ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
Subject(s)
Pyridines/chemistry , Ruthenium/chemistry , Sulfinic Acids/chemistry , CatalysisABSTRACT
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.
Subject(s)
Alcohols/chemistry , Amines/chemistry , Iridium/chemistry , Water/chemistry , Alkylation , CatalysisSubject(s)
Amines/chemistry , Hydrogen/chemistry , Iridium/chemistry , Alkylation , Aniline Compounds/chemistry , CatalysisABSTRACT
Transition-metal-catalyzed hydrogen-transfer reactions have been used for the conversion of alcohols into benzimidazoles and aldehydes into benzoxazoles and benzothiazoles.
Subject(s)
Alcohols/chemistry , Aldehydes/chemistry , Benzimidazoles/chemical synthesis , Benzothiazoles/chemical synthesis , Benzoxazoles/chemical synthesis , Benzimidazoles/chemistry , Benzothiazoles/chemistry , Benzoxazoles/chemistry , Catalysis , Combinatorial Chemistry Techniques , Iridium/chemistry , Molecular Structure , Oxidation-Reduction , Ruthenium/chemistryABSTRACT
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.
Subject(s)
Electrons , Halogens/chemistry , Vinyl Compounds/chemistry , Alkenes/chemistry , Ions/chemistry , Ligands , Molecular Structure , Palladium/chemistryABSTRACT
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.