Reductive Coupling of Allylic Esters with Carbonyl Compounds Mediated by the Mischmetall/[SmI2/Pd0cat.′]cat. System
作者:Sédami Médégan、Florence Hélion、Jean-Louis Namy
DOI:10.1002/ejoc.200500291
日期:2005.11
“two-stage catalysis” has been carried out using SmI2 and Pd(PPh3)4 in catalytic amounts together with mischmetall (an alloy of the light lanthanides) as a co-reductant. A catalytic scheme that takes into account previously reported reactions of SmI2/Pd0cat. and mischmetall/SmI2,cat. systems is proposed. It has also been shown that palladium complexes catalyse the addition of organolanthanide species
The reaction of 1-arylpropenyl-lithium (1a–c) with t-alkylbromides proceeds by either a nucleophilic substitution or single electron transfer mechanism, the preferred pathway being a function of electronicsubstituenteffects and the absence or presence of tetramethylethylenediamine or hexamethylphosphoramide.
Atmospheric oxygen was used for the first time as an oxidant in metal-catalyzed homocoupling of Grignard reagents. These manganese- or iron-catalyzed reactions are efficient, cheap, and eco-friendly. They are applicable to the large-scale synthesis of symmetrical conjugated compounds.
Palladium-catalyzed cross-coupling reactions of organogold(i) phosphanes with allylic electrophiles
作者:Miguel Peña-López、Miguel Ayán-Varela、Luis A. Sarandeses、José Pérez Sestelo
DOI:10.1039/c2ob06788a
日期:——
as cinnamyl and geranyl halides (bromide, chloride and acetates) under palladium catalysis in THF at 80 °C to afford the α-substitution product with moderate to high yields. When the reaction is performed with a chiral enantiopure secondary acetate, the α-substituted cross-coupling product is obtained with complete inversion of the stereochemistry.
Reaction of phenyl-substituted allyllithiums with tert-alkyl bromides. Remarkable difference in the alkylation regiochemistry between a polar process and the one involving single-electron transfer
Un chemin reactionnel polaire favorise l'attaque au niveau du site phenyl substitue (C-1) tandis qu'un couplage au niveau de l'autre site (C-3) se produit de facon predominante dans le cas d'un mecanisme SET
Un chemin reactnel polaire favourise l'attaque au niveau du site phenyl substitue (C-1) tandis qu'un couplage au niveau de l'autre site (C-3) se produit de facon predominante dans le cas d'un mecanisme SET