Greener Methodology: An Aldol Condensation of an Unprotected C‑Glycoside with Solid Base Catalysts
journal contributionposted on 27.04.2018, 00:00 by Tamara M. de Winter, Laurène Petitjean, Hanno C. Erythropel, Magali Moreau, Julien Hitce, Philip Coish, Julie B. Zimmerman, Paul T. Anastas
The development of a new enamine-solid-base-catalyzed (ESBC) methodology for the aldol condensation reaction is reported. Solid base catalysts [nonactivated and activated magnesium oxide (MgO and MgOact) and calcium oxide (CaO and CaOact), a hydrotalcite (HT), and a porous metal oxide (PMO)] were investigated as safer and greener alternatives to previously reported catalytic systems. Multiple reaction parameters (temperature, solvent, time, and catalyst loading) were investigated todetermine optimal conditions for the practitioner to employ in the synthesis of C-glycosides. The optimized reaction conditions provided highly functionalized (E)α,β-unsaturated ketones from unprotected C-glycosides in good to excellent yields. Moreover, the ESBC methodology is applicable to a wide range of aromatic aldehydes that feature electron-rich and electron-poor moieties, as well as sterically bulky groups. Lastly, the recyclability of the MgO catalyst was demonstrated.