Acids In High Yields Research Articles

ChemInform Abstract: Suzuki—Miyaura Reactions of 3,5‐Dichloro‐2,4,6‐trifluoropyridine.

Abstract 3,5-Diaryl-2,4,6-trifluoropyridines and 5-aryl-3-chloro-2,4,6-trifluoropyridines were prepared through Suzuki–Miyaura reactions of 3,5-dichloro-2,4,6-trifluoropyridine with arylboronic acids in high yields.

Cinchona-catalysed, Enantioselective Synthesis of β-Peroxycarboxylic Acids, β-Peroxyesters and β-Peroxyalcohols

A cinchona-catalysed, enantioselective oxa-Michael reaction of α,β-unsaturated aldehydes with either tert-butyl hydroperoxide or cumene hydroperoxide was developed. The reaction was optimised by screening of solvents, modification of the catalyst framework and variation of the acid co-catalysts. A strong relationship was noted between the pKa of the acid co-catalyst and the degree of selectivity. Enantioselective peroxidation of α,β- unsaturated aldehydes with tert-butyl hydroperoxide afforded β-peroxyaldehydes with good enantioselectivities. In situ oxidation of the latter compounds furnished β-peroxycarboxylic acids in high yields. Enantiomeric excesses were determined by derivitisation to their mandelate esters and subsequent separation by chiral high performance liquid chromatography. Peroxidation with cumene hydroperoxide was similarly successful with the products being isolated as stable β-peroxyalcohols. These latter β-peroxyalcohols offer a direct route to 5-membered, chiral cycloperoxides via a silver-mediated cyclisation. This reaction proceeds by trapping of the oxygen lone pair by the incipient carbocation followed by loss of the cumyl or tert-butyl group and formation of the cycloperoxide product. Keywords: Organocatalysis, cinchona, peroxidation, peroxyacids, peroxyesters, peroxyalcohols, cycloperoxides.

ChemInform Abstract: Palladium‐Catalyzed Carboxylation of Activated Vinylcyclopropanes with CO2.

AbstractThe intermediate in this reaction seems to be a nucleophilic η1‐allylethylpalladium species, arising from π‐allylpalladium and ZnEt2 (umpolung).

Cascade Biocatalysis for Sustainable Asymmetric Synthesis: From Biobased l‐Phenylalanine to High‐Value Chiral Chemicals

AbstractSustainable synthesis of useful and valuable chiral fine chemicals from renewable feedstocks is highly desirable but remains challenging. Reported herein is a designed and engineered set of unique non‐natural biocatalytic cascades to achieve the asymmetric synthesis of chiral epoxide, diols, hydroxy acid, and amino acid in high yield and with excellent ee values from the easily available biobased l‐phenylalanine. Each of the cascades was efficiently performed in one pot by using the cells of a single recombinant strain over‐expressing 4–10 different enzymes. The cascade biocatalysis approach is promising for upgrading biobased bulk chemicals to high‐value chiral chemicals. In addition, combining the non‐natural enzyme cascades with the natural metabolic pathway of the host strain enabled the fermentative production of the chiral fine chemicals from glucose.

Cascade Biocatalysis for Sustainable Asymmetric Synthesis: From Biobased l-Phenylalanine to High-Value Chiral Chemicals.

Sustainable synthesis of useful and valuable chiral fine chemicals from renewable feedstocks is highly desirable but remains challenging. Reported herein is a designed and engineered set of unique non-natural biocatalytic cascades to achieve the asymmetric synthesis of chiral epoxide, diols, hydroxy acid, and amino acid in high yield and with excellent ee values from the easily available biobased l-phenylalanine. Each of the cascades was efficiently performed in one pot by using the cells of a single recombinant strain over-expressing 4-10 different enzymes. The cascade biocatalysis approach is promising for upgrading biobased bulk chemicals to high-value chiral chemicals. In addition, combining the non-natural enzyme cascades with the natural metabolic pathway of the host strain enabled the fermentative production of the chiral fine chemicals from glucose.

Fmoc-OASUD: A new reagent for the preparation of Fmoc-amino acids free from impurities resulting from Lossen rearrangement

A new reagent, 9-fluorenylmethoxy-carbonyl-N-hydroxy-3-azaspiro[5,5]undecane-2,4-dione ester (Fmoc-OASUD) for the preparation of Fmoc-amino acids is described. The Fmoc-OASUD reacts with amino acids at room temperature in the presence of a base and gives Fmoc-amino acids in high yields and purity. The Fmoc-amino acids prepared using Fmoc-OASUD are free from impurities due to Lossen rearrangement, which are generally present when Fmoc-OSu is used. This is mainly because of the higher stability of Fmoc-OASUD compared to Fmoc-OSu.

