Isopropyl Esters Research Articles

Chemoselective Reduction of Esters to Aldehydes by Potassium Diisobutyl-t-butoxyaluminum Hydride (PDBBA)

The reduction of ester to aldehyde is one of the most useful synthetic transformations in organic synthesis, and a large number of reducing agents for this purpose have been reported. Among them, diisobutylaluminum hydride (DIBALH), which is commercially available, is used as one of the most popular reducing agents, although this reagent provides moderate yields (48-88%) and requires a very low temperature (−78 C). Very recently, we reported that lithium diisobutyl-t-butoxyaluminum hydride (LDBBA) and sodium diisobutyl-t-butoxyaluminum hydride (SDBBA), the alkoxy derivatives of DIBALH, were new partial reducing agents which could reduce various esters to aldehydes. Among them, LDBBA was especially effective for partial reduction of isopropyl esters to aldehydes in most cases with >90% yield at 0 C, and SDBBA was also effective for partial reduction of methyl and ethyl esters in very good yield (73-93%) at 0 C. As a part of our research program directed toward the discovery of new reducing agents through simple modification of commercial DIBALH, we recently found that potassium diisobutyl-t-butoxyaluminum hydride (PDBBA) was easily prepared by reacting an equimolar amount of potassium t-butoxide with DIBALH in THF at 0 C or room temperature (Scheme 1). We applied this reagent for the partial reduction of esters and nitriles to aldehydes. We first examined the partial reduction of representative esters and nitriles such as ethyl benzoate (entry 1 in Table 2), ethyl caproate (entry 15 in Table 2), benzonitrile (entry 19 in Table 2) and capronitrile (entry 20 in Table 2) with PDBBA in THF at 0 C. The reduction of these esters provides corresponding aldehydes in very good yield (88-89%) in 2448 h. In contrast, nitriles were not reduced at all. It was found that PDBBA essentially did not attack nitriles at 0 C. Therefore, partial reduction of esters to the correspondig aldehydes chemoselectively in the presence of nitriles was attempted. Indeed, as shown in Table 1, we achieved quantitative conversion of ethyl benzoate into benzaldehyde in mixtures with benzonitrile, with essentially no reduction of the benzonitrile. Accordingly, we applied PDBBA for the synthesis of aldehydes from various esters. The results for representative esters are summarized in Table 2. As shown in Table 2, ethyl benzoate was efficiently reduced to benzaldehyde in 89% yield (entry 1 in Table 2). Under identical conditions, reduction with DIBALH alone provided only benzyl alcohol (entry 2 in Table 2). Isopropyl benzoate need larger amount of hydride (1.5 eq) than sterically unhindered esters such as ethyl benzoate, presumably due to the bulky isopropyl group (entry 3 in Table 2). Also, esters of electron-withdrawing substituents such as ethyl 4fluorobenzoate, methyl 3-chlorobenzoate, ethyl 4-chlorobenzoate, ethyl 2-bromobenzoate, ethyl 4-bromobenzoate and ethyl 4-nitrobenzoate, and electron-donating substituents such as ethyl 2-toluate, ethyl 4-toluate and ethyl 4-methoxybenzoate were readily reduced to the corresponding aldehydes in 71-91% yield (entries 4-12 in Table 2). Among these, the reduction of ethyl 4-methoxybenzoate required a longer reaction time (48 h) than common esters. This may be attributed to the strong electron donating effect of the methoxy group. Similarly, reduction of other aromatic esters such as ethyl 2-naphthalate, a poly-aromatic ester and ethyl 2-furoate, a heterocyclic ester gave the corresponding aldehydes in 88% and 84% yield, respectively (entries 13 and 14 in Table 2). Furthermore, aliphatic esters such as ethyl caproate, isopropyl caproate, ethyl undecanoate and ethyl cyclohexanecarboxylate were efficiently reduced to the corresponding aldehydes in 78-90% yield (entries 15-18 in Table 2). In summary, we easily prepared PDBBA by reacting commercially available DIBALH with potassium t-butoxide.

Lithium Diisobutyl‐t‐butoxyaluminum Hydride, a New and Efficient Reducing Agent for the Conversion of Esters to Aldehydes.

