Insights into the ruthenium-catalysed selective reduction of cardanol derivatives via transfer hydrogenation: a density functional theory study?

Catalysis Science & Technology Pub Date: 2023-02-27 DOI: 10.1039/D3CY00135K

Abstract

The detailed mechanism for ruthenium-catalysed selective reduction of cardanol derivatives by transfer hydrogenation has been fully characterised at the B3PW91-D3/ECP2/PCM//B3PW91/ECP1 level of density functional theory. The explored catalytic cycle involved the hydrogenation of the triene cardanol giving the diene product through a highly stable η3-allylic intermediate via a kinetic barrier of 29.1 kcal mol?1, which followed further hydrogenation leading to a more stable η3-allylic intermediate. The further reduction to the cardanol monoene product required an overall barrier of 29.2 kcal mol?1, which offers a rationale for the requirement of elevated temperatures (refluxing isopropanol). The computed overall barrier of 46.6 kcal mol?1 to accommodate a fully saturated product is unsurmountable—in good agreement with the experiment, where no such full hydrogenation is observed, and rationalising the 100% selectivity towards the monoene product.

Graphical abstract: Insights into the ruthenium-catalysed selective reduction of cardanol derivatives via transfer hydrogenation: a density functional theory study
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