Enantioselective amination of acyclic α-alkylated β-keto esters catalyzed by chiral lithium binaphtholate

The enantioselective amination of α-alkylated β-keto esters with azodicarboxylates using a chiral dilithium binaphtholate as catalyst affords optically active α,α-disubstituted α-amino acid derivatives in high enantioselectivities of up to 95% ee. A stoichiometric amount of lithium hydroxide accelerates the amination. This method provides easy access to various chiral α,α-disubstituted α-amino acids in high yields and with high enantioselectivities from readily available starting materials and chiral sources.

Palladium-Catalyzed Carboxylation of Activated Vinylcyclopropanes with CO2.

By using a palladium catalyst with ZnEt2, activated vinylcyclopropanes were successfully converted into the corresponding β,γ-unsaturated carboxylic acids in high yields under a CO2 atmosphere (1 atm). The intermediate in this reaction is thought to be a nucleophilic η(1)-allylethylpalladium species, which would be produced from π-allylpalladium and ZnEt2 (umpolung reactivity).

Suzuki–Miyaura reactions of 3,5-dichloro-2,4,6-trifluoropyridine

3,5-Diaryl-2,4,6-trifluoropyridines and 5-aryl-3-chloro-2,4,6-trifluoropyridines were prepared through Suzuki–Miyaura reactions of 3,5-dichloro-2,4,6-trifluoropyridine with arylboronic acids in high yields.

Cp2TiCl2-Catalyzed Regioselective Hydrocarboxylation of Alkenes with CO2.

Cp2TiCl2-catalyzed regioselective hydrocarboxylation of alkenes with CO2 to give carboxylic acids in high yields has been developed in the presence of (i)PrMgCl. The reaction proceeds with a wide range of alkenes under mild conditions. Styrene and its derivatives can transform to α-aryl carboxylic acids, and aliphatic alkenes can transform to form alkanoic acids.

A Sustainable Route to a Terephthalic Acid Precursor.

A new synthetic pathway for the production of p-toluic acid has been developed starting from reagents derived from renewable resources. A Diels-Alder reaction between sorbic and acrylic acids is followed by a combined dehydrogenation/ decarboxylation process, providing p-toluic acid in high yields. This route permits to use milder conditions compared to other Diels-Alder approaches reported in the literature, and therefore can contribute to a more sustainable terephthalic acid production.

A facile and rapid preparation of hydroxamic acids by hydroxylaminolysis using DBU as base

While there are many protocols for the preparation of hydroxamic acids from their corresponding carboxylic acid or carboxylic ester precursors, most use strong mineral bases that can lead to carboxylic acid impurities that can be difficult to remove using standard chromatographic techniques. This problem is exacerbated when the carbonyl group is hindered. Herein, we communicate a robust hydroxylaminolysis protocol for the preparation of hydroxamic acids in high yield and purity.

One‐Pot, Clean Synthesis of Vanillic Acid from Ferulic Acid

AbstractFerulic acid dissolved in water is selectively oxidized to vanillic acid in high yield (≈60 %) under remarkably mild and green conditions, namely at room temperature with air as primary oxidant, over a catalytic amount of nanostructured Bi2WO6. The process is general and opens the route to the selective oxidation of natural substances into derivatives of significant applicative relevance.

Approach to the synthesis of 8-nitroquinoline-2-carboxylic acid in high yield

A synthesis of 8-nitroquinoline-2-carboxylic acid was optimized, using the following basic scheme of transformations: 1) nitration of 2-methylquinoline with subsequent separation of a mixture of isomeric 8-nitroand 5-nitro-2-methylquinolines; 2) oxidation of the methyl group in 2-methyl-8-nitroquinoline (including consecutive steps of bromination and hydrolysis in aqueous sulfuric acid). A new method for the separation of isomeric 8-nitroand 5-nitro-2methylquinolines was suggested. The optimal conditions for the final step of hydrolysis were selected, which gave almost quantitative yield of 8-nitroquinoline-2-carboxylic acid.

