Palladium-Catalyzed Synthesis of α-Methyl Ketones from Allylic Alcohols and Methanol
One-pot synthesis of α-methyl ketones starting from 1,3-diaryl propenols or 1-aryl propenols and methanol as a C1 source is demonstrated. This one-pot isomerization-methylation is catalyzed by commercially available Pd(OAc)2 with H2O as the only by-product. Mechanistic studies and deuterium labelling experiments indicate the involvement of isomerization of allyl alcohol followed by methylation through a hydrogen-borrowing pathway in these isomerization-methylation reactions.
Iron-Catalyzed Tandem Three-Component Alkylation: Access to α-Methylated Substituted Ketones
The borrowing hydrogen strategy has been applied in the synthesis of α-branched methylated ketones via a tandem three-component reaction catalyzed by a diaminocyclopentadienone iron tricarbonyl complex. Various alkyl and aromatic methyl ketones underwent dialkylation with various primary alcohols and methanol as alkylating agents in mild reaction conditions and good yields. Deuterium labeling experiments suggested that the benzylic alcohol was the hydrogen source in this tandem process.
Syndiotactic Poly(aminostyrene)-Supported Palladium Catalyst for Ketone Methylation with Methanol
Palladium nanoparticles immobilized on an amino-functionalized syndiotactic polystyrene (sPS-N) served as a novel recyclable catalyst for the dimethylation and cross methyl alkylation of a wide range of ketones with methanol as the methylation agent. This heterogeneous catalyst (Pd@sPS-N) was highly robust and showed excellent thermal stability and chemical resistance. It not only showed remarkably high activity, but it could also be easily recovered by filtration without loss of activity.
Utilization of MeOH as a C1 Building Block in Tandem Three-Component Coupling Reaction
Ru(II) catalyzed tandem synthesis of α-branched methylated ketones via multicomponent reactions following the hydrogen borrowing process is described. This nonphosphine-based air and moisture stable catalyst efficiently produced various methylated ketones using methanol as a methylating agent. This system was found to be highly effective in three-component coupling between methanol, primary alcohols, and methyl ketones. A proposed catalytic cycle for the α-methylation is supported by DFT calculations as well as kinetic experiments.
A Convenient Ruthenium-Catalysed α-Methylation of Carbonyl Compounds using Methanol
An efficient ruthenium catalyst is reported, for the first time, to catalyse the α-methylation of ketones and esters using methanol as a green methylating agent. The in situ generated catalyst from the complexes [RuCp*Cl2]2or [RuCp*Cl2]nwith dpePhos provided up to quantitative yields in the presence of only 20 mol% of lithium tert-butoxide (LiO-t-Bu) as a base. Regioselective mono- or multi-methylation could be effectively controlled by temperature. This catalyst system was also effective for the one-pot sequential α-alkylation–α-methylation of methyl ketones and conjugate reduction–α-methylation of α,β-unsaturated ketones to synthesise α-branched ketones. An application of the α-methylation of esters using the ruthenium catalyst was demonstrated for an alternative catalytic synthesis of Ketoprofen. (Figure presented.).
Dang, Tuan Thanh,Seayad, Abdul Majeed
supporting information
p. 3373 - 3380
(2016/11/13)
Iridium-catalyzed selective α-methylation of ketones with methanol
Iridium-catalyzed selective α-dimethylation and α-methylation of ketones or phenylacetonitriles, using methanol as the methylating agent, were achieved. In addition, three-component cross α-methyl-alkylation was successfully performed using methyl ketones with methanol and primary alcohols with long-chain alkyl groups. This method provides a very convenient direct route to α-methylated ketones, using methanol.
Ogawa, Shinji,Obora, Yasushi
supporting information
p. 2491 - 2493
(2014/03/21)
Reaction of 3-Amino-2-alkenimines with Alkali Metals: Unexpected Synthesis of Substituted 4-(Arylamino)quinolines
A study of the reduction of 3-amino-2-alkenimines 1 with alkali metals is reported.The nature of the alkali metal plays an important role in the course of the process.In this context, a new and simple method for the regioselective synthesis of 4-(arylamino)quinolines 4 from 1 and sodium or potassium is described.
Mild and Regiospecific Reduction of Masked 1,3-Dicarbonyl Derivatives to Monocarbonyl Compounds and Primary and Secodary Amines
The regiospecific reduction of masked 1,3-dicarbonyl compounds to the corresponding saturated monocarbonyl 3 or iminic 4 compounds via 3-amino-2-alkenimines 1 is described.The formation of 3 and 4 can be explained in terms of a double reduction process from 1.A simple method for the synthesis of primary and secondary amines 6 is also described.