A Green Approach for Producing Solvent-free Anisyl Acetate by Enzymecatalyzed Direct Esterification in Sponge-like Ionic Liquids Under Conventional and Microwave Heating

Title:A Green Approach for Producing Solvent-free Anisyl Acetate by Enzymecatalyzed Direct Esterification in Sponge-like Ionic Liquids Under Conventional and Microwave Heating

Volume: 1 Issue: 2

Author(s): Pedro Lozano, Juana M. Bernal, Almudena Lajarin, Daniel Romera, Eduardo Garcia-Verdugo, Gregorio Sanchez-Gomez, Mathieu Pucheault, Michel Vaultier, M. Isabel Burguete and Santiago V. Luis

Affiliation:

Keywords: Anisyl acetate, anisyl alcohol, biocatalysis, biocatalytic process, clean process, enzymatic synthesis, esterification, flavours, fragrances, green chemistry, ionic liquids, lipase, neoteric solvents, pure products, solvent-free, sponge-like ionic liquids, sustainable chemistry, switchable ionic liquids.

Abstract: The biocatalytic synthesis of anisyl acetate fragrance was carried out by direct esterification of acetic acid with anisyl alcohol in sponge-like ionic liquids (SLILs), e.g. N,N,N,N-hexadecyltrimethylammonium bis(trifluoromethylsulfonyl) imide ([C₁₆tma][NTf₂], N,N,N,N-octadecyltrimethylammonium bis(trifluoromethylsulfonyl)imide ([C₁₈tma] [NTf₂]), etc. as reaction/separation media under conventional and microwave (MW) heating. These SLILs are temperatureswitchable ionic liquid/solid phases that behave as sponges. As liquid phases, they are excellent monophasic reaction media for the lipase-catalyzed synthesis of anisyl acetate, the product yield being improved up to 100% for 2 hour reaction under the appropriate reaction conditions (i.e. SLIL concentration, alcohol: acid molar ratio, enzyme amount, dehydrating molecular sieves, temperature and MW heating). As a function of the phase behaviour of different SLIL/anisyl acetate mixtures, a new clean separation protocol based on the centrifugation of the solid IL/flavour ester through nylon membranes was proposed, which provided a nearly full separation of the solid SLIL and the easy recovery of the reaction mixture. The enzymatic synthesis of anisyl acetate in [C₁₆tma] [NTf₂] under MW assistance, followed by the separation step of the solid SLIL, provided a nearly solvent-free fragrance product with up to 0.89 g/mL concentration. The catalytic activity of the enzyme / SLIL system remained unchanged for ten consecutive operational cycles. This work reports a straightforward and sustainable approach for producing anisyl acetate as a natural flavour and demonstrates to be suitable for scaling-up, providing a high potential for practical application.

Cite this article as:

Lozano Pedro, Bernal M. Juana, Lajarin Almudena, Romera Daniel, Garcia-Verdugo Eduardo, Sanchez-Gomez Gregorio, Pucheault Mathieu, Vaultier Michel, Burguete Isabel M. and Luis V. Santiago, A Green Approach for Producing Solvent-free Anisyl Acetate by Enzymecatalyzed Direct Esterification in Sponge-like Ionic Liquids Under Conventional and Microwave Heating, Current Green Chemistry 2014; 1 (2) . https://dx.doi.org/10.2174/2213346101666131113201434