Asymmetric synthesis of monohydroxy tetradecanoic acids and their methyl esters

Methyl 3-, 6- and 13-oxo tetradecanoates were reduced by NaBH₄ in the presence of 1,2:5,6-di-O-isopropylidene-d-glucofuranose (DIPGH) and (−)-menthol together with isovaleric and pivalic acids in THF solution. The highest enantiomeric purity was found for the 13-hydroxy ester isomer of 96% ee. Enantiomeric excess (ee, %) was determined by chiral HPLC and ¹H NMR with shift reagent, Eu(tfc)₃.     

Reactions of triphenylphosphine with 2,3-dihalo-2-methylpropionic acids and their methyl esters

Triphenylphosphine reacts with 2,3-dichloro-2-methylpropionic acid and its ester along the dehydrochlorination pathway with the participation of the less labile hydrogen atom from the methyl group. The subsequent reaction of the unsaturated product with triphenylphosphine yields 2-carboxypropane- and 2-methoxycarbonylpropane-1,3-diylbis(triphenylphosphonium) dichlorides, respectively. The unusual course of dehydrochlorination may be due to easier electron density transfer from the C-H bond of the methyl group as compared to the chloromethyl group in the carbocationoid intermediate. With the bromine analogs, the reaction pathways are different. The ester reacts similarly to dibromopropionic acid and its derivatives, following the debromination scheme, whereas the free acid gives the product of double nucleophilic substitution.     

Plant-polyphenols and related compounds. A mass-spectrometric study of the trimethylsilyl derivatives of hydroxy- and/or methoxy-substituted cinnamic acids and of their methyl esters

The low resolution 70 eV mass spectra of the TMS (Trimethylsilyl) derivatives of eight naturally occurring hydroxy- and/or methoxycinnamic acids are presented in detail. The TMS derivatives studied are I, of o-coumaric acid; II, of m-coumaric acid; III, of p-coumaric acid; IV, of isoferulic acid; V, of ferulic acid; VI, of 3,4-dimethoxycinnamic acid; VII, of sinapic acid; VIII, of caffeic acid; Ia to Va, VIIa, of the corresponding methyl esters; and VIa, methyl 3,4-dimethoxycinnamate. The derivatives studied show a high degree of stability under conditions of electron-impact. The major fragmentation processes for the free acid TMS derivatives begin with methyl radical loss from either the ester or ring TMS group. The spectra of the methyl ester TMS derivatives have enabled the site of initial methyl loss to be determined. Accurate mass measurements and analysis of the second field-free region metastable peaks provide support for suggested fragmentation schemes. The spectra are sufficiently different to permit identification except between compounds IV and V (and IVa and Va) where the major fragmentation process involves a common ion, thought to be the silicon analogue of an acetonide.     

Electrocatalytic haloform reaction - conversion of methyl ketones to methyl esters of carboxylic acids

An electrocatalytic haloform reaction is accomplished. Methyl ketones are converted to the corresponding carboxylic acid methyl esters in a diaphragmless electrolyzer in methanol in the presence of catalytic quantities of NaBr. The methyl ester of 3-phenylpropanoic acid is formed from benzyl methyl ketone under these conditions via electrochemically induced Favorskii rearrangement.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 122–126, January, 1991.     

Resonant electron capture by some amino acids and their methyl esters

Resonant electron capture mass spectra of aliphatic and aromatic amino acids and their methyl esters show intense [M-H](-) negative ions in the low-energy range. Ion formation results from a predissociation mechanism mediated by the low-energy pi*oo resonant state. Methylation in general has little influence on the electronic structure according to quantum chemical calculations, but the corresponding ions from the methyl esters, [M-Me](-), could be ascertained to arise only at higher resonance energies. Aromatic amino acids are characterized by an additional low-energy fragmentation channel associated with the generation of negative ions with loss of the side chain. The complementary negative ions of the side chains are more efficiently produced at higher energies. The results have significant implications in biological systems as they suggest that amino acids can serve as radiation protectors since they have been found to efficiently thermalize electrons.     