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Lithium diisobutyl- t-butoxyaluminum hydride, a new and efficient reducing agent for the conversion of esters to aldehydes

Lithium diisobutyl- t-butoxyaluminum hydride (LDBBA), easily prepared by reaction of lithium t-butoxide with DIBALH, readily reacts with common aromatic and aliphatic esters to give the corresponding aldehydes in 74–88% yield at 0 °C. Especially, this reagent proved to be the most effective partial reducing agent for conversion of isopropyl esters to aldehydes, in most cases, with >90% yield under the same reaction temperature.

Synthesis of a green biosolvent: Isopropyl esters: A statistical approach

The synthesis of a green clean biosolvent, isopropyl esters, using high-oleic sunflower oil (HOSO) as raw material over an enzymatic catalyst, has been developed and optimized following a factorial design and response surface methodology. A full three-factorial design has proved effective in the study of the influence of the variables (temperature, enzyme concentration, and alcohol/oil molar ratio) on the process. The process was studied in the range of 68–82 °C, 1.8–8.4% wt. catalyst concentration, and initial alcohol/oil molar ratio 1:1–11:1. The molar ratio of alcohol/oil was been found to be the most significant factor on the transesterification process and its influence is negative. The response surface model obtained, representing the yield of ester, was found to describe adequately the experimental results. The best conditions for the process are a catalyst concentration of 7%, an operation temperature of 71 °C and with low alcohol/oil molar ratio (3:1); with these conditions the maximum conversion obtained was 84%. The preparation of the product is a green engineering process, clean, solvent-free, with a very selective catalyst that minimizes water and energy consumption and the downstream processing of the integrated process.

Synthesis of alkyl 6‐methyl‐4‐(2‐trifluoromethylphenyl)‐1,2,3,4‐tetrahydro‐2H‐pyrimidine‐2‐one‐5‐carboxylates possessing a N‐3 nitro substituent to determine calcium channel modulation structure‐activity relationships

Abstractmagnified imageThe Bigenelli acid catalyzed condensation of 2‐trifluoromethylbenzaldehyde (1), urea (2) and an alkyl acetoacetate (3) afforded the respective alkyl (Me, Et, i‐Pr, i‐Bu) 6‐methyl‐4‐(2‐trifluoromethylphenyl)‐1,2,3,4‐tetrahydro‐2H‐pyrimidine‐2‐one‐5‐carboxylate (4‐7). Subsequent N3‐nitration of the alkyl esters (4‐7) using Cu(NO3)2 3H2O and Ac2O furnished the target alkyl 6‐methyl‐3‐nitro‐4‐(2‐trifluoromethylphenyl)‐1,2,3,4‐tetrahydro‐2H‐pyrimidine‐2‐one‐5‐carboxylates (8‐11). The N3‐nitro compounds (8‐11) were less potent calcium channel antagonists (IC50 values in the 1.9 × 10−7 to 3.9 × 10−6 M range) on guinea pig ileal longitudinal smooth muscle than the reference drug nifedipine (Adalat®, IC50 = 1.4 × 10−8 M). In vitro calcium channel modulation studies on guinea pig left atrium (GPLA) showed that the methyl and ethyl esters (8‐9) induced a weak‐to‐modest positive inotropic (agonist) effect, and that the inactive isopropyl (10) and isobutyl (11) esters did not alter the cardiac contractile force of GPLA.

Scandium Triflate Catalyzed Transesterification of Carboxylic Esters

The direct transesterification of carboxylic esters is efficiently catalyzed with Sc(OTf)3 (10 mol%) in boiling alcoholic solvent. Methyl, ethyl, isopropyl, and allyl esters were prepared from a broad range of different substrates in high yields. The application of microwave irradiation led to significantly reduced reaction times.

Synthesis and properties of N-nicotinoyl-2-(5-fluorouracil-1-yl)- d, l-glycine ester as a prodrug of 5-fluorouracil for rectal administration

