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Selective hydrogenation of α,β-unsaturated aldehydes to unsaturated alcohols is important for the synthesis of fine chemicals, yet very challenging. Herein, we reported a metal-free CeO2 nanorods (r-CeO2) catalyst for gas-phase transformation of crotonaldehyde to crotyl alcohol with the highest selectivity of 93.2% at 323 K. Compared to CeO2 nanocubes and nanopolydra, r-CeO2 shows a much higher crotyl alcohol production rate, comparable turnover frequency to those of noble-metal-based catalysts, and very high crotyl alcohol selectivity. This can be associated with a relatively high density of surface oxygen vacancies on r-CeO2, which constructs the solid frustrated Lewis pair sites with enhanced heterolytic H2 dissociation and preferred crotonaldehyde adsorption via the CO bond. However, a further reduction of r-CeO2 by H2 was observed to be unfavorable with regard to both catalytic activity and selectivity, because of the emergence of crotonaldehyde adsorption via the CC bond. These findings provide a potential approach to fabricate high-performance and low-cost catalysts for selective hydrogenation of α,β-unsaturated aldehydes to unsaturated alcohols using bare CeO2 with a rigid surface structure design.

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Abstract:The asymmetric synthesis of functionalized 2-amino-2-chromene derivatives with high enantioselectivities via one-pot tandem reactions of functionalized a,b-unsaturated ketones with malononitrile catalyzed by 9-amino-9-deoxyepiquinine (1a) in combination with (R)-1,1'-binaphth-2,2'-diyl hydrogen phosphate (1c) is reported for the first time.