Reactivity and structure of CF3I on Ru(001)
A variety of surface-sensitive techniques are used to elucidate the reaction pathways, as well as adsorbate structures, associated with thermal activation of CF{sub 3}J following adsorption on Ru(001) at 100 K. XPS shows that the C-I bond of CF{sub 3}I dissociates below 200 K to form CF{sub 3}(ad) and I(ad); the subsequent reactions of CF{sub 2} are best viewed as being regulated by the availability of surface sites. CF{sub 3}(ad) dissociates to CF{sub 2}(ad) below 200 K. Further CF{sub 3} dissociation, some of which is activated by H(ad), occurs between 200 and 400 K until all available sites are filled. Desorption of the remaining CF{sub 3}, peaking at 705 K, once again opens surface sites for decomposition. This is followed by recombination of the products to form CF{sub 3}(g). No evidence for CF(ad) is ever observed. Hydrogen coadsorption studies explain interesting features associated with fluorine evolution. HREELS and ESDIAD results indicate that CF{sub 3} adopts a tilted configuration on Ru(001). 53 refs., 11 figs., 3 tabs.
Catalysis for fluorination and trifluoromethylation
Recent advances in catalysis have made the incorporation of fluorine into complex organic molecules easier than ever before, but selective, general and practical fluorination reactions remain sought after. Fluorination of molecules often imparts desirable properties, such as metabolic and thermal stability, and fluorinated molecules are therefore frequently used as pharmaceuticals or materials. But the formation of carbon−fluorine bonds in complex molecules is a significant challenge. Here we discuss reactions to make organofluorides that have emerged within the past few years and which exemplify how to overcome some of the intricate challenges associated with fluorination.
Highly enantio- and diastereoselective synthesis of β-methyl-γ-monofluoromethyl-substituted alcohols.
Enanatiopure β-methyl-γ-monofluoromethyl alcohols were prepared from the allylic alkylation between fluorobis(phenylsulfonyl)methane with Morita-Baylis-Hillman carbonates. The reaction was catalyzed by using the Cinchona alkaloid derivative, (DHQD)(2)AQN. The origin of the stereoselectivity was verified by DFT methods. Calculated geometries and relative energies of various transition states strongly support the observed stereoselectivity.