N-Nicotinoyl-2-(5-fluorouracil-1-yl)- d, l-glycine (NFG) methyl-(NFGM), ethyl-(NFGE) and isopropyl esters (NFGIp) were synthesized and their potential as a prodrug of 5-fluorouracil (5-FU) for rectal administration was investigated. Chemical conversion proceeded either by elimination of (5-FU) or by hydrolysis of ester group. 5-FU was released from NFGIp, NFGE and NFGM 90.5%, 71.3% and 48.5% of the dose, respectively, in 80% human plasma and 79.8%, 56.3% and 31.6%, respectively, in pH 7.4 buffer solution after 48 h of incubation at 37 °C. Release of 5-FU occurred mainly from NFG esters but very slightly from NFG, which suggested that release of 5-FU was greatly dependent on the stability of the ester group against hydrolysis. Solubility ( M) in pH 7.4 buffer solution was 0.13, 0.09 and 0.04 and apparent partition coefficient in 1-octanol/pH 7.4 buffer solution was 0.76, 1.61 and 4.2, respectively, for NFGM, NFGE and NFGIp, which were in the ranges suitable for rectal absorption. Plasma concentration (μg/mL) of NFGM, NFGE and NFGIp at 50 min after rectal administration to rats was 1.9, 4.6 and 6.7, respectively, and that for 5-FU was below the limit of detection. Their potential as prodrugs of 5-FU for rectal administration is suggested.

Isolation and melting properties of branched‐chain esters from lanolin

AbstractSaturated branched FA and their derivatives are both biodegradable and stable to oxidation. Their m.p. are expected to be enough lower than their straight‐chain counterparts to make them ideal as biolubricants. But physical property data for branched fatty esters are limited. In this study, a complex mixture of branched methyl esters was obtained from lanolin through saponification, extraction of unsaponifiables, and methylation. Hydroxy compounds were removed by chromatography on alumina. Vacuum spinning‐band distillation separated the mixture roughly by chain length. Countercurrent urea complex formation and low‐temperature crystallization separated even‐chain iso‐and odd‐chain anteiso‐methyl esters of chain lengths 14 through 18 at >95% purity. Transesterification was used to convert methyl esters to isopropyl esters. The m.p. and heat of fusion of each ester were determined by DSC. NMR was used to verify the structure of branched esters.

(S)-4,5-Dihydro-2-(2-hydroxy-4-hydroxyphenyl)-4-methyl-4-thiazolecarboxylic Acid Polyethers: A Solution to Nephrotoxicity

Previous studies revealed that within a family of ligands the more lipophilic chelators have better iron-clearing efficiency. The larger the log P(app) value of the compound, the better the iron-clearing efficiency. What is also clear from the data is that although the relative effects of log P(app) changes are essentially the same through different families, there are differences in absolute value between families. However, there also exists a second, albeit somewhat more disturbing, relationship. In all sets of ligands, the most lipophilic chelator is always the most toxic. The current study focuses on designing ligands that balance the lipophilicity/toxicity problem while iron-clearing efficiency is maintained. Earlier studies with (S)-4,5-dihydro-2-(2-hydroxy-4-methoxyphenyl)-4-methyl-4-thiazolecarboxylic acid [(S)-4'-(CH(3)O)-DADFT, 6] indicated that this methyl ether was a ligand with excellent iron-clearing efficiency in both rodents and primates; however, it was too toxic. On the basis of this finding, a less lipophilic, more water-soluble ligand than 6 was assembled, (S)-4,5-dihydro-2-[2-hydroxy-4-(3,6,9-trioxadecyloxy)phenyl]-4-methyl-4-thiazolecarboxylic acid [(S)-4'-(HO)-DADFT-PE, 11], a polyether analogue, along with its ethyl and isopropyl esters. The parent polyether and its isopropyl and ethyl esters were all shown to be highly efficient iron chelators in both rodents and primates. A comparison of 11 in rodents with the desferrithiocin analogue (S)-4,5-dihydro-2-(2,4-dihydroxyphenyl)-4-methyl-4-thiazolecarboxylic acid [(S)-4'-(HO)-DADFT, 1] revealed the polyether to be more tolerable, achieving higher concentrations in the liver and significantly lower concentrations in the kidney. The lower renal drug levels are in keeping with the profound difference in the architectural changes seen in the kidney of rodents given 1 versus those treated with 11.

Novel chiral selectors anchored on polydimethylsiloxane as stationary phases for separation of derivatized amino acid enantiomers by capillary gas chromatography

Six chiral selectors of S-(-)-t-Leu-cyclopropylamide, S-(-)-t-Leu-cyclopentylamide, S-(-)-t-Leu-cyclohexylamide, S-(-)-t-Leu-cycloheptylamide, S-(-)-t-Leu-cyclooctylamide, S-(-)-t-Leu-cyclododecylamide have been prepared and anchored individually through amide bonding to a polydimethylsiloxane functionalized with 2,2,2-trifluoroethyl ester groups by way of nucleophilic displacement reaction. The resulting chiral polysiloxanes have been provided as stationary phases for the separation of amino acid enantiomers by capillary GC. Amino acids were derivatized into N(O)-trifluoroacetyl isopropyl esters. Especially, polydimethylsiloxane anchored with S-(-)-t-Leu-cyclooctylamide was found to be efficient for the separation of aspartic acid (Asp) enantiomers. The method was applied to the estimation of ages from the extent of Asp racemization in human dentines.

