Alkyl Trifluoroacetates Research Articles

Selective Photo‐Oxygenation of Light Alkanes Using Iodine Oxides and Chloride

AbstractPartial oxidation of light alkanes to generate alkyl esters has been achieved under photochemical conditions using mixtures of iodine oxides and chloride salts in trifluoroacetic acid (HTFA). The reactions are catalytic in chloride and are successful using compact fluorescent light, but higher yields are obtained using a mercury lamp. In this photo‐initiated oxyesterification process, the robust alkyl ester products are resistant to over‐oxidation, and under optimized conditions yields for alkyl ester production of ∼50 % based on methane, ∼60 % based on ethane (with a total functionalized yield of EtX (X=TFA or Cl) of 80 %) and ∼30 % based on propane have been demonstrated. The reaction also proceeds in aqueous HTFA and dichloroacetic acid with lower yields. Mechanistic studies indicate that the process likely operates by a chlorine hydrogen atom abstraction pathway wherein alkyl radicals are generated, trapped by iodine, and converted to alkyl trifluoroacetates in situ.

Mg–Cu bimetal system for selective C[sbnd]F bond activation

Bimetal system of Mg–CuCl in DMI for selective CF and CCl bonds activation has been examined. This article involves (1) a short overview of bimetal system of Mg-metals for selective CF bond activation, (2) CF bond activation of alkyl trifluoroacetates leading to alkyl difluoro(trimethylsilyl)acetates via difluoroketene silyl acetal, (3) selective CCl bond activation of 3- and 4-chloropentafluoroethylbenzenes, (4) CF bond activation of substituted benzotrifluorides and (5) microscopic observation of an active site of magnesium surface formed in Mg–CuCl system and elucidation of reaction mechanism of CCl and CF bond activation at the active site.

Defluorination–silylation of alkyl trifluoroacetates to 2,2-difluoro-2-(trimethylsilyl)acetates by copper-deposited magnesium and trimethylsilyl chloride

Reductive defluorination–silylation of alkyl trifluoroacetates with copper-deposited magnesium and trimethylsilyl chloride (TMS-Cl) gave 2,2-difluoro-2-(trimethylsilyl)acetates, potential difluoromethylene building blocks, in 60–68% yields.

Facile synthesis of α,α-difluoroalkyl aryl thioethers and their oxidative desulfurization–fluorination to trifluorides

Alkyl 2-arylthio-2,2-difluoroacetates are synthesized in 52–77% yield from alkyl 2-(arylthio)acetates via two succeeding fluoro-Pummerer rearrangements using the reagents combination of N-haloimides as electrophiles and excess Py·9HF as the fluoride source at room temperature. Subsequent treatment of the formed fluorinated thioethers with the same reagents at elevated temperature gave alkyl trifluoroacetates in almost quantitative yield under optimised conditions by oxidative desulfurization–fluorination.

Nickel-catalyzed, sodium iodide-promoted reductive dimerization of alkyl halides, alkyl pseudohalides, and allylic acetates

The first general method for the reductive dimerization of alkyl halides, alkyl mesylates, alkyl trifluoroacetates, and allylic acetates is reported which proceeds with low catalyst loading (0.5 to 5 mol%), generally high yields (80% ave yield), and good functional-group tolerance.

Trifluoroacetic Acid Derivatives as Nucleophilic Trifluoromethylating Reagents.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Trifluoroacetic Acid Derivatives as Nucleophilic Trifluoromethylating Reagents

Secondary trifluoroacetamides and alkyl trifluoroacetates can be used as nucleophilic trifluoromethylating reagents towards non-enolizable ketones by action of potassium tert-butoxide.

CaCl2-Catalyzed Functionalization of Saturated Hydrocarbons with CO to Carboxylic Acids and Esters

The functionalization of saturated hydrocarbons such as ethane, propane, cyclopentane, cyclohexane, cycloheptane, and cyclooctane with CO by CaCl2 catalyst in the presence of K2S2O8 and CF3COOH was studied. In this reaction carboxylic acids were formed as dominant products and alkyl trifluoroacetates were formed as by-products. In the reaction of propane, isobutyric acid was the main product and n-butyric acid and isopropyl trifluoroacetate were the by-products in 95% total yield based on propane when 1 bar of propane reacted with 30 bar of CO in the presence of CaCl2 (0.5 mmol), K2S2O8 (5 mmol), and CF3COOH (5 ml) at 80°C for 24 h. Ethane gave about 88% total yield; however, in that case 23% acetic acid was formed by the oxidation of ethane. Cyclopentane, cyclohexane, and cycloheptane underwent reaction, giving about 44, 33, and 12% total yields, respectively. However, cyclooctane did not undergo this reaction. The activation parameters for the reaction of propane (5 bar) with CO (30 bar) have been determined to be Ea=130.3, 138.0, and 153.8 kJ/mol; A=7.14×1013, 5.83×1014, and 5.80×1016 s−1; ΔH‡=128.0, 134.7, and 150.5 kJ/mol; ΔS‡=10.3, 28.6, and 66.8 J/mol K; and ΔG353‡=124.4, 123.9, and 126.9 kJ/mol for the products isobutyric acid, n-butyric acid, and isopropyl trifluoroacetate, respectively.

