RESUMO
We have recently developed an improved synthetic route to 1,1,2,2-tetrafluoroethanesulfonic acid (HCF2CF2SO3H, TFESA) and explored the applications of this newly available superacid in catalysis. Low volatility, ease of handling, and a convenient 1H NMR handle make this acid an attractive alternative to triflic acid. TFESA can also be converted to several of its derivatives: anhydride, sulfonyl chloride, and sulfonyl fluoride, which provide a good entry point for the synthesis of aryl sulfonates. We prepared several aryl esters of 1,1,2,2-tetrafluoroethanesulfonic acid (aryl tetraflates) and showed that they can be used in a number of palladium-catalyzed coupling reactions (Suzuki, Heck, and Buchwald-Hartwig couplings). While the reactivity of tetraflates lies between that of triflates and chlorides, tetraflates appear to be more thermally stable. Additionally, the presence of a hydrogen atom in the tetraflate group facilitates monitoring of reactions and characterization of derivatives.
Assuntos
Sulfonatos de Arila/síntese química , Hidrocarbonetos Fluorados/química , Ácidos Sulfônicos/química , Sulfonatos de Arila/química , Catálise , Espectroscopia de Ressonância Magnética/métodos , Estrutura Molecular , EstereoisomerismoRESUMO
We report our observation of solution photochemical reactions catalyzed by carbon nanotubes. Addition of sub-millimolar Ag+ ions into a solution of DNA-wrapped carbon nanotubes (DNA-CNT) leads to a strong charge-transfer band in the UV region of the optical absorption spectrum. Light irradiation of the Ag+/DNA-CNT mixture results in reduction of Ag+ to Ag nanoparticles and concomitant oxidation of water.
Assuntos
DNA/química , Nanotecnologia/métodos , Nanotubos de Carbono/química , Fotoquímica , Eletroquímica , Transferência de Energia , Soluções/química , Análise Espectral , Água/químicaRESUMO
Huisgen's 1,3-dipolar cycloadditions become nonconcerted when copper(I) acetylides react with azides and nitrile oxides, providing ready access to 1,4-disubstituted 1,2,3-triazoles and 3,4-disubstituted isoxazoles, respectively. The process is highly reliable and exhibits an unusually wide scope with respect to both components. Computational studies revealed a stepwise mechanism involving unprecedented metallacycle intermediates, which appear to be common for a variety of dipoles.
Assuntos
Cobre/química , Isoxazóis/síntese química , Triazóis/síntese química , Catálise , Cátions Monovalentes , Modelos Moleculares , Nitrilas/química , TermodinâmicaRESUMO
The oxidation of (tmeda)Pt(II)(CH(3))(2) (1, tmeda = N,N,N',N'-tetramethylethylenediamine) to (tmeda)Pt(IV)(OH)(OCH(3))(CH(3))(2) (3) by dioxygen in methanol proceeds via a two-step mechanism. The initial reaction between (tmeda)Pt(CH(3))(2) and dioxygen yields a hydroperoxoplatinum(IV) intermediate, (tmeda)Pt(OOH)(OCH(3))(CH(3))(2) (2), which reacts with a second equivalent of (tmeda)Pt(CH(3))(2) to afford the final product 3. Both 2 and 3 have been fully characterized, including X-ray crystallographic structure determinations. The effect of ligand variation on the oxidation of several dimethylplatinum(II) complexes by 2 as well as by dioxygen has been examined.