RESUMO
Cyclometalated iridium complexes are shown to be highly efficient and chemoselective catalysts for the transfer hydrogenation of a wide range of carbonyl groups with formic acid in water. Examples include α-substituted ketones (α-ether, α-halo, α-hydroxy, α-amino, α-nitrile or α-ester), α-keto esters, ß-keto esters and α,ß-unsaturated aldehydes. The reduction was carried out at substrate/catalyst ratios of up to 50 000 at pHâ 4.5 and required no organic solvent. The protocol provides a practical, easy and efficient way for the synthesis of ß-functionalised secondary alcohols, such as ß-hydroxyethers, ß-hydroxyamines and ß-hydroxyhalo compounds, which are valuable intermediates in pharmaceutical, fine chemical, perfume and agrochemical synthesis.
RESUMO
A new ferrocenyl oxazaphospholidine oxide 3 was synthesized together with its P-epimer 2 in the reaction of ferrocene lithium with phosphoramidite chloride 1. 3 was successfully derivatized into planar chiral 1,2-ferrocenes, including phosphine ligands, via highly diastereoselective ortho-lithiation and subsequent functionalization; these compounds display opposite planar chirality to those obtained from 2. Some of these 1,2-ferrocenes were further lithiated, allowing for the introduction of a free phosphine group at the oxazaphospholidine ring. The X-ray structures of the compounds 2 and 3 as well as those of the new 1,2-ferrocenes 4 and 7 have been determined.
RESUMO
A selective catalytic meta sulfonation of 2-phenylpyridines was found to occur in the presence of (arene)ruthenium(II) complexes upon reaction with sulfonyl chlorides. The 2-pyridyl group facilitates the formation of a stable Ru-C(aryl) σ bond that induces a strong para-directing effect. Electrophilic aromatic substitution proceeds with the sulfonyl chloride to furnish a sulfone at the position meta to the chelating group. This new catalytic process offers access to atypical regioselectivity for reactions involving chelation-assisted cyclometalation.
Assuntos
Piridinas/química , Rutênio/química , Ácidos Sulfínicos/química , CatáliseRESUMO
Highly regioselective vinylation of electron-rich olefins by bromo- as well as chlorostyrenes is effected by palladium catalysis with either mono- or bidentate phosphines in a molecular solvent, with no need for halide scavengers, ionic liquids, or ionic additives. The use of the hemilabile 1,3-bis(diphenylphosphino)propane monoxide (dpppO) as a ligand led to faster reactions of more challenging 2-substituted vinyl ethers and reduced Pd loadings. In contrast to the related arylation reaction, evidence suggests that the vinylation may proceed via the neutral Heck mechanism.
Assuntos
Elétrons , Halogênios/química , Compostos de Vinila/química , Alcenos/química , Íons/química , Ligantes , Estrutura Molecular , Paládio/químicaRESUMO
A new protocol for the direct acylation of aryl bromides with aldehydes is established. It appears to involve palladium-amine cooperative catalysis, affording synthetically important alkyl aryl ketones in moderate to excellent yields in a straightforward manner, and broadening the scope of metal-catalyzed coupling reactions.
Assuntos
Aldeídos/química , Brometos/química , Paládio/química , Acilação , CatáliseAssuntos
Aminas/química , Hidrogênio/química , Irídio/química , Alquilação , Compostos de Anilina/química , CatáliseRESUMO
Amines have been directly alkylated with alcohols using 1 mol% [Cp*IrI(2)](2) catalyst in water in the absence of base or other additives.
Assuntos
Álcoois/química , Aminas/química , Irídio/química , Água/química , Alquilação , CatáliseRESUMO
Transition-metal-catalyzed hydrogen-transfer reactions have been used for the conversion of alcohols into benzimidazoles and aldehydes into benzoxazoles and benzothiazoles.