Highly Selective and Multigram Hydrogenation of Citral into Citronellal by Palladium Nanoparticles in Water

Abstract

The synthesis of citronellal, an added-value chemical for perfumery, was performed through selective and green hydrogenation of citral into citronellal in water. Aqueous suspensions of spherical ammonium-capped palladium nanoparticles with sizes around 3 nm selectively reduced the conjugated carbon–carbon double bond. An excellent selectivity up to 97% in citronellal was achieved at complete conversion in water. The presence of potassium hydroxide proved crucial to control the selectivity and avoid other hydrogenation coproducts. These optimized conditions were further applied to a 135 g substrate loading, affording a relevant turnover number (TON) of 10,000.

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