Crystal facet-dependent upgrading of saccharides over barium peroxide to synthesize C-glycoside ketones

Abstract

Transformation of abundant and easily accessible carbohydrates to high-value chemicals is of the essence in the field of biorefinery. However, selective conversion of unprotected saccharides exists great challenges regarding the peculiarity of multi-functional groups. Herein, barium peroxide (BaO2) with preferential crystal facet presented an excellent performance in the direct Knoevenagel condensation of various saccharides with acetylacetone for the synthesis of C-glycoside ketones. Characterization methods including XRD, TG-DSC, Raman spectra, SEM and TEM revealed that commercial barium oxide (BaO) calcinated under air atmosphere could react with oxygen to generate the new species of BaO2. Moreover, the relative proportion of each crystal facet of BaO2 could be controlled by regulating the calcination condition. And BaO2 with (110) facet exhibited better reactivity than that with dominant (002) crystal facet. Combining the results of experiment and DFT calculation, it’s revealed that the different adsorption energies of substrates on diverse crystal facets could modulate the reaction path and the construction of C-C bonds would proceed efficiently on BaO2(110) facet. This work has developed a convenient and practical procedure to prepare BaO2 with preferential crystal facet which could be used as a novel solid base catalyst for sustainable upgrading of carbohydrate platforms.