Low level determination of p-toluenesulfonate and benzenesulfonate esters in drug substance by high performance liquid chromatography/mass spectrometry

GC/FID and HPLC/MS single ion monitoring methods have been evaluated for the determination of trace levels of methyl, ethyl and isopropyl esters of p-toluenesulfonic acid and methyl, ethyl, isopropyl and n-butyl esters of benzenesulfonic acid in drug substances. These sulfonate esters have been highlighted as potential genotoxins. HPLC/MS was found to be more promising and limits of quantification were between 2.5 and 5 ng/mL, which enabled detection limits in drug substance at 0.01–0.1 ppm for a 50 mg/mL solution. For one drug substance excellent recoveries of 94–95% were obtained at the 1.0 ppm level, however, with a second drug substance, a besylate salt, recoveries ranged from 86% to 100% and were dependant on the sample preparation. Limited stability of the sulfonate esters in various potential sample solutions indicated that samples may need to be prepared immediately before injection.

Cuticular waxes from potato ( Solanum tuberosum) leaves

The qualitative and quantitative compositions of leaf cuticular waxes from potato ( Solanum tuberosum) varieties were studied. The principal components of the waxes were very long chain n-alkanes, 2-methylalkanes and 3-methylalkanes (3.1–4.6 μg cm −2), primary alcohols (0.3–0.7 μg cm −2), fatty acids (0.3–0.6 μg cm −2), and wax esters (0.1–0.4 μg cm −2). Methyl ketones, sterols, β-amyrin, benzoic acid esters and fatty acid methyl, ethyl, isopropyl and phenylethyl esters were found for the first time in potato waxes. The qualitative composition of the waxes was quite similar but there were quantitative differences between the varieties studied. A new group of cuticular wax constituents consisting of free 2-alkanols with odd and even numbers of carbon atoms ranging from C 25 to C 30 was identified.

Simple reduction of ethyl, isopropyl and benzyl aromatic esters to alcohols using sodium borohydride-methanol system

Several aromatic ethyl, isopropyl and benzyl esters were reduced to their corresponding alcohols in sodium borohydride-methanol system. The reductions were completed within 15-60 minutes in refluxing THF. The alcohol products were isolated after aqueous workup in good to excellent yields (63-100%). The general procedure presented is simple, safe, inexpensive and with good perspective in industrial scale.

The production of fatty acid isopropyl esters and their use as a diesel engine fuel

AbstractBiodiesel is an alternative fuel for diesel engines that consists of the monoalkyl esters of vegetable oils or animal fats. Currently, most biodiesel consists of methyl esters, which have poor cold‐flow properties. Methyl esters of soybean oil will crystallize and plug fuel filters and lines at about 0°C. However, isopropyl esters have better cold‐flow properties than methyl esters. This paper describes the production of isopropyl esters and their evaluation in a diesel engine. The effects of the alcohol amount, the catalyst amount, and two different catalysts on producing quality biodiesel were studied. Both sodium isopropoxide and potassium isopropoxide were found to be suitable for use in the transesterification process. A 20∶1 alcohol/TG molar ratio and a catalyst amount equal to 1% by weight (based on the TG amount) of sodium metal was the most cost‐effective way to produce biodiesel fuel. The emissions from a diesel engine running on isopropyl esters made from soybean oil and yellow grease were investigated by comparing them with No. 2 diesel fuel and methyl esters. For nitrogen oxide emission, the difference between the biodiesel produced from soybean oil and yellow grease was greater than the difference between the methyl and isopropyl esters of both feedstocks. The other emissions from using isopropyl esters were about 50% lower in hydrocarbons, 10–20% lower in carbon monoxide, and 40% lower in smoke number when compared with No. 2 diesel fuel.

