Refernces
10.1021/jo00386a046
The research focuses on the regiospecificity in the alkylation of ester enolates, aiming to synthesize sterically hindered diarylketene acetals. The study explores the alkylation of enolate anions, which can occur on either carbon or oxygen, and how the regiospecificity is influenced by factors such as solvent, temperature, and counterion. The researchers found that the alkylation of enolates of methyl bis-(pentamethylphenyl)acetate and isopropyl bis(pentachlorophenyl)acetate occurs exclusively on oxygen, yielding diarylketene acetals. The extreme steric hindrance of these groups is responsible for the stability of these ketene acetals in acid. The chemicals used in the process include various esters, lithium alkoxide, n-butyllithium, methyl sulfate, and methyl triflate, among others. The conclusions drawn from the study indicate that the introduction of pentasubstituted aryl groups into the α-carbon of an ester leads to exclusive O-alkylation of the ester enolate, and the resulting ketene acetals are highly acid-resistant.
10.1021/om1003607
The research aims to develop a modular synthetic route for a new type of anionic N-heterocyclic carbene (NHC) ligand incorporating an enolate group as a reactive backbone component. This design allows for further tailoring of the ligand's electronic properties even after complexation with transition metals. The study uses key chemicals such as formamidines (Ar-NH-CHdNAr), chloroacetyl chloride, and various electrophiles like pivaloyl chloride, methyl triflate, and triflic anhydride. The researchers also employ transition metals like rhodium and copper in the form of [RhCl(1,5-COD)]2 and CuCl. The purpose is to create NHC ligands with tunable electronic properties through post-functionalization, which can be applied in catalysis. The conclusions show that the electronic properties of the NHC ligands can be effectively modulated over a relatively broad range by adding various electrophiles to the enolate backbone, either at the oxygen or carbon. This provides a versatile method for optimizing catalyst performance in transition metal complex catalyzed reactions.
10.1021/ic802286u
The study focuses on the synthesis, structural characterization, and reactivity of palladium(II) aminodiphosphine PNP pincer complexes, specifically the dialkylamides [PdR(PNP)] (where R is Cl, Me, Ph; PNP is (NCH2CH2PiPr2)2). These complexes were prepared and characterized to understand their role in C-N coupling reactions, which are significant in cross-coupling reactions like the Hartwig-Buchwald process. The chemicals used include palladium(II) salts, KOBu, AgPF6, TlPF6, MeOTf, PMe3, CNtBu, and various solvents like benzene, THF, and pentane. These reagents and solvents serve various purposes such as deprotonation, chloride abstraction, oxidation, and methylation reactions, as well as solvents for reactions and purification steps. The study aims to provide insights into the molecular structures, basicity (pKa values), and reactivity patterns of these complexes, which are crucial for understanding catalytic mechanisms in C-N bond formation. The results indicate that the palladium PNP dialkylamido complexes are stable, feature pyramidal nitrogen atoms, and exhibit reactivity towards electrophiles and oxidizing agents, with the reactivity being influenced by the nature of the ligands and the palladium-nitrogen bonding.
10.1021/ja801574q
The study focuses on the stereoselective synthesis of α-L-Rhamnopyranosides (α-L-Rha), a challenging task due to their structural similarity to α-D-mannopyranosides. The researchers employed a novel intramolecular aglycon delivery (IAD) strategy using 2-naphthylmethyl (NAP) ether to create a temporary linkage between the donor and acceptor as a mixed acetal. This approach was found to be highly effective, yielding α-L-Rhamnosides with high selectivity and good yields. Chemicals used in the study include 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) for the formation of mixed acetals, MeOTf and 2,6-di-tert-butyl-4-methylpyridine (DTBMP) for the IAD reaction, and TMS ether for intramolecular trapping of the benzylic cation. The purpose of these chemicals was to facilitate the synthesis of α-L-Rhamnosides with high stereoselectivity, which is crucial for the construction of complex carbohydrate structures found in various bacterial polysaccharides.
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