Alkyl-substituted esters

The slower rate of hydrolysis of alkyl substituted esters in the presence of the cation exchange resin can be explained by the assumption that the alkyl groups interfere more in the formation of the intermediate complex on the resin surface than in the homogeneous system. The efficiency of the resin q was less than unity... 

Hata, T., Nakajima, M., and Sekine, M., Facile synthesis of fS-alkyl-substituted esters from a, 3-unsaturated aldehydes, Tetrahedron Lett., 2047, 1979. 

The sodium derivative of acetoacetic ester, prepared by treating the ester with an alcoholic solution of sodium ethylate, is converted into an alkyl substituted ester by boiling with any alkyl iodide ... 

Membranes and other organic barriers are permeable only to compounds of an effective diameter < 9.5 A (Opperhuizen et al, 1985). Larger molecules are hindered to diffuse through membranes and, unless active transport mechanisms act, they cannot reach intracellular targets. To be able to react with specific binding sites (e.g. receptors) the xenobiotic has to have a complementary constitution the lesser the degree of fit the lesser the intrinsic activity. Bulky substituents near reactive centres in a molecule may shield this moiety and thus reduce its reactivity for example, c -alkyl substituted esters are less likely to hydrolyse than analogous compounds with a different substitution pattern. 

Alkyl sulfonate esters resemble alkyl halides m their ability to undergo ehmma tion and nucleophilic substitution... 

Medium reactivity contaminants alcohols, ketones, organic acids, esters, alkyl-substituted aromatics, nitro-substituted aromatics, carbohydrates. 

During electrochemical fluorination retention of important functional groups or atoms in molecules is essential. Acyl fluorides and chlorides, but not carboxylic acids and anhydrides (which decarboxylate), survive perfluorination to the perfluorinated acid fluorides, albeit with some cyclization in longer chain (>C4) species [73]. Electrochemical fluorination of acetyl fluoride produces perfluoro-acetyl fluoride in 36-45% yields [85]. Electrochemical fluorination of octanoyl chloride results in perfluorinated cyclic ethers as well as perfluorinated octanoyl fluonde. Cyclization decreases as initial substrate concentration increases and has been linked to hydrogen-bonded onium polycations [73]. Cyclization is a common phenomenon involving longer (>C4) and branched chains. a-Alkyl-substituted carboxylic acid chlorides, fluorides, and methyl esters produce both the perfluorinated cyclic five- and six-membered ring ethers as well as the perfluorinated acid... 

Disubstituted and trisubstituted isoxazoles are generally stable to alcoholic and aqueous alkali. Such stability of the ring is characteristic both of alkyl-substituted compounds and of the esters, nitriles, etc., of isoxazole carboxylic acids,for example (127 ->128). 

Using an Alkylation Reaction to Prepare a Substituted Ester... 

Tabic 1.3 Relative Rate Constants for Reactions of Radicals with Alkyl-Substituted Acrylate Esters CHR CFEcOaCHs"... 

The kinetics of the sulphuric acid-catalysed decarboxylation of a range of alkyl substituted benzoic acids have been measured by Schubert et a/.634,635. The variation of rate coefficient with temperature for mesitoic acid is given in Table 206 and the value for the methyl ester shows that, at this acid concentration, the... 

Because esters 745 a, b of imidazole-acetic acid are unstable when stored for long periods, owing to intramolecular catalysis by the imidazole moiety, the esters should be converted into their salts or free acids and stored as such. Only tert-butyl imidazole-(4,5)acetates derived from tert-butyl 4-chloroacetoacetate seem to be stable [232, 233]. N-alkyl-substituted amidines give rise to a mixture of alkyl N-alkylimidazole-4- and 5-acetates [232, 233]. 

Aryldioxophosphoranes such as aryl- and alkyl-iminooxophosphoranes number among the short-lived metaphosphonates. The former are best obtained by fragmentation of cyclic phosphinic esters, and the latter by rearrangement of aryl- and alkyl-substituted phosphoryl azides and nitrenes, respectively. This reaction is reminiscent of the phosphorylcarbene/methyleneoxophosphorane rearrangement discussed in Section 2. 

The reaction of cyclohexaamylose with a series of p-carboxyphenyl esters is an example of a decelerating effect which may be clearly attributed to nonproductive binding. Rate effects imposed by cyclohexaamylose on the hydrolyses of three such esters are summarized in Table IX. As the hydrophobicity of the ester function is increased by alkyl substitution, the hydrolysis is inhibited the stability of the inclusion complex, on the other... 

The reaction tolerated a variety of functionality, including ester and ether groups on the alkyl-substituted alkene at least two carbons away from the double bond, and raefa-nitro or para-methoxy substituents on the styrene. As expected, cross-metathesis occurred selectively at the less hindered monosubsti-tuted double bond of dienes also containing a disubstituted alkene (Eq. 8). 

Silicone polymers which were developed in 1930s became commercially important during and after the World War II. The starting material for producing silicone polymers are alkyl chlorosilanes, arychlorosilanes or substituted esters of ortho-silicic acid. 

Comparable selectivities have been published for the intramolecular competition of an ester- and an alkyl-substituted alkyne [89] or a silyl- and an alkyl-substituted alkyne [90],... 

In the late 1960s, methods were developed for the synthesis of alkylated ketones, esters, and amides via the reaction of trialkyl-boranes with a-diazocarbonyl compounds (50,51), halogen-substituted enolates (52), and sulfur ylids (53) (eqs. [33]-[35]). Only one study has addressed the stereochemical aspects of these reactions in detail. Masamune (54) reported that diazoketones 56 (Ri = CH3, CH2Ph, Ph), upon reaction with tributylborane, afford almost exclusively the ( )-enolate, in qualitative agreement with an earlier report by Pasto (55). It was also found that E) - (Z)-enolate isomerization could be accomplished with a catalytic amount of lithium phenoxide (CgHg, 16 hr, 22°C) (54). 

Addition to linear 1,1-disubstituted allylic acetates is slower than addition to monosubstituted allylic esters. Additions to allylic trifluoroacetates or phosphates are faster than additions to allylic carbonates or acetates, and reactions of branched allylic esters are faster than additions to linear allylic esters. Aryl-, vinyl, alkynyl, and alkyl-substituted allylic esters readily undergo allylic substitution. Amines and stabilized enolates both react with these electrophiles in the presence of the catalyst generated from an iridium precursor and triphenylphosphite. 

Acetone cyanohydrin nitrate, a reagent prepared from the nitration of acetone cyanohydrin with acetic anhydride-nitric acid, has been used for the alkaline nitration of alkyl-substituted malonate esters. In these reactions sodium hydride is used to form the carbanions of the malonate esters, which on reaction with acetone cyanohydrin nitrate form the corresponding nitromalonates. The use of a 100 % excess of sodium hydride in these reactions causes the nitromalonates to decompose by decarboxylation to the corresponding a-nitroesters. Alkyl-substituted acetoacetic acid esters behave in a similar way and have been used to synthesize a-nitroesters. Yields of a-nitroesters from both methods average 50-55 %. 

---