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...     

Reactions of benzamidoxime and its sodium salt with methyl esters of fluorinated acids

The reactions of benzamidoxime and its sodium salt with methyl esters of fluorinated acids at 20–100°C give 1, 2, 4-oxadiazoles or O-addition products.Translated fromIzvestiya Akademli Nauk. Seriya Khimicheskaya, No. 3, pp. 530–532, March, 1993.     

Reaction of amides of 2,3-dibromopropionic and 2-bromoacrylic acids with pyridine and triphenylphosphine

By refluxing pyridine with 2,3-dibromopropionic acid amide in acetonitrile, amide of 3-bromo-2-pyridiniumbromidopropionic acid I was synthesized. The latter is inert toward the second molecule of pyridine under the used conditions. Compound I was found to react with triphenylphosphine to form a mixture of 3-triphenylphosphoniumbromidopropionitrile II and 1-triphenylphosphoniumbromido-2-pyridiniumbromidoethane III. Schemes of reactions were suggested involving attack of phosphine on the carbonyl group as the first stage. The reaction of α-bromoacrylic acid amide with triphenylphosphine was shown to yield also compound II. Evidently, this reaction proceeds through intermediate formation of enolphosphonium salt.     

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.     

SN2 Reactions with Carboxylic Esters. Selective cleavage of methyl esters

Sodium cyanide in hexamethylphosphoric triamide selectively cleaves methyl esters in the presence of ethyl esters with yields of ca. 80%. The mechanism of the reaction has been investigated. It consists of nucleophilic displacement by cyanide of the carboxylate ion from the alcohol carbon atom (B_Al2 mechanism).     

Mass spectrometry of N-(Pyrimidin-2-yl)amino acids and their methyl esters

N(Pyrimidin-2-yl)-glycine, -alanine and -phenylalanine (1-3) and their methyl esters (4-6) were investigated using electron impact (EI) mass Spectrometry. The results showed that EI-induced decomposition occurs on the carboxylic group or involves the loss of R₂OH. In contrast to earlier investigations on N-(pyrimidin-4-yl)amino acids, elimination of water (in 1-3) or methanol (in 4-6) was found to be of EI-induced nature. The loss of 'COOH from M⁺ of ester 4 suggests the occurrence of a skeletal rearrangement leading to the isomeric N-methylamino acid.     

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.     

Reactions of cyclic boric acids esters with paraformaldehyde

Reactions of five- and six-membered cyclic esters of boric acids with paraformaldehyde lead to the corresponding 1,3-dioxacycloalkanes. It is shown that trans-isomers of 2,4,5-substituted 1,3,2-dioxaborinanes react faster than their cis-isomers.     

Azides of N-substituted aziridine-2-carboxylic acids. Reaction with methyl esters of amino acids

The corresponding azide was obtained by nitrosation of 1-benzylaziridine-2-carboxylic acid hydrazide. Reaction of the azide with methyl esters of amino acids gave N-(1-benzyl-2-aziridinylcarbonyl)-substituted methyl esters of amino acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1350–1352, October, 1980.     

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.     

Reaction of 2-aminopyrimidines with αhalocarboxylic acids and their esters

N-Pyrimidylcarboxylic acids and their esters, which can be cyclized to tetrahydromidazo-[1,2-a]pyrimidine-2,5-diones, are formed from 2-aminopyrimidine and its C-substituted derivatives by reaction with -halo acids and their esters under mild conditions. Alkylation proceeds at the N₁ and N₃ atoms of the pyrimidine ring during the action of unsymmetrical 2-aminopyrimidines with -halo acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1140–1142, August, 1974.     

Reactions of aluminum alkoxides with esters of inorganic acids

Russian Chemical Bulletin -     

Synthesis of 2,3-substituted thienylboronic acids and esters

A noncryogenic protocol for the synthesis of 2-substituted 3-thienylboronic acids and esters as well as 3-substituted 2-thienylboronic acids and esters has been developed. Electrophiles were introduced regiospecifically in the 2-position of 2,3-dibromothiophene and in the 3-position of 2-bromo-3-iodothiophene by halogen-magnesium exchange followed by quenching with electrophiles. Palladium-catalyzed borylation of the 2,3-substituted halothiophenes with pinacolborane and P(t-Bu)3 as ligand for Pd produced 9 and 10. The borylation protocol was tolerated by a range of functional groups; however, strongly electron-withdrawing substituents decreased the stability of the thienylboronic acids and esters.     

Fluorolactonization of norbornenecarboxylic acids and their methyl esters with F-TEDA-BF4 and XeF2

The selective fluorolactonization was achieved by treatment of cis-5-norbornene-2,3-endo-dicarboxylic acid or its monomethyl and dimethyl esters with F-TEDA-BF₄ or XeF₂. The reactions of 5-norbornene-endo-2-carboxylic acid and its monomethyl ester with F-TEDA-BF₄ or XeF₂ proceed in a non-selective manner to give fluorolactonization, addition and rearrangement products. The basic factor responsible for selectivity of the fluorolactonization is the presence of two endo-oriented carboxyl groups in the substrate molecule. The electrophilicity and type of the fluorinating agent is of secondary importance in this regard. It is postulated that the fluorolactonization of norbornenecarboxylic acids and their methyl esters with F-TEDA-BF₄ or XeF₂ is realized mainly via “open” fluoronorbornyl carbocation intermediates which in the reaction with XeF₂ are postulated as the tight ion pairs.     

Reactions of P(III) thiobenzyl esters with methyl iodide

The reactions of S-benzyl diphenylthiophosphinite and 2-benzylthio-4,5-benzo-1,3-dioxaphospholane with methyl iodide have been examined. In contrast to the oxygen analogs, the reaction occurs under mild conditions, and does not give Arbuzov reaction products.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2856–2857, December, 1991.     

Electron-transfer reaction of cinnamic acids and their methyl esters with the DPPH(*) radical in alcoholic solutions

The kinetic behavior of cinnamic acids, their methyl esters, and two catechols 1-10 (ArOH) in the reaction with DPPH(*) in methanol and ethanol is not compatible with a reaction mechanism that involves hydrogen atom abstraction from the hydroxyl group of 1-10 by DPPH(*). The rate of this reaction at 25 degrees C is, in fact, comparatively fast despite that the phenolic OH group of ArOH is hydrogen bonded to solvent molecules. The observed rate constants (k(1)) relative to DPPH(*) + ArOH are 3-5 times larger for the methyl esters than for the corresponding free acids and, for the latter, decrease as their concentration is increased according to the relation k(1) = B/[ArOH](0)(m), where k(1) is given in units of M(-1) s(-1), m is ca. 0.5, and B ranges from 0.02 (p-coumaric acid) to ca. 3.48 (caffeic acid) in methanol and from 0.04 (p-coumaric acid) to ca. 13 (sinapic acid) in ethanol. Apparently, the reaction mechanism of DPPH(*) + ArOH involves a fast electron-transfer process from the phenoxide anion of 1-10 to DPPH(*). Kinetic analysis of the reaction sequence for the free acids leads to an expression for the observed rate constant, k(1), proportional to [ArOH](0)(-1/2) in excellent agreement with the experimental behavior of these phenols. The experimental results are also interpreted in terms of the influence that adventitious acids or bases present in the solvent may have. These impurities dramatically influence the ionization equilibrium of phenols and cause a reduction or an enhancement, respectively, of the measured rate constants.