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Several DBU-based protic ionic liquids were facilely synthesized, they were successfully used as solvents and catalysts for alcoholysis of poly(lactic acid) (PLA) to yield lactate esters. The structure of ionic liquids and reaction parameters were optimized. Using [HDBU][AA] as the catalytic medium, which was composed by a 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) cation and an acetate anion, the PLA could be completely depolymerized with a 91% methyl lactate yield under the conditions of 100 °C, 5 mol% catalyst loading for 5 h. The effect of alcohol structures on the catalytic behaviors was studied, and good to excellent product yields were obtained. Moreover, the developed [HDBU][AA] showed excellent recyclability and structure stability. A possible reaction mechanism concerning the synergistic effect of the anion-cation ions was proposed. The DBU-based protic ionic liquids presented herein are low-cost and one-step synthesized, exhibiting great potential as green and efficient platform for direct and selective alcoholysis of PLA. • The facilely obtained DBU-based protic ILs show the higher activity for alcoholysis of poly(lactic acid) compared with the reported catalysts. • The protocol shows great advance for alcoholysis of poly(lactic acid) without additional solvent and metal ions. • The eco-friendly catalysts exhibit excellent stability and can keep durable high-activity after six cycles. • The possible activation and catalytic mechanism concerning the synergistic effect of the anion-cation ions is provided. [ABSTRACT FROM AUTHOR]

The direct conversion of cellulose with metal-triflate catalysts in methanol is investigated. Sn II -triflate remarkably catalyzes the formation of a mixture of useful α-hydroxy esters such as methyl lactate, methyl vinyl glycolate and methyl-4-methoxy-2-hydroxybutanoate, on top of methyl levulinate. Compared to other metal triflates or Sn salts, the catalytic features of Sn II -triflate are distinct and linked to the interplay between its Brønsted and Lewis acidic component. A total ester yield (carbon-based, mol%) in the 60%-range could be obtained from cellulose after 2 h at 200 °C for cellulose loadings up to 20 g L −1 with 4.8 mM of catalyst. The cascade reaction network, confirmed by feeding intermediates, highlights the importance of a fast retro-aldol of the hexose intermediates – opposed to their dehydration – when α-hydroxy esters are targeted. By manipulating the triflate-to-Sn ratio, nearly 40% of α-hydroxy esters can be produced in a one-pot approach. Such mixtures could help fuel the demand for functional biodegradable polyesters. [ABSTRACT FROM AUTHOR]

Highlights: [•] Lactate esters are only resolved when used as acyl acceptors. [•] Only the d enantiomer is acylated whatever the donor/acceptor used. [•] The best acylating agent is butyric anhydride. [•] Lipase B from Candida antarctica is the most efficient enantioselective lipase. [•] The resolution is complete within a few hours in heptane or a solvent free system. [Copyright &y& Elsevier]

Lactate esters are widely used as food additives, perfume materials, medicine additives, and personal care products. The objective of this work was to investigate the effect of a series of lactate esters as penetration enhancers on the in vitro skin permeation of four drugs with different physicochemical properties, including ibuprofen, salicylic acid, dexamethasone and 5-fluorouracil. The saturated donor solutions of the evaluated drugs in propylene glycol were used in order to keep a constant driving force with maximum thermodynamic activity. The permeability coefficient ( Kp), skin concentration of drugs (SC), and lag time ( T), as well as the enhancement ratios for Kp and SC were recorded. All results indicated that lactate esters can exert a significant influence on the transdermal delivery of the model drugs and there is a structure-activity relationship between the tested lactate esters and their enhancement effects. The results also suggested that the lactate esters with the chain length of fatty alcohol moieties of 10–12 are more effective enhancers. Furthermore, the enhancement effect of lactate esters increases with a decrease of the drug lipophilicity, which suggests that they may be more efficient at enhancing the penetration of hydrophilic drugs than lipophilic drugs. The influence of the concentration of lactate esters was evaluated and the optimal concentration is in the range of 5∼10 wt.%. In sum, lactate esters as a penetration enhancer for some drugs are of interest for transdermal administration when the safety of penetration enhancers is a prime consideration. [ABSTRACT FROM AUTHOR]

Alkyl lactates are produced from lactic acid via esterification, and are used in the production of plastics, paints, solvents and detergents. In the pursuit of an inexpensive, industry-suitable catalyst for this reaction, the application of protic ionic liquids based on nitrogen base and sulphuric acid is proposed. The ionic liquid was synthesised via a simple reaction of triethylamine and a threefold molar excess of sulphuric acid. Water was added to remove the heat of the reaction. Next, the reaction conditions for the model esterification of 2-ethylhexanol with lactic acid without additional solvent were optimised. Exceptionally mild conditions, i.e., a twofold molar excess of alcohol to lactic acid with the addition of an ionic liquid in a catalytic amount (15 mol%) at 60 °C, resulted in high yields of ethyl and 2-ethylhexyl lactates (96–97%). The driving force of this reaction is the production of a biphasic system with immiscible ester during the reaction. This phenomenon makes it possible to overcome the reaction equilibrium. Using an inexpensive ionic liquid, which could be recycled up to five times without diminution in conversion or selectivity, leads to both a greener and a more economically-viable process. [ABSTRACT FROM AUTHOR]