Selective oxidation of glucose to glucuronic acid by cesium-promoted gold nanoparticle catalyst

Gold catalysts outperform palladium and platinum catalysts for the oxidation of sugars with high activity and selectivity toward aldonic acids. The oxidation into other sugar acids, such as uronic and aldaric acids, has been scarcely investigated. Au nanoparticles supported on CeO2 using a soft chemical reduction method with hydrazine, were active for the selective oxidation of low weight carbohydrates (glucose, fructose, maltose) into glucuronic acid. The oxidation occurred in aqueous solution at low temperature using O2 as oxidant and without adding any base. The activity was improved by modifying the supported Au catalyst with cesium, while selectivity was maintained. Under these conditions, high selectivity to glucuronic acid was achieved; however, in the presence of base many by-products were obtained. The preparation of glucuronic acid in high yield using gold catalysts was never reported, which makes the catalyst developed here very interesting for liquid phase oxidation processes.

High-yield methods for purification of α-linolenic acid from Perilla frutescens var. japonica oil

This study was conducted to investigate the purification methods for high-yield of α-linolenic acid (ALA) from Perilla frutescens var. japonica oil (PO). PO was treated with 2 g of urea, cooled for 24 h, and 81.75 % of ALA was obtained after gas chromatography–flame ionization detector analysis. Urea complexation at low temperature (refrigeration) is a prospective method for the extraction of unsaturated fatty acids in high yields. Our results suggest that urea treatment with cooling at 10 °C could be used for purification of ALA from PO. It will be enhanced for the development of nutritional, medical, and cosmetic value.

Direct production of levulinic acid in high yield from cellulose: joint effect of high ion strength and microwave field

Cellulose without any pretreatment was directly converted into levulinic acid (LA) in a microwave-assisted acidic catalytic system with a high ionic strength. The highest LA yield could reach 67.3 mol% within 60 min even when the cellulose concentration was as high as 10 wt%. It is concluded that high ion strength and microwave irradiation were jointly responsible for the fast cellulose conversion and high LA yield, and a cooperative acceleration mechanism is finally proposed. The high ion concentration provided by alkali metal halides not only accelerated the cellulose hydrolysis but also facilitated glucose conversion into LA by shifting the weak acid ionization equilibria, and microwave irradiation further promoted this salt effect by its characteristic heating way of ion conduction. Such a one-pot catalytic system provides a possibility of practical application for direct highly efficient conversion of cellulose due to its green properties, low cost and efficient characteristics.

Change in reactivity of differently capped AuPd bimetallic nanoparticle catalysts for selective oxidation of aliphatic diols to hydroxycarboxylic acids in basic aqueous solution

N,N-Dimethyldodecylamine N-oxide (DDAO), PVP and PVA capped supported AuPd bimetallic nanoparticles (NPs) were prepared, and their catalytic activities were evaluated for the oxidation of 1,6-hexanediol (HDO) to 6-hydroxycaproic acid (HCA) using H2O2 in basic aqueous solution. Among three catalysts, DDAO capped AuPd bimetallic NPs catalysts exhibited superior selectivity for HCA formation than PVP and PVA capped catalysts. To explain the difference in the catalytic behavior, the catalysts were characterized thoroughly. XRD, TEM and STEM-HAADF-EDS studies were employed to identify the structure and morphology of capped AuPd-NPs, respectively. The chemical and electronic states were elucidated using XPS and XAS methods. The characterization data revealed that the capping agent significantly influences the electron density on metals and extent of alloying between Au and Pd metals. It was revealed that DDAO-capped catalyst induces appropriate negatively charged Au species with a few numbers of Au–Pd interfaces for the highly selective formation of HCA via HDO oxidation in basic aqueous media. Furthermore, other aliphatic diols, 1,7-heptanediol, 1,8-octanediol and 1,2-hexanediol, were also selectively oxidized on AuPd-DDAO catalysts toward the corresponding ω-hydroxycarboxylic acids in high yields.

Glycosylation and functionalization of native amino acids with azido uronic acids

Bifunctional, acetyl-protected, azido glucuronic and galacturonic acid derivatives were coupled via the carboxylic acid moiety to amine- and hydroxyl-containing side chains of the natural amino acids lysine and serine or via the N-terminus of the amino acids leucine, methionine and glutamine. The glycosylated amino acids were then functionalized via the free azido moiety to produce the corresponding anomeric triazole derivatives. This approach enables the dual glycosylation and functionalization of a range of native amino acids in high yields.

Direct Catalytic Asymmetric Mannich-Type Reaction of α-N3 Amide.

An α-N3 7-azaindoline amide serves as a latent enolate to directly engage in an asymmetric Mannich-type reaction with N-thiophosphinoyl imines by the action of a cooperative catalyst. The thus-obtained highly enantioenriched anti-adduct was transformed into β-amino-α-azido acid in high yield by simple acidic treatment.