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Methylated, highly branched fluoroolefins were prepared by treatment of hexafluoropropene trimers with CH3Li and CH3MgBr. Their structures, which included some rotational isomers, were determined by NMR and GC-MS and were further confirmed by B3LYP-GIAO calculation of NMR shieldings. Of the seven methylated fluoroolefins isolated in pure states, three were shown to be mixtures of pairs of conformational isomers. The methylated fluoroolefins containing two bulky geminal substituents such as (CF3)2CF and (CF3)2CCH3 showed gear-meshed conformations in which the two bulky substituents were conformationally locked. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Enantiomerically pure α,α-dichloro β-fluoroalkyl γ-p-tolylthio γ-butyrolactones trans-6a–c have been obtained with excellent stereocontrol (> 98:2) and enantiomeric purity (> 98:2) by sulfoxide-directed lactonization (Marino's annu-lation reaction) of β-fluoroalkyl vinyl sulfoxides (R)-(E)-5a–c with dichloroketene. Highly chemoselective dechlorination and desulfurization reactions performed on trans-6c efficiently provided the β-chlorodifluoromethyl γ-butyrolactone (S)-8c, the absolute stereochemistry of which was determined by X-ray diffraction analysis of its γ-p-tolylthio precursor (2R,3S)-7c.