Ru-catalyzed stereoselective addition of imides to alkynes

A catalyst system formed in situ from bis(2-methylallyl)cycloocta-1,5-dieneruthenium(II) ((cod)Ru[met]2), a phosphine, and scandium(III) trifluoromethanesulfonate (Sc(OTf)3) was found to efficiently catalyze the anti-Markovnikov addition of imides to terminal alkynes, allowing mild and atom-economic synthesis of enimides. Depending on the phosphine employed, both the (E)- and the (Z)-isomer can be accessed stereoselectively.     

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.     

Rhodium-catalyzed selective anti-Markovnikov addition of carboxylic acids to alkynes

The selective intermolecular anti-Markovnikov addition of carboxylic acids to terminal alkynes yielding valuable Z-enol esters has been achieved for the first time under rhodium-catalyzed conditions. The catalyst system is applicable to a broad substrate scope and displays a wide functional group tolerance.     

One-pot synthesis of homoallylic ketones from the addition of vinyl grignard reagent to carboxylic esters

Fifteen homoallylic ketones have been synthesized in 26-77% yields on treatment of aromatic, aliphatic, and alpha-amino methyl carboxylates with excess vinylmagnesium bromide and catalytic amounts of a copper salt in THF. Alpha-amino homoallylic ketones derived from N-protected alpha-amino esters possessing aliphatic and alcohol side chains were synthesized in > or =98% enantiomeric purity. [reaction: see text]     

Synthesis of vinyl esters of organosilicon carboxylic acids

Conclusions The vinylation of -silicon-containing carboxylic acids by acetylene under the influence of zinc and cadmium salts was investigated. A method was found for producing organosilicon complex vinyl esters.     

Ruthenium-catalyzed oxidative cleavage of alkynes to carboxylic acids

We describe an efficient method for the oxidative cleavage of alkynes to carboxylic acids using a combination of RuO(2)/Oxone/NaHCO(3) in a CH(3)CN/H(2)O/EtOAc solvent system. Both internal and terminal alkynes, regardless of their electron density, can be oxidized to carboxylic acids in excellent yield (up to 99%). (1)H NMR spectroscopy and ESI-MS experiments provided evidence for alpha-diketones and anhydrides as possible intermediates in these oxidation reactions.     

Ruthenium complex catalyzed selective addition of carboxylic acids to acetylenes giving enol esters

Carboxylic acids react with acetylenes in the presence of a catalytic amount of bis(η⁵-cyclooctadienyl)ruthenium-PR₃-maleic anhydride in toluene to give enol esters in good to excellent yields with high regioselectivity.     

Redox-neutral atom-economic rhodium-catalyzed coupling of terminal alkynes with carboxylic acids toward branched allylic esters

A new method for the preparation of a wide range of branched allylic esters from terminal alkynes that proceeds via a redox-neutral propargylic CH activation employing a rhodium(I)/DPEphos catalyst is reported.     

Accelerated microdroplet synthesis of benzimidazoles by nucleophilic addition to protonated carboxylic acids

We report a metal-free novel route for the accelerated synthesis of benzimidazole and its derivatives in the ambient atmosphere. The synthetic procedure involves 1,2-aromatic diamines and alkyl or aryl carboxylic acids reacting in electrostatically charged microdroplets generated using a nano-electrospray (nESI) ion source. The reactions are accelerated by orders of magnitude in comparison to the bulk. No other acid, base or catalyst is used. Online analysis of the microdroplet accelerated reaction products is performed by mass spectrometry. We provide evidence for an acid catalyzed reaction mechanism based on identification of the intermediate arylamides. Their dehydration to give benzimidazoles occurs in a subsequent thermally enhanced step. It is suggested that the extraordinary acidity at the droplet surface allows the carboxylic acid to function as a C-centered electrophile. Comparisons of this methodology with data from thin film and bulk synthesis lead to the proposal of three key steps in the reaction: (i) formation of an unusual reagent (protonated carboxylic acid) because of the extraordinary conditions at the droplet interface, (ii) accelerated bimolecular reaction because of limited solvation at the interface and (iii) thermally assisted elimination of water. Eleven examples are shown as evidence of the scope of this chemistry. The accelerated synthesis has been scaled-up to establish the substituent-dependence and to isolate products for NMR characterization.

We report a metal-free novel route for the accelerated synthesis of benzimidazole and its derivatives in the ambient atmosphere.     

Phase-transfer catalyzed synthesis of 2-propenyl esters of carboxylic acids

Summary The tetrabutylammonium bromide catalyzed esterification of salts of carboxylic acids1 a–e with 2-propenyl halides2 a,b is described.

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Phasentransferkatalysierte Synthese von 2-Propenylestern von Carbonsäuren (Kurze Mitt.)

Zusammenfassung Es wird die tetrabutylammoniumkatalysierte Veresterung von Carbonsäuresalzen1 a–e mit 2-propenylhalogeniden2 a,b beschrieben

     

Ruthenium-catalyzed regio- and stereoselective addition of carboxylic acids to aryl and trifluoromethyl group substituted unsymmetrical internal alkynes

The regio- and stereoselective addition of carboxylic acids to aryl and trifluoromethyl group substituted unsymmetrical internal alkynes has been accomplished: the Ru(3)(CO)(12)/3PPh(3) catalyst system has effectively catalyzed the reaction to afford the trifluoromethyl group substituted (E)-enol esters with high regio- and stereoselectivities.     

Regiocontrolled addition of arylboronic acids to allenes using palladium and platinum catalysts

Studies about the regiocontrolled addition of arylboronic acids to allenes using a palladium or a platinum catalyst have been described. The selectivity of the reaction can be altered by the choice of the metal reagent and base. Contrary to the formation of endo-olefinic products in the reactions using hydroxopalladium complex, predominant production of exo-olefinic products was observed by the reaction with hydroxoplatinum complex.     

Metal-free synthesis of aryl esters from carboxylic acids and diaryliodonium salts

An efficient arylation of carboxylic acids with diaryliodonium salts has been developed, giving aryl esters in high yields within short reaction times for both aromatic and aliphatic substrates. The transition-metal-free conditions are compatible with a range of functional groups, and good chemoselectivity is observed with unsymmetric diaryliodonium salts. Furthermore, steric hindrance in the ortho positions is well tolerated both in the carboxylic acid and in the diaryliodonium salt, yielding aryl esters that cannot be obtained via other esterification protocols.     

Free-radical addition of aliphatic carboxylic acids to dialkyldiallylsilanes

Summary When reaction is initiated with t-butyl peroxide, carboxylic acids add to one double bond of dialkyldially lsilanes with subsequent homolytic intramolecular cyclization of the intermediately formed free radical with formation of a compound containing a silicon atom in a six-membered ring.     

Metal-free synthesis of aryl esters by coupling aryl carboxylic acids and aryl boronic acids

A facile synthesis of aryl esters is developed by coupling aryl carboxylic acids and aryl boronic acids in the presence of PhI(OAc)₂ and carbonyl diimidazole. A wide range of functional groups were tolerant to the metal-free reaction condition that led to the desired products in good yields.     

Free radical addition of carboxylic esters to unsaturated epoxy compounds

Conclusion The addition of esters to unsaturated epoxy compounds, initiated by di-t-butyl peroxide, forms esters containing an epoxy group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, pp. 2297–2300, October, 1969.     

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.