Esters Derived from Vanillin and Vanillal and Aromatic and Functionalized Aliphatic Carboxylic Acids

Reactions of vanillin and vanillal with aromatic and functionally substituted aliphatic carboxylic acid chlorides in the presence of pyridine afforded the corresponding previously unknown esters.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1015–1019.Original Russian Text Copyright © 2005 by Dikusar, Kozlov.     

Preparation of Functionalized Esters of Carboxylic Acids

The synthesis of simple esters (methyl, ethyl, etc.) of carboxylic acids is generally a trivial synthetic transformation due to the great variety of mehtods available (CH₂N₂, MeOH-H⁺,Me₂SO₄-Base, copper salts-alkylhalides¹, and CaO with alkylhalides²). However, what was sought in this laboratory were methods for preparation of functionalized esters. Specifically, Investigations are underway to develop methods for intra molecular transfer or intramolecular reaction of the functionalized (“R”) portion of the carboxylic acid ester (as illustrated below).     

Electrophotochemical Metal-Catalyzed Decarboxylative Coupling of Aliphatic Carboxylic Acids

An electrophotochemical dual metal-catalyzed protocol for decarboxylative arylation of simple aliphatic carboxylic acids with aryl halides is reported. The relative stabilities of catalytically active metal complexes simultaneously generated at anode and cathode are the key design elements for the success of this convergent paired electrolysis. This new electrophotocatalytic method is mild, robust, and most importantly, capable of accommodating simple primary aliphatic acids including acetic acid – ubiquitous and variegated structural motifs yet remain oddly challenging substrates – directly as native functional groups for decarboxylative C(sp²)−C(sp³) bond formation.     

Iron-Catalyzed Cleavage Reaction of Keto Acids with Aliphatic Aldehydes for the Synthesis of Ketones and Ketone Esters

The radical–radical coupling reaction is an important synthetic strategy. In this study, the iron-catalyzed radical–radical cross-coupling reaction based on the decarboxylation of keto acids and decarbonylation of aliphatic aldehydes to obtain valuable aryl ketones is reported for the first time. Remarkably, when tertiary aldehydes were used as carbonyl sources, ketone esters were selectively obtained instead of ketones. The gram-scale preparation of aryl ketone through this strategy was easily achieved by using only 3 mol % of the iron catalyst. As a proof-of-concept, the bioactive molecule flurprimidol was synthesized in two steps by using this strategy.     

Ruthenium-Catalysed Cleavage of Alkenes and Alkynes to Carboxylic Acids

Catalysis of alkene and alkyne cleavage to carboxylic acids by ruthenium trichloride in the presence of an excess of periodic acid has been studied in biphasic H₂O - CCl₄-CH₃CN media, and is found to be simple and effective. The active catalyst is shown to be RuO₄.     

Synthesis of D-Mannite Esters of Aliphatic and Aromatic Acids

Mono- and diesters of D-mannite with aliphatic acids and mixed diesters with aliphatic and aromatic acids were synthesized by transesterification of their methyl esters. The structures of the products are confirmed by PMR, ¹³ C NMR, and IR spectra     

Selective Cleavage of Carboxylic Esters in the Presence of Monosubstituted Malonates

Aliphatic carboxylic esters containing in the molecule a malonate moiety with an α-hydrogen undergo selective cleavage in the presence of potassium tertbutoxide in wet tetrahydrofuran.

     

Improved QSAR Analysis of the Toxicity of Aliphatic Carboxylic Acids

The results of a QSPR study of the toxicity of carboxylic acids in aqueous solution are reported. The molecular set comprises 35 carboxylic acids with the corresponding pK _a values in water. The set of molecular and topological parameters includes electrotopological state of the carboxy and methyl groups, molar refractivity, refractive index, n-octanol-water partition coefficient logKo/w, surface tension, and polarizability. Quite reasonable estimates are obtained, which improve the results of previous theoretical calculations.     

Physicochemical Properties of 1,2-Diacylhydrazines Derived from Aliphatic Carboxylic Acids

The solubility and resistance to oxidation and hydrolysis of 1,2-diacylhydrazines derived from acetic, propionic, butyric, and valeric acids were studied in view of possible application of these compounds for concentrating nonferrous metals. The pK ₁ and pK ₂ values of the 1,2-diacylhydrazines were determined. The stability of conformers and the electron density distribution in the coordination-active moiety were estimated by SCF MO LCAO semiempirical calculations in the MNDO-PM3 approximation.     

