Carbamoylimidazolium salts as diversification reagents: an application to the synthesis of tertiary amides from carboxylic acids

An efficient method for the preparation of tertiary amides from carbamoylimidazolium salts and carboxylic acids is described. The transformation occurs at room temperature and under relatively mild conditions. The carbamoylimidazolium salts are obtained from the reaction of secondary amines with N,N′-carbonyldiimidazole, followed by methylation with methyl iodide. The utility of this reaction was demonstrated in the formation of Weinreb amides and in a short synthesis of fused bicyclic amides. The introduction of this reaction now permits carbamoylimidazolium salts to be utilized in the formation of tertiary amides, ureas, carbamates and thiocarbamates under a single set of conditions.     

Selenoesters in organic synthesis. 1. Conversion of mixed carboxylic acid esters to selenoesters

Conclusions The rules governing the reaction of mixed carboxylic acid esters with dimethylaluminum methyl selenide have been investigated; it was found that the nature of the solvent and the structure of the precursor ester both exert significant effects on the selectivity of selenoester formation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1650–1654, July, 1985.     

Iron-catalysed green synthesis of carboxylic esters by the intermolecular addition of carboxylic acids to alkenes

Iron triflate, in situ-formed from FeCl3 and triflic acid, or FeCl3 and silver triflate efficiently catalyse the intermolecular addition of carboxylic acids to various alkenes to yield carboxylic esters; the reaction is applicable to the synthesis of unstable esters, such as acrylates.     

Complexation and transport of amino acid esters and their salts with synthesised chiral novel aza crown ether derivatives

The syntheses of four aza-15-crown-5 ethers bearing phenyl and phenoxymethyl moieties attached to a stereogenic centre on the crown ring were achieved. Macrocycles have exhibited strong binding ability (K_a = 5364–12,969 M^? 1) and modest enantiomeric discrimination towards the enantiomers of amino acid methyl ester salts by UV titration method in CHCl₃ at 25°C. Computer modelling results supported experimental data providing a detailed understanding of the molecular recognition mode between hosts and guests and the likely binding sites involved. Macrocycles were used for chiral discrimination of amino acids in their zwitterionic forms or as potassium and sodium salts in transport experiments across a bulk chloroform membrane with satisfactory selectivity.     

Rh-catalyzed asymmetric hydrogenation of gamma-phthalimido-substituted alpha,beta-unsaturated carboxylic acid esters: an efficient enantioselective synthesis of beta-aryl-gamma-amino acids

A series of chiral beta-aryl-gamma-amino acid ester derivatives were synthesized in high enantioselectivities (93-97% ee) via the Rh-catalyzed asymmetric hydrogenation of gamma-phthalimido-alpha,beta-unsaturated carboxylic acid esters using highly modular chiral BoPhoz-type phosphine-aminophosphine ligands. The method has been applied successfully to the synthesis of several chiral pharmaceuticals including (R)-baclofen and (R)-rolipram with high enantioselectivities.     

Phosphorus in organic synthesis—XI Amino acids and peptides—XXI : Reaction of diethyl phosphorocyanidate(DEPC) with carboxylic acids. A new synthesis of carboxylic esters and amides

Diethyl phosphorocyanidate(DEPC) reacts with carboxylic acids in the presence of triethylamine leading to transient formation of acyl cyanides, but in presence of alcohols or amines, carboxylic esters or amides are produced. DEPC is especially effective for the synthesis of amides and peptides, and showed a satisfactory result on the Young racemization test.     

Vibrational spectra of some tetraalkylammonium acid salts of acetic acids. Hydrogen bonding in solids and solutions

Infrared and Raman spectra are reported of several hydrogen dicarboxylates of the composition MH(D)X₂ (M = tetramethyl or tetrabutylammonium, X = CH₃COO, CF₃COO, CCl₃COO) as solids and solutions in nonaqueous solvents. It is shown that very strong hydrogen bonding persists in solution although in some cases the high symmetry observed in the solid is lost by dissolution of melting. The hydrogen diacetate anion appears to have different conformations in the solid and solution. Calculations in the ab-initio scheme (STO-3G) for the trans and cis forms of this ion, without and with countercharges, demonstrate that the cis conformation is more stable in the latter case whereas the trans conformation is preferred without charges.     

Enzymatic esterification of saturated fatty acids with aliphatic alcohols as an alternative method of a low-temperature synthesis of esters

Russian Chemical Bulletin - low-temperature synthesis of saturated fatty acid esters with aliphatic alcohols by enzymatic esterification in the presence of heterogeneous biоcatalysts was...     

Application of ultrasound to organic reactions: ultrasonic catalysis on hydrolysis of carboxylic acid esters

Irradiation with ultrasound was found to facilitate the two-phase basic hydrolysis of aromatic carboxylic acid esters.     

Ti-crossed-Claisen condensation between carboxylic esters and acid chlorides or acids: a highly selective and general method for the preparation of various beta-keto esters

Ti-crossed-Claisen condensation between a 1:1 mixture of carboxylic esters and acid chlorides promoted by TiCl4-Bu3N-N-methylimidazole proceeded successfully to give various beta-keto esters in good yields with excellent selectivities (19 examples, approximately 48-95% yield; cross/self-selectivity = approximately 96/4-99/1). The present method was extended to the condensation between a 1:1 mixture of carboxylic acids and carboxylic esters (six examples, approximately 70-92% yield; cross/self-selectivity = approximately 91/9-99/1). To demonstrate the utility of the present two Ti-crossed-Claisen condensations, we performed a couple of efficient short-step syntheses of two natural, representative, and useful perfumes, cis-jasmone and (R)-muscone.     

Regiocontrolled Ru-catalyzed addition of carboxylic acids to alkynes: practical protocols for the synthesis of vinyl esters

The catalytic activity of commercially available, air and water stable ruthenium complexes in the addition of carboxylic acids to terminal alkynes was found to be drastically enhanced by the addition of small quantities of base. Moreover, the regioselectivity of the reaction can be controlled by the choice of the base so that both the Markovnikov (Na2CO3) and the anti-Markovnikov products (DMAP) are now easily accessible in excellent selectivities.     

Advances in the synthesis of aromatic and heteroaromatic carboxylic acids and their esters

Modern approaches to the synthesis of aromatic and heteroaromatic carboxylic acids and their esters based on the latest advances in organic chemistry are compiled and systematized in this review.     

A selective method for the preparation of aliphatic methyl esters in the presence of aromatic carboxylic acids

2,2-Dimethoxypropane, methanol and a catalytic amount of HCl selectively esterify aliphatic carboxylic acids, in the presence of aromatic carboxylic acids, at room temperature and in high yields.     

氟阴离子在有机合成中的应用 I: 无水氟化钾催化丙二酸二乙酯与苯甲醛的Knoevenagel缩合反应

研究了用无水氟化钾催化苯甲醛与丙二酸二乙酯的Knoevenagel反应的反应条件,发现在适宜条件下可进行这一反应, 并制得予其产物苯甲叉丙二酸二乙酯.