Efficient access to aliphatic esters by photocatalyzed alkoxycarbonylation of alkenes with alkyloxalyl chlorides

Aliphatic esters are essential constituents of biologically active compounds and versatile chemical intermediates for the synthesis of drugs. However, their preparation from readily available olefins remains challenging. Here, we report a strategy to access aliphatic esters from olefins through a photocatalyzed alkoxycarbonylation reaction. Alkyloxalyl chlorides, generated in situ from the corresponding alcohols and oxalyl chloride, are engaged as alkoxycarbonyl radical fragments under photoredox catalysis. This transformation tolerates a broad scope of electron-rich and electron-deficient olefins and provides the corresponding β-chloro esters in good yields. Additionally, a formal β-selective alkene alkoxycarbonylation is developed. Moreover, a variety of oxindole-3-acetates and furoindolines are prepared in good to excellent yields. A more concise formal synthesis of (±)-physovenine is accomplished as well. With these strategies, a wide range of natural-product-derived olefins and alkyloxalyl chlorides are also successfully employed.

Use of Kluyveromyces marxianus to Increase Free Monoterpenes and Aliphatic Esters in White Wines

An increasing interest in novel wine productions is focused on non-Saccharomyces yeasts due to their potential in improving sensory profiles. Although Kluyveromyces marxianus has been originally isolated from grapes and its enzymatic activities are used in oenology, rarely it has been used as co-starter. The K. marxianus Km L2009 strain has been characterized here and selected as a co-starter both at laboratory- and winery-scale fermentation. The Km L2009 strain showed growth of up to 40 (mg/L) of sulfites and 6% (v/v) of ethanol. Gas chromatographic analysis demonstrates that wines produced by mixed fermentation contain remarkably higher quantities of free monoterpenes and aliphatic esters than wines produced only by commercial strains of Saccharomyces cerevisiae. Differences in the volatile organic compound composition produced sensorially distinct wines. In light of these results, it is possible to state that even within the K. marxianus species it is possible to select strains capable of improving the aromatic quality of wines.

Efficient Access to Aliphatic Esters by Photocatalyzed Alkoxycarbonylation of Alkenes

Aliphatic esters are essential constituents of biologically active compounds and versatile chemical intermediates for the synthesis of drugs. However, their preparation from readily available olefins remains challenging. In this report, a new strategy to access aliphatic esters from olefins through a unique photocatalyzed alkoxycarbonylation reaction is described. Alkyloxalyl chlorides, generated in situ from the corresponding alcohols and oxalyl chloride, are engaged for the first time as alkoxycarbonyl radical fragments under photoredox catalysis. This transformation tolerates a broad scope of electron-rich and electron-deficient olefins and provides the corresponding β-chloro esters in good yields. Additionally, a formal β-selective alkene alkoxycarbonylation is developed. And, a variety of oxindole-3-acetates and furoindolines are prepared in good to excellent yields. A more concise formal synthesis of (±)-physovenine is accomplished as well. With these strategies, a wide range of natural-product-derived olefins and alkyloxalyl chlorides are also successfully employed.

The controversies of parabens – an overview nowadays

Effects of paraben toxicity, i.e., endocrine-disruption properties, are in the focus of researchers for decades, but still – they are a hot subject of debate. Parabens are aliphatic esters of p-hydroxybenzoic acid, which are widely used as antimicrobial agents for the preservation of cosmetics, pharmaceuticals and foods. Mostly used parabens are methyl-, ethyl-, propyl- and butylparaben. Although the toxicity of parabens is reported in animals and in in vitro studies, it cannot be taken for granted when discussing hazards for human health due to an unrealistic exposure -safety profile. Many studies have demonstrated that parabens are non-teratogenic, non-mutagenic, non-carcinogenic and the real evidence for their toxicity in humans has not been established. For now, methyl-, ethyl- and propylparaben are considered safe for use in cosmetics and pharmaceuticals within the recommended range of doses. Regarding alternatives for parabens, a variety of approaches have been proposed, but every substitute would need to be tested rigorously for toxicity and safety.

Ruthenium-catalysed domino hydroformylation–hydrogenation–esterification of olefins

Aliphatic esters are made easily from acetic acid, olefins, and synthesis gas. In the presence of ruthenium–phosphine complexes novel domino-hydroformylation–hydrogenation–esterification proceeds in moderate to good yields.

Esterification of propanoic acid with 1,2-propanediol: catalysis by cesium exchanged heteropoly acid on K-10 clay and kinetic modelling

Aromatic as well as aliphatic esters are important classes of chemicals having a variety of applications.

On the electronic structure of methyl butyrate and methyl valerate

We present novel results of the analysis of the electronic structure of two aliphatic esters: methyl butyrate and methyl valerate. High-resolution photoabsorption spectra were collected and analyzed over the energy range 4.0–10.8 eV and showed for both the molecules not only a clear band of the HOMO to LUMO transition, but also vibronic structure associated with the first Rydberg-valence transition. Photoelectron spectra recorded from 9 to over 28 eV revealed many ionization states with the first adiabatic ionization energies found to be 9.977 eV and 9.959 eV for methyl butyrate and methyl valerate, respectively. Ab initio calculations have been performed in order to help assign the photoabsorption and photoelectron features. Photolysis life times in the atmosphere were calculated revealing that photolysis is not competitive over hydroxyl radical scavenging in the process of removal of these esters from the atmosphere. Graphical abstract

Ultrasound-Assisted Method for the Synthesis of Tertiary Fatty Aliphatic Esters with Potential Antimicrobial Activity

This study aims to demonstrate a simple and rapid “green” method for the ultrasound-assisted synthesis of t-aliphatic esters by reacting t -butanol with saturated (capric, lauric, palmitic) and unsaturated (oleic and undecylenic) acids. The spectral characterization of esters was performed by IR and NMR spectroscopies. The impact of ultrasonic irradiation on the reaction in comparison with the conventional method was analyzed based on the reaction time and the yield of the resulting esters. After spectroscopic studies, the synthesis of the corresponding esters after the ultrasound-assisted irradiation was proven. The yields of the t-butyl fatty acid esters increased between 2 and 10% in comparison with the conventional method for their synthesis. It was also established that the application of ultrasonic irradiation intensifies the esterification process significantly compared to the conventional method. The advantages of the ultrasound-assisted esterification include shortening the reaction time; the process is carried out at room temperature instead of at the conventional reaction temperature 67-70oC. The application of ultrasonic-assisted irradiation for esterification is a suitable and promising method to reduce energy consumption, shortening the reaction time, and increasing the yield of t -butyl fatty acid esters.