The ionization of a series of benzyltriflones ArCH2SO2CF3 (Ar = C6H5, 4-CNC6H4, 4-NO2C6H4, 2,4-(NO2)2C6H3, 2,4,6-(NO2)3C6H2) has been studied kinetically and thermodynamically as well as by 1H, 13C, and 19F NMR in H2O−Me2SO mixtures and/or Me2SO. The findings that the acidity of the triflones is enhanced on going from hydroxylic solvents to Me2SO and that their deprotonation is associated with high Marcus intrinsic reactivities are two major results indicating the presence of a large polarizable charge density at Cα of the carbanionic species. Comparison of the results obtained with those for related arylnitromethane and arylacetonitrile compounds strongly supports this conclusion. NMR data add to the evidence that polarization rather than d−p π-resonance or negative hyperconjugation is the dominant factor in accounting for the capability of the strongly electron withdrawing SO2CF3 group to stabilize negative charge. Altogether, our results lead to a structural picture of the triflone carbanions in solution which does not totally fit the conclusions reached on the basis of solid-state or computed gas-phase studies.

chiral «-alkyl -hydroxy esters or acids with high optical purity were determined. This reaction has been now extended, with good results, to other substrates. Experimental SectionGeneral Methods.NMR spectra were recorded on a Perkin-Elmer (90 MHz) spectrometer using tetramethylsilane as an internal standard. Optical rotations were taken on a Perkin-Elmer 241 polarimeter using a 1-dm cell.Chiral Lithium Alkoxytrialkylaluminates. LiAl-:-Bu3OR*. This reagent can be prepared in stock quantities in the following manner: 5 g (30 mmol) of methyl phenylglyoxylate. After saponification of the -hydroxy ester la, 5.5 g (25 mmol) of crude acid (2a was obtained. Recrystallization in hexane-ethanol (94/6 by volume) gives 3.24 g (52% yield) of pure chiral -hydroxy acid 2a with 98% ee: [a]20D +19.6°(c 2.1, ethanol); mp 131 °C.

Perfluoroalkylation of electron-rich aromatic compounds with trifluoromethyl bromide, or long-chain perfluoroalkyl iodides, was performed in the presence of sodium dithionite or zinc-sulphur dioxide. This alkylation occurred at the ortho and para positions relative to the amino or hydroxy substituent. Pyrroles were perfluoroalkylated regioselectively at the 2-position. This alkylation was interpreted as a radical aromatic substitution; the formation of the perfluoroalkyl radical can be induced by a single-electron transfer from sulphur dioxide radical anion to the perfluoroalkyl halide.

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