluoromethylation of imidazo[1,2-a]pyridines

A transition-metal-free, visible-light-induced trifluoromethylation of imidazo[1,2-a]pyridines has been developed at mild conditions by employing cheap and commercially available anthraquinone-2-carboxylic acid (AQN-2-CO₂H) as the photo-organocatalyst, and Langlois reagent as the trifluoromethylating reagent. A series of 3-(trifluoromethyl)imidazo[1,2-a]pyridine derivatives with broad functionalities could be conveniently and efficiently obtained by direct regioselective functionalization.     

Cinchona alkaloid-derived quaternary ammonium salt combined with NaH: a facile catalyst system for the asymmetric trifluoromethylation of ketones

Enantioselective trifluoromethylation of aromatic ketones promoted by the cinchona alkaloid-derived ammonium bromide and sodium hydride was described. A series of trifluoromethyl-substituted aryl alcohols could be obtained in up to 82% ee with 98% yield under mild conditions. A possible catalytic cycle was also presented.     

Trifluoromethylation of enamines under acidic conditions

A method for the trifluoromethylation of enamines using Me₃SiCF₃ leading to α-CF₃-substituted amines is described. The reaction is promoted by hydrofluoric acid generated from KHF₂ and either trifluoroacetic or triflic acid, and involves protonation of the enamine followed by transfer of the CF₃-carbanion from the silicon reagent to the cationic electrophile.     

Regiospecific synthesis and structural study of some trifluoromethyl substituted dibenzosemibullvalenes

Summary Preparation of the regiospecifically trifluoromethyl substituted dibenzosemibullvalenes3 and5 is described. An unequivocal proof of chirality of3 and5 was obtained by enrichment of their enantiomers using liquid chromatography on triacetyl- or tribenzoylcellulose. The stereostructure of compounds3 to5 was proved by their¹H-NMR spectra and confirmed by X-ray crystallographic analysis. The geometrical data from X-ray structural analyses showed that five-membered rings involved in the skeleton of3 and5 adopt flattened envelope conformations. These results indicate also a significant substituent-induced bond length asymmetry in the cyclopropane rings of3 and5.Presented at the XIIIth IUPAC Symposium on Photochemistry, University of Warwick, Coventry, England, 1990     

Nucleophilic trifluoromethylation: Some recent reagents and their stereoselective aspects

This review is a survey of several original reagents that have been designed, and are still under study, for nucleophilic trifluoromethylation. The starting materials were fluoral or trifluoroacetamides as well as trifluoromethanesulfinamides. Trifluoroacetamides or trifluoromethanesulfinamides derived from O-silylated-1,2-aminoalcohols constitute the most attractive family since they exhibit the larger scope and are able to trifluoromethylate enolizable as well as non-enolizable carbonyl substrates, even at room temperature when a substituent is present at the α-position relative to the nitrogen atom. Promising results have been obtained with some members of this family, concerning enantioselective trifluoromethylation of prochiral substrates.