Kinetic carbonyl derivatives

Jenner investigated the kinetic pressure effect on some specific Michael and Henry reactions and found that the observed activation volumes of the Michael reaction between nitromethane and methyl vinyl ketone are largely dependent on the magnitude of the electrostriction effect, which is highest in the lanthanide-catalyzed reaction and lowest in the base-catalyzed version. In the latter case, the reverse reaction is insensitive to pressure.52 Recently, Kobayashi and co-workers reported a highly efficient Lewis-acid-catalyzed asymmetric Michael addition in water.53 A variety of unsaturated carbonyl derivatives gave selective Michael additions with a-nitrocycloalkanones in water, at room temperature without any added catalyst or in a very dilute aqueous solution of potassium carbonate (Eq. 10.24).54... 

Withers, H.P., Eliezer, K.F., and Mitchell, J.W. 1990. Slurry-phase Fischer-Tropsch synthesis and kinetic studies over supported cobalt carbonyl derived catalysts. Ind. Eng. Chem. Res. 29 1807-14. 

A summary of representative stereochemically defined metal enolates and their respective kinetic aldol condensations with benzaldehyde is provided in Table 24. Both the metal center and the enolate substituent Ri for the substituted carbonyl derivatives... 

Diastereoselective protonation under kinetic control is a useful strategy for allowing access to particular diastereoisomeric carbonyl derivatives. For example, deprotonation of y-lactone 116 with excess LiHMDS in THF at —78°C, and quenching the resulting lithium enolate with saturated aqueous solution of sodium sulfate, gave the diastereoiso-mericaUy pure y-lactone 116 (equation 27). The diastereoselective protonation of the intermediate hthium enolate with H2O must occur on its less hindered face, controlled by the y-benzyloxymethyl substituent of the y-lactone residue to give the required 116. ... 

A kinetic study of the effect of water on the hydrolysis of (173) established the existence of two reaction pathways leading to the carbonyl derivatives, depending on water concentration. The unsatisfactory results observed in many instances led to modifications of the hydrolysis conditions. The supposed limitation of the Nef reaction due to steric hindrance is probably a result of the low solubility of nitroalkanes in aqueous alkali, as demonstrated by the success of the reaction if THF-H20," alcoholic sodium hydroxide" or alkoxide" is used. Silica gel" ° as a reaction medium is of great advantage when the use of organic solvents is undesirable. A two-layer method represents an improvement for the conversion of aromatic nitroalkanes. ... 

Table 7 Spectral and kinetic data of the fluorescence emissions of carbonyl derivatives (3)—(5) of azulene at 11K...

B.iv. Nitrile Enolates. Nitrile enolates are formed by reaction of a nitrile with LDA or another suitable base. Both alkylation 30 and condensation reactions with aldehydes 3 or ketones are known. 32 in addition to alkyl halides and carbonyl derivatives, condensation can occur with another nitrile. The base-catalyzed condensation of two nitriles to give a cyano-ketone, via an intermediate cyano enolate, is known as the Thorpe reaction. 33.109e Reaction of butanenitrile with sodium ethoxide gave a nitrile enolate, which reacted with a second molecule of butanenitrile at the electrophilic cyano carbon to give 206. Hydrolysis gave an intermediate imine-nitrile (207), which is in equilibrium with the enamine form (208, sec. 9.6.A). Hydrolysis led to the final product of the Thorpe reaction, an a-cyano ketone, 209. 33 Mixed condensations are possible when LDA and kinetic conditions are used to generate the a-lithionitrile (a mixed Thorpe reaction). When pentanenitrile was treated with LDA and condensed with benzonitrile, 2-cyano-l-phenyl-1-pentanone was the isolated product after acid hydrolysis. Nitrile enolates can also be alkylated with a variety of alkyl halides. 34... 

Some kinetic studies involving the reactions of various cobalt carbonyl derivatives with triphenylphosphine have recently been reported. The rate constants were measured for the reactions of a variety of acylcobalt tetra-carbonyl derivatives with triphenylphosphine according to the following equation 237)... 

Seemingly disparate processes promoted by cationic sulfur(IV) species, such as direct ylide transfer to carbonyl derivatives and a sulfoxide-mediated arylation, have been found to have important mechanistic links, revealed through DFT studies and NMR kinetics. ... 

Structure 8.20 is noteworthy because of the high activity of this complex as a precatalyst in alcohol oxidation to the corresponding carbonyl derivative. The chelating ligand in structure 8.21 is a chiral natural product called (-) sparteine. Complex 8.21 also catalyzes oxidations of alcohols. It has been used for kinetic resolution (see Section 8.5.3) of a racemic mixture of a secondary alcohol. 

Conra.d-Limpa.ch-KnorrSynthesis. When a P-keto ester is the carbonyl component of these pathways, two products are possible, and the regiochemistry can be optimized. Aniline reacts with ethyl acetoacetate below 100°C to form 3-anilinocrotonate (14), which is converted to 4-hydroxy-2-methylquinoline [607-67-0] by placing it in a preheated environment at 250°C. If the initial reaction takes place at 160°C, acetoacetanilide (15) forms and can be cyclized with concentrated sulfuric acid to 2-hydroxy-4-methylquinoline [607-66-9] (49). This example of kinetic vs thermodynamic control has been employed in the synthesis of many quinoline derivatives. They are useful as intermediates for the synthesis of chemotherapeutic agents (see Chemotherapeuticsanticancer). 

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