Dissociative electron-capture mass spectrometry of fatty acids and their pyrrolidies and methyl esters

The regions of the energies of resonance capture of electrons by the molecules of fatty acids and their pyrrolidides and methyl esters have been established, which has permitted an explanation of the difference between the dissociative electron-capture mass spectra of these compounds and their chemical ionization and fast-atom bombardment negative-ion mass spectra. It has been shown that the dissociative electron-capture mass spectra of a high-energy resonance state characterized by the most far-reaching dissociation permit the unambiguous determination of the positions of multiple bonds in the initial molecules.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR. Translated from Khimiya Priordnykh Soedinenii, No. 3, pp. 348–353, May–June, 1987.     

Kinetics of the reaction of methyl radical with hydroxyl radical and methanol decomposition

The CH3 + OH bimolecular reaction and the dissociation of methanol are studied theoretically at conditions relevant to combustion chemistry. Kinetics for the CH3 + OH barrierless association reaction and for the H + CH2OH and H + CH3O product channels are determined in the high-pressure limit using variable reaction coordinate transition state theory and multireference electronic structure calculations to evaluate the fragment interaction energies. The CH3 + OH --> 3CH2 + H2O abstraction reaction and the H2 + HCOH and H2 + H2CO product channels feature localized dynamical bottlenecks and are treated using variational transition state theory and QCISD(T) energies extrapolated to the complete basis set limit. The 1CH2 + H2O product channel has two dynamical regimes, featuring both an inner saddle point and an outer barrierless region, and it is shown that a microcanonical two-state model is necessary to properly describe the association rate for this reaction over a broad temperature range. Experimental channel energies for the methanol system are reevaluated using the Active Thermochemical Tables (ATcT) approach. Pressure dependent, phenomenological rate coefficients for the CH3 + OH bimolecular reaction and for methanol decomposition are determined via master equation simulations. The predicted results agree well with experimental results, including those from a companion high-temperature shock tube determination for the decomposition of methanol.     

Reactions of methyl esters of adamantane acids with acetonitrile

Russian Chemical Bulletin - Methyl adamantane-1-carboxylate and methyl (1-adamantyl)acetate react with acetonitrile in the presence of sodium hydride to give 3-(1-adamantyl)-3-oxopropanenitrile and...     

The reaction of amidoximes with carboxylic acids or their esters under high-pressure conditions

Russian Chemical Bulletin - 3,5-Disubstituted 1,2,4-oxadiazoles were synthesized by the reaction of amidoximes with carboxylic acids or their esters under high-pressure conditions (10 kbar). The...     

Preparation of Au/TiO2 nanocomposites and their catalytic activity for DPPH radical scavenging reaction

Au/TiO2 nanocomposites have been prepared by UV photolysis or chemical reduction of a Au(III) complex formed on a spherical or a rodlike TiO2 support, and their catalytic activity for 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging reaction was investigated. The chemical reduction with dimethylamine borane (DMAB) provided smaller gold nanoparticles than those synthesized by UV photolysis. Type of the TiO2 also affected the size of gold particles; smaller gold particles were deposited on the spherical TiO2 support than on rodlike one. For the radical scavenging reaction, the Au/TiO2 nanocomposites prepared by chemical reduction exhibited a higher catalytic activity than those photochemically prepared, and rodlike TiO2 provided a higher activity than spherical one. The effects of preparation methods and type of TiO2 supports on the catalytic activity are discussed.     

Stereoselection in the Betti reaction of valine methyl esters

The multi-component Betti reaction of 2-naphthol, benzaldehyde and (S)-amines, that usually provides highly valuable aminobenzylnaphthol bearing two stereogenic centers, yielded a completely racemic product, when (S)-valine methyl ester was employed as the amine in the usual reaction protocol. The cause of this drawback, that appears to be overlooked in the literature, was investigated. As a result, new reaction conditions were set up, that were able to yield the expected useful product, having two fully resolved stereogenic centers. Furthermore, when the effect of substituents on the phenyl ring was preliminarily studied, we found that 4-fluoro- and 4-chlorobenzaldeyde gave stereoisomerically pure compounds also in the original reaction protocol.     

Friedel-Crafts alkylation of benzene by normal ω-chloroalkanoic acids and their methyl esters and nitriles

Conclusions In the alkylation of benzene by -chloroalkanoic acids Cl(CH₂)_nCOOH (where n=3–6) and their methyl esters and nitriles, in the presence of A1C1₃, the degree of isomerization of the alkyl chain is less than with the corresponding 1-chloroalkanes, depending on the increase in electron acceptor activity in the sequence HOOC-> CH₃OCO-> CN-.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 367–371, February, 1987.