Volatile Compounds in Shoulder Gland Secretions of Male Flying Foxes, Genus Pteropus (Pteropodidae, Chiroptera)

The shoulder gland secretions of captive males of the Indian flying fox (Pteropus giganteus), the little golden-mantled flying fox (P. pumilus), the island flying fox (P. hypomelanus), and the large flying fox (P. vampyrus) were examined by gas chromatography-mass spectrometry. Sixty-five compounds, including hydrocarbons, carboxylic acids, alcohols, aldehydes, ketones, esters, and amides, were identified among the four species. Many of these compounds, such as squalene, cholesterol, and C5-C16 straight- and branched-chain carboxylic acids, are typical of tetrapod epidermal products. Aldehydes, which were detected in all four Pteropus species, and some straight- and branched-chain ketones, which were detected in P. hypomelanus and P. pumilus, are known from other mammalian skin glands. Acetophenone, 4-acetoxyacetophenone, and 4-hydroxyacetophenone were observed in P. pumilus; the last compound comprised 37.1% of the total ion current. 2,3-Butanediol, a prominent component (5.2-19.3%) in the secretions of P. giganteus, P. hypomelanus, and P. pumilus, and C10 and C12 isopropyl esters and C10-C14 1-methylbutyl esters, observed in P. hypomelanus and P. vampyrus, have not previously been reported from vertebrates. alpha-Methyl-4-methoxybenzyl alcohol and dihydro-5-phenyl-2(3H)-furanone, from P. giganteus and P. pumilus, are new natural products. 1-Chloro-3-methyl-2-butene, another new natural product, and five C5 compounds exhibiting a similar isoprenoid structure were observed in P. giganteus. Striking contrasts were observed in the chemical profiles of the species we examined, with even general chemical classes differentially represented among them.

Comparative Liquid Chromatographic Enantiomer Resolution on Two Chiral Stationary Phases Derived from Amylose Tris(3,5-dimethylphenylcarbamate)

Polysaccharide-derived chiral stationary phases (CSPs) are known to show high chiral recognition ability in HPLC and have been extensively used to separate a broad range of racemic compounds. These type CSPs are usually prepared coating or adsorbing the polysaccharide derivatives on silica gel. Therefore, the solvents such as chloroform, methylene chloride, and tetrahydrofuran which dissolve or swell the chiral selectors of the polysaccharide derivatives cannot be used as mobile phases. For example, in case of Chiralpak AD prepared by coating amylose tris(3,5dimethylphenylcarbamate) derivative, one of the widely used polysaccharide type CSPs, suitable mobile phases like hexane, 2-propanol and ethanol should be used for the column safety. It may be damaged in case of even the use of only a little amount of inappropriate solvents used as mobile phases and/or sample solvents. These limitations represent a disadvantage for new applications using these CSPs and, especially, preparative separation due to solubilization of analytes. To overcome these problems, therefore, the development of polysaccharide-derived covalently bonded CSPs has been of great interest and various results of different attempts have been reported. Recently, Chiralpak IA prepared by chemically bonding amylose tris(3,5-dimethylphenylcarbamate) derivative on silica gel, which is used as the same chiral selector of coated type Chiralpak AD has been introduced. In this study, we present the comparative liquid chromatographic enantiomer resolution of N-fluorenylmethoxycarbonyl (FMOC) protected αamino acids ethyl ester derivatives on two polysaccharidederived CSPs, covalently bonded type Chiralpak IA and coated type Chiralpak AD. This is the first report concerning the comparison of the chiral separations on Chiralpak IA and Chiralpak AD using normal mobile phases. For enantiomer separation of N-FMOC α-amino acids ester derivatives, very a few results on CSPs have been reported. Rizzi has separated three FMOC α-amino acids methyl esters enantiomers on cellulose triacetate type column. Miyazawa et al. have reported on the resolution of only one analyte of FMOC 2-aminobutanoic acid methyl ester enantiomers among many different N-protected amino acid derivatives. Kusters et al. have reported on the resolution of fifteen N-FMOC α-amino acids methyl and isopropyl esters enantiomers on a polysaccharide-derived CSP. To our knowledge, our results are the first reported for the enantiomer resolution of N-FMOC α-amino acids ethyl ester derivatives. Table 1 shows the effect of mobile phase on the enantiomer separation of some N-FMOC α-amino acids ethyl esters on Chiralpak IA. The enantioselectivities and retention times are greatly influenced by the nature of mobile phase. As shown in Table 1, in general, 5% 2propanol in hexane as a mobile phase afforded the greatest enantioselectivity with the highest resolution factor, whereas 20% chloroform in hexane afforded the lowest enantioselectivity. It is notable that the elution orders of three analytes using 10% tetrahydrofuran or 10% ethyl acetate or 20% chloroform in hexane are different from those using 5% 2-propanol in hexane. Table 2 shows the comparative data of enantiomer separation of N-FMOC α-amino acids ethyl esters on Chiralpak IA and Chiralpak AD using 2-propanol in hexane as a mobile phase. In general, Chiralpak IA showed slightly lower enantioseparation than Chiralpak AD for enantioresolution of N-FMOC α-amino acids ethyl esters. Several results have reported that a certain decrease in the enantio-

