Ultra-Small Pd(0) Nanoparticles into a Designed Semisynthetic Lipase: An Efficient and Recyclable Heterogeneous Biohybrid Catalyst for the Heck Reaction under Mild Conditions.

David Lopez-Tejedor,Blanca De Las Rivas,Jose M Palomo

doi:10.3390/molecules23092358

Abstract

A novel heterogeneous enzyme-palladium (Pd) (0) nanoparticles (PdNPs) bionanohybrid has been synthesized by an efficient, green, and straightforward methodology. A designed Geobacillus thermocatenulatus lipase (GTL) variant genetically and then chemically modified by the introduction of a tailor-made cysteine-containing complementary peptide- was used as the stabilizing and reducing agent for the in situ formation of ultra-small PdNPs nanoparticles embedded on the protein structure. This bionanohybrid was an excellent catalyst in the synthesis of trans-ethyl cinnamate by Heck reaction at 65 °C. It showed the best catalytic performance in dimethylformamide (DMF) containing 10–25% of water as a solvent but was also able to catalyze the reaction in pure DMF or with a higher amount of water as co-solvent. The recyclability and stability were excellent, maintaining more than 90% of catalytic activity after five cycles of use.

Highlights

The Heck reaction is one of the most studied coupling reactions for its usefulness, allowing the catalytic construction of C–C bonds under relatively mild conditions [1,2]
Ala193 to Cys (Figure 2), without alteration in the properties of the enzyme. This GTLσ-A193C variant was overexpressed in Escherichia coli and purified, which permitted to obtain a high amount of protein. This new enzyme solution was combined with palladium acetate to create a new kind of bionanohybrid; nanocatalysts formed by in situ synthesized palladium nanoparticles in the protein network [18]
We have demonstrated the applicability of a new kind of Pd bionanohybrid in the Heck reaction

Summary

Introduction

The Heck reaction is one of the most studied coupling reactions for its usefulness, allowing the catalytic construction of C–C bonds under relatively mild conditions [1,2]. It has been widely used for the synthesis of a huge spectrum of molecules, natural products, polymers, and pharmaceuticals on both the laboratory and industrial scale. Several metals and a huge range of ligands have been studied as catalysts for the reaction, with palladium (Pd) the preferred metal due to its tolerance to a wide variety of functional groups and ability to form C–C bonds between functionalized substrates, proceeding with stereo and regioselectivity and, usually, with good to excellent yields [2]. Investigation towards palladium-catalyzed Heck reaction has been focused on greener approaches to the reaction, performing it in aqueous media, and being able to recover and reuse the catalyst, which is quite important for industrial purposes [5,6,7,8].

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Results

Conclusion