Organocatalytic continuous flow strategies for the upgrading of biobased molecules

Organocatalyzed transformations for the upgrading of biomass-derived molecules are studied under continuous flow conditions. Both on- and off-line analytical tools are implemented for reaction monitoring and product quantification. We will first present our efforts for the development of a continuous process for the carbonation of 3-butene-1,2-diol toward vinyl ethylene carbonate. Both homogeneous and polymer-supported 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) are studied as organocatalysts. The carbonation reaction is amenable to both purified or crude 3-butene-1,2-diol derived from erythritol. Aiming at a broader substrate scope, the carbonation procedure is next extended to glycerol and other biobased diols. Libraries of homogeneous and heterogeneous organocatalysts are screened, emphasizing that homogeneous and polymer-supported phosphazene and guanidine superbases are efficient catalysts under solvent-free conditions. To further improve cost-efficiency, cheap organic salts such as ammoniums and phosphoniums are assessed as well, giving slightly improved yields by comparison to organic superbases, although requiring more drastic process conditions. In the last part of this lecture, we will illustrate our efforts in photocatalytic continuous flow procedures for the upgrading of biobased fumaric and itaconic acids. γ-Butyrolactones, including spiro derivatives, are produced in good yields under 365 nm LED irradiation and in the presence of benzophenone as a cheap photosensitizer.