Ytterbium Triflate Promoted Tandem One-Pot Oxidation—Cannizzaro Reaction of Aryl Methyl Ketones.

For Abstract see ChemInform Abstract in Full Text.

Enantiomer separation by reversed-phase liquid chromatography with novel hydrophobic phases composed of chiral cationic surfactants

This paper describes enantiomer separation using four kinds of chiral stationary phases (CSPs) where quaternary ammonium surfactants containing l-valine diamide moieties into long alkyl chains were bound to silicagel supports by reversed phase liquid chromatography. Our aim was to examine hydrogen bonding association of the chiral moiety in hydrophobic phase brought about by aggregation of the micelle-forming surfactants on the surface. The following CSPs were thus derived from the vinyl-terminated chiral surfactants via hydrosilylation: CSP 1 from N-[3-(10-undecenoyl- l-valylamino)propyl]- N, N, N-trimethylammonium bromide, CSP 2 from N-[6-(10-undecenoyl- l-valylamino)hexyl]- N, N, N-trimethyl-ammonium bromide, CSP 3 from N-[3-(10-undecenoyl- l-valylamino)propyl]- N-octadecanyl- N, N-dimethyl-ammonium bromide and CSP 4 from N-[6-(10-undecenoyl- l-valylamino)hexyl]- N-octadecanyl- N, N-dimethylammonium bromide. The degree of hydrophobicity in the interfacial phase was observed by measuring pyrene fluorescence in aqueous media including an organic modifier. Retention of racemic N-acylleucine isopropyl esters was highest in CSP 4, followed by 3, 2, and 1. Largest α values toward enantiomer separation were observed for CSP 4 where the chiral moieties were kept through a hexamethylene unit apart from the polar head groups and to which another long alkyl chain was attached, as compared with those for CSP 4. In CSP 4, the chiral moiety to interact with enantiomeric solutes should be buried into the interfacial phase deeply in more extent than CSP 3. In a similar manner, CSP 2 has more effective for enantiomer separation than CSP 1. The interfacial phase of these CSPs was easily exposed to the bulk phase because of the affinity between the bulk phase and the polar head groups as well as their electrostatic repulsion. However, degree of the enantiomer separation can be controlled by the depth of the chiral moiety in the hydrophobic interfacial phase.

Key fuel properties of palm oil alkyl esters

Methyl esters of vegetable oils have been successfully evaluated as diesel substitute. In the present study, other alkyl esters, namely ethyl and isopropyl esters of crude palm oil and crude palm stearin were synthesized via chemical transesterification reactions and subsequently evaluated for their fuel properties. Generally, these alkyl esters exhibit higher viscosity (4.4×10 −6m 2/s–5.2×10 −6 m 2/s) compared to that of petroleum diesel (4.0×10 −6 m 2/s). However, compared to petroleum diesel, these alkyl esters exhibit acceptable gross heat of combustion (39–41 MJ/kg). Originated from renewable origin, the low sulfur content in alkyl esters emits much lower SO 2. These alkyl esters are much safer than petroleum diesel in terms of safety for storage and transportation as they possess high flash points. They may find applications in the fuel industry besides utilization as oleochemicals.

Ytterbium Triflate-Promoted Tandem One-Pot Oxidation−Cannizzaro Reaction of Aryl Methyl Ketones

[reaction: see text] Ytterbium triflate was shown to be an effective catalyst in promoting the synthesis of either isopropyl esters or free alpha-hydroxy-arylacetic acids from substituted aromatic glyoxals and aryl methyl ketones, respectively. The reaction to provide acids starting from differently substituted ketones was carried out by an environmentally friendly method using an aqueous medium as a solvent and giving the adducts in 78-99% yield without any further purification after the usual workup.