One-step carboxylation reaction of saturated hydrocarbons with CO by Co(OAc) 2 catalyst under mild conditions

Direct carboxylation reaction of saturated hydrocarbons with carbon monoxide to afford the corresponding carboxylic acids has been investigated in the presence of cobalt catalysts such as Co(OAc) 2 and K 2S 2O 8 in CF 3COOH (TFA). Alkyl trifluoroacetates were also formed in this reaction in different quantities, depending on the reaction conditions. Methane and ethane gave very low yields of the corresponding carboxylic acids only. The conversion of propane is about 89.5% (based on propane) when 1 bar (0.76 mmol) of propane reacted with 30 bar of carbon monoxide in the presence of 0.1 mmol of Co(OAc) 2 and 10 mmol of K 2S 2O 8 in 5 ml of TFA at 70°C for 15 h. In this reaction, iso-butyric acid is the major product and n-butyric acid and iso-propyl trifluoroacetate are the by-products. The maximum selectivity of iso-butyric acid obtained in this reaction is 62%. Cyclopentane and cyclohexane underwent this reaction under the same reaction conditions; the carboxylated product of cyclopentane is the minor product but, in the case of cyclohexane the carboxylated product is the major one. On the other hand, cycloheptane did not undergo the carboxylation reaction. The activation energies of the reaction of propane (7 bar) with carbon monoxide (30 bar) in the presence of Co(OAc) 2 (0.1 mmol), K 2S 2O 8(10 mmol) and TFA (5 ml) for 3 h at the temperature range of 65–80°C have been determined to be 9.7, 13.4 and 20.3 kcal/mol for the formation of iso- and n-butyric acids and iso-propyl trifluoroacetate, respectively.

Mg/K2S2O8-promoted direct carboxylation of saturated hydrocarbons with CO

Saturated hydrocarbons react with carbon monoxide in the presence of magnesium powder and potassium peroxodisulfate in trifluoroacetic acid (TFA) to afford the corresponding carboxylic acids as major products and alkyl trifluoroacetates as minor products in high yields. The use of equimolar amounts of magnesium (5 mmol) and K2S2O8(5 mmol) is best for this reaction. Cyclohexane is carboxylated most effectively at 80 °C for 30 h using 50 atm CO, 3 ml of TFA and 1 mmol of cyclohexane, giving 80% conversion (95% conversion yield) based on cyclohexane. The reactivity of various saturated hydrocarbons has been determined by competitive reactions of equimolar amounts of cyclohexane (5 mmol) and another hydrocarbon (5 mmol). The order of decreasing reactivity obtained is cycloheptane > cyclohexane > cyclopentane > n-propane > methane. Copyright ­© 1999 John Wiley & Sons, Ltd.

Synthesis of Carboxylic Acids through the Formation of C–C Bond between Saturated Hydrocarbons and CO in the Presence of Mg/K2S2O8/TFA System

Abstract Magnesium powder (Mg) promoted the carboxylation reaction of saturated hydrocarbons with carbon monoxide (CO) in the presence of potassium peroxodisulfate (K2S2O8) in trifluoroacetic acid (TFA) to yield the corresponding carboxylic acids and alkyl trifluoroacetates. About 80% conversion of cyclohexane was achieved when 5 mmol of magnesium, 5 mmol of potassium peroxodisulfate, 3 mL of TFA, 1 mmol of cyclohexane, 50 atm of CO were used at 80 °C for 30 h.

Ruthenium-catalyzed oxidation of alkanes with peracids

The ruthenium-catalyzed oxidation of alkanes with peracids under mild conditions gives the corresponding ketones and alcohols highly efficiently. Similar treatment of alkanes in trifluoroacetic acid gives alkyl trifluoroacetates.

Selective rhodium-catalysed oxidation of alkanes to alkyl esters with peracids

Saturated hydrocarbons are selectively transformed into the corresponding alkyl trifluoroacetates in good yields by treatment with hydrogen peroxide in trifluoroacetic acid in the presence of Rh salts at room temperature.

Gas-phase reactions of certain nucleophiles with alkyl trifluoroacetates. A new probe to distinguish between SN2 and E2 mechanisms for alkyl derivatives

Gas-phase reactions of certain nucleophiles with alkyl trifluoroacetates. A new probe to distinguish between SN2 and E2 mechanisms for alkyl derivatives

Intramolecular rotation in some alkyl trifluoroacetates at mircowave frequencies

Abstract The permittivity and dielectric loss of methyl and ethyl trifluoroacetates have been measured at three microwave frequencies viz., 24.50, 18.26 and 9.83 GHz and also at 1 MHz and optical frequency at 35°C, in dilute solutions of benzene and decalin. The permittivity and dielectric loss at different frequencies have been plotted against concentration (wt. fraction). The slopes of these straight lines have been used for the complex plane plots (a″ vs a′), which in the case of benzene are Debye semi-circles for the main dispersion region while in decalin are Cole-Cole arcs which show symmetrical distribution of relaxation times. The dispersion curve for these compounds in decalin could not be resolved into two distinct Debye curves because of overlapping of the two dispersion regions. The data have been analysed in terms of two relaxation processes corresponding to overall and group rotations.

Studies in solvolysis. Part I. The neutral hydrolysis of some alkyl trifluoroacetates in water and deuterium oxide

The temperature dependence of the rates of neutral hydrolysis of a series of alkyl trifluoroacetates (CF3COOR; R = methyl, ethyl, s-propyl, t-butyl) has been determined in both light and heavy water. From these studies the thermodynamic parameters (ΔH≠, ΔS≠) which characterize the activation process have been calculated. Sufficient rate data have been obtained in the case of the ethyl ester to calculate the heat capacity of activation (ΔCP≠) for the hydrolysis of this compound in light water. Both the entropies and enthalpies of activation as well as the solvent isotope effects are consistent with the proposal that the primary and secondary esters react by an acyl–oxygen BAc2 mechanism, in contrast to the tertiary ester, which appears to react either by a carbonium ion (SN1) process or by a route which combines both the BAc2 and SN1 paths.