B-Containing Hydrotalcites Effectively Catalyzed Synthesis of 3-(Furan-2-yl)acrylonitrile Derivatives <i>via</i> the Knoevenagel Condensation
Sonia Mancípe, Juan‐Carlos Castillo, María H. Brijaldo, Viviana P. López, Hugo Rojas, Mario A. Macías, Jaime Portilla, Gustavo P. Romanelli, José J. Martínez, Rafael Luque
Abstract
5-Hydroxymethylfurfural (HMF) is a well-known platform chemical derivative from biomass. Herein, we described the application of boric acid deposited on hydrotalcite as a catalyst in the Knoevenagel reaction of HMF derivatives and active methylene compounds to afford new HMF derivatives containing an acrylonitrile moiety under solvent-free conditions. The boric acid incorporation method on hydrotalcite conditioned the yields obtained because the aluminum substitution by boron atoms can modify the acidity of these solids. The Knoevenagel adduct structure (3a) was studied and confirmed by X-ray crystallography. This protocol synthesis features operational simplicity, short reaction times, high yields, good to excellent (E)-isomer selectivity, and low catalyst loading. Remarkably, the catalyst could be simply recovered and reused up to five cycles without appreciable loss of catalytic activity.