大环钴(Ⅱ)配合物模拟水解酶催化羧酸酯水解的比较研究

在Brij35胶束溶液中,比较研究了四氮大环席夫碱(5,7,7,12,14,14-六甲基-1,4,8,11-四氮杂十四环-二烯,L)的钴(Ⅱ)配合物1催化对硝基苯酚吡啶甲酸酯(PNPP)及对硝基苯酚乙酸酯(PNPA)水解的动力学。结果表明:配合物1对PNPP及PNPA的催化作用具有酸碱催化的特征,催化活性物种为与金属离子结合的氢氧根离子CoL-OH^-;配合物1催化PNPP水解的速度远远大于其催化PNPA水解的速度,在pH 7.40、30℃时,表观二级速率常数k_c分别为0.997mol^-1·L·s^-1和1.12×10^-3mol^-1·L·s^-1,这种反应速率的差异可归因于反应机理的不同;Brij35胶束对PNPP及PNPA的水解均有抑制作用。     

Vanillin Esters of Aliphatic Acids in the Synthesis of 4,7-Phenanthroline Derivatives

Condensation of vanillin esters of aliphatic acids with 6-aminoquinoline and cyclic c-diketones (1,3-cyclohexanedione and dimedone) afforded new 2-methoxy-4-(11-oxo-7,8,9,10,11,12-hexahydrobenzo[b][4,7]phenanthrolin-12-yl)phenyl esters of carboxylic acids.     

Determination of the Content of Bound Carboxylic Acids in Mixed Cellulose Esters

A method was proposed for differential determination of bound carboxylic acids in mixed cellulose esters containing residues of acetic and higher carboxylic (capric, lauric, myristic, palmitic) acids.     

Oxidation of Alkynyl Boronates to Carboxylic Acids,Esters, and Amides

A general efficient protocol was developed for the synthesis of carboxylic acids, esters, and amides through oxidation of alkynyl boronates, generated directly from terminal alkynes. This protocol represents the first example of C(sp)?B bond oxidation. This approach displays a broad substrate scope, including aryl and alkyl alkynes, and exhibits excellent functional group tolerance. Water, primary and secondary alcohols, and amines are suitable nucleophiles for this transformation. Notably, amino acids and peptides can be used as nucleophiles, providing an efficient method for the synthesis and modification of peptides. The practicability of this methodology was further highlighted by the preparation of pharmaceutical molecules.     

A Novel Synthetic Method for the Preparation of Aliphatic Aldehydes from the Corresponding Carboxylic Acids

A novel synthetic method for the preparation of aliphatic aldehydes from the corresponding carboxylic acids via 1,3‐dimethylbenzimidazolium salts is provided. 1,3‐Dimethylbenzimidazolium salts were rapidly reduced with sodium/ethanol and then hydrolyzed with hydrochloric acid to obtain aliphatic aldehydes, in which the 1,3‐dimethylbenzimidazolium salts can be readily achieved from the corresponding carboxylic acids. The mechanism for the reductive reaction of 1,3‐dimethylbenzimidazolium salts with sodium/ethanol was discussed.     

Silver‐Catalyzed Decarboxylative Trifluoromethylthiolation of Aliphatic Carboxylic Acids in Aqueous Emulsion

A silver‐catalyzed decarboxylative trifluoromethylthiolation of secondary and tertiary carboxylic acids under mild conditions tolerates a wide range of functional groups. The reaction was dramatically accelerated by its performance in an aqueous emulsion, which was formed by the addition of sodium dodecyl sulfate to water. It was proposed that the radical, which was generated from the silver‐catalyzed decarboxylation in the “oil‐in‐water” droplets, could easily react with the trifluoromethylthiolating reagent to form the product.     

Oxidation of Alkynyl Boronates to Carboxylic Acids,Esters, and Amides

A general efficient protocol was developed for the synthesis of carboxylic acids, esters, and amides through oxidation of alkynyl boronates, generated directly from terminal alkynes. This protocol represents the first example of C(sp)−B bond oxidation. This approach displays a broad substrate scope, including aryl and alkyl alkynes, and exhibits excellent functional group tolerance. Water, primary and secondary alcohols, and amines are suitable nucleophiles for this transformation. Notably, amino acids and peptides can be used as nucleophiles, providing an efficient method for the synthesis and modification of peptides. The practicability of this methodology was further highlighted by the preparation of pharmaceutical molecules.