RESUMO
The gold(I)-catalyzed cycloisomerization of 1,5-enynes and 1,4-allylallenes to tetracyclododecane and tetracyclotridecane derivatives, respectively, is reported. Complexation of the cationic gold(I) complex to either the alkyne or allene moiety induces an intramolecular addition of the alkene, leading to a gold(I)-stabilized carbenoid intermediate. This intermediate undergoes a formal sp(3) C-H insertion to generate the tetracyclic adduct. A series of deuterium labeling experiments showed that the C-H functionalization step proceeds with an inverse kinetic isotope effect.
Assuntos
Alcinos/química , Compostos Alílicos/química , Hidrocarbonetos Aromáticos com Pontes/síntese química , Ouro/química , Catálise , Cátions Monovalentes/química , Ciclização , IsomerismoRESUMO
The behavior of Fe(III) aquacomplexes in TiO(2) suspensions in the degradation of phenol has been investigated. The most active Fe(OH)(2+) species adsorbed on the surface of TiO(2) retards the conversion of Fe(OH)(2+) into oligomers and therefore increases the percentage of Fe(OH)(2+) with irradiation time, with a consequent enhancement in the catalytic cycle of Fe(III)/Fe(II) and excited charge traps by Fe(III) in the iron-TiO(2) system. The influence of iron addition on TiO(2) was obtained when the regeneration of [Fe(OH)(2+)] remained continuous with irradiation time. In an optimum TiO(2) suspension (0.5g/L) with the addition of 0.1mM Fe(III), the measured k(obs) values for phenol degradation were enhanced for the higher adsorption of Fe(OH)(2+) on the reactive surface of TiO(2) at a specified irradiation time.
Assuntos
Compostos Férricos/análise , Ferro/química , Fenóis/química , Fenóis/efeitos da radiação , Titânio/análise , Adsorção , Catálise , Radical Hidroxila , Luz , Oxidantes , Fotoquímica , Espectrofotometria UltravioletaRESUMO
Gold catalyzed intermolecular addition of alcohols toward the proximal allenic double bond of 4-vinylidene-2-oxazolidinones gives hydroalkoxylation products, which can be easily converted into the corresponding novel spiro dihydrofuran or dihydropyran derivatives in high yield.
RESUMO
14π-Electrocyclization across the two pentafulvenoid moieties of pentafulvene 1 occurs upon heating to provide dicyclopenta[a,d]cyclooctene 2 [Eq. (1)]. The nonalternant hydrocarbon 2 shows diatropic character and a distinctive absorption spectrum with the longest wavelength maximum at 767 nm.