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Singlet diradicals are usually not energy minima. As observed by femtosecond spectroscopy, they readily couple to form final sigma bonds. Substituent effects allow lifetimes to increase into the microsecond range. Taking advantage of the properties of hetero-elements, a diradical has been prepared that is indefinitely stable at room temperature. The availability of diradicals that can be handled under standard laboratory conditions will lead to further insight into their chemical and physical properties, raising the likelihood of practical applications, especially in the field of molecular materials such as electrical conductors and ferromagnets.

Cu(I)-diamine complexes were found to catalyse the trifluoromethylation of aryl iodides. In the presence of a small amount of CuX (X = Cl, Br, I) and 1,10-phenanthroline (phen), the cross-coupling reactions of iodoarenes with trifluoromethylsilanes proceeded smoothly to afford trifluoromethylated aromatics in good yields.

A new methodology for aromatic difluoromethylation is described. Aryl iodides reacted with α-silyldifluoroacetates upon treatment with copper catalyst in DMSO or DME to give the corresponding aryldifluoroacetates in moderate to good yields. The subsequent hydrolysis of aryldifluoroacetates and KF-promoted decarboxylation afforded a variety of difluoromethyl aromatics.

2,2-Difluoro enol silyl ethers were readily prepared by Mg 0 promoted selective defluorination of trifluoromethyl ketones in the presence of TMSCl, which involves C-F bond cleavage.

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[figure: see text] Under hydrogen pressure, a catalytic amount of palladium(II) trifluoroacetate and 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) promoted asymmetric hydrogenation of alpha-fluorinated iminoesters to afford highly enantioenriched beta-fluorinated alpha-amino esters. The yield and ee were much improved by employing fluorinated alcohols such as 2,2,2-trifluoroethanol (up to 91% ee).

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