Sustainable Hydrogenation of Vinyl Derivatives Using Pd/C Catalysts

Abstract

The hydrogenation of unsaturated double bonds with molecular hydrogen is an efficient atom-economic approach to the production of a wide range of fine chemicals. In contrast to a number of reducing reagents typically involved in organic synthesis, hydrogenation with H2 is much more sustainable since it does not produce wastes (i.e., reducing reagent residues). However, its full sustainable potential may be achieved only in the case of easily separable catalysts and high reaction selectivity. In this work, various Pd/C catalysts were used for the liquid-phase hydrogenation of O-, S-, and N-vinyl derivatives with molecular hydrogen under mild reaction conditions (room temperature, pressure of 1 MPa). Complete conversion and high hydrogenation selectivity (>99%) were achieved by adjusting the type of Pd/C catalyst. Thus, the proposed procedure can be used as a sustainable method for vinyl group transformation by hydrogenation reactions. The discovery of the stability of active vinyl functional groups conjugated with heteroatoms (O, S, and N) under hydrogenation conditions over Pd/C catalysts opens the way for many useful transformations.

Comparing Separation vs. Fresh Start to Assess Reusability of Pd/C Catalyst in Liquid‐Phase Hydrogenation

“…Liquid‐phase hydrogenation of the selected vinyl derivatives in the presence of Pd/C catalyst at room temperature (22 °C) and a hydrogen pressure of 10 bar proceeded selectively to produce only the corresponding ethyl derivatives (Scheme 1). Thus, there were no side reactions with the solvent, which is consistent with our previous results on the hydrogenation of vinyl derivatives in the presence of various T900‐supported palladium catalysts [39] …”

“…Aqueous ethanol (96 %) and benzene (>99 % purity) were used as received. The Pd/C catalyst, namely, 2.0 % Pd‐PHCs/T900, was prepared by the deposition of Pd II polynuclear hydroxo complexes (PHCs) on carbon black T900 followed by reduction with sodium formate, as described earlier [39] …”

“…The HR‐ESI mass spectra were recorded on a Shimadzu LCMS‐9030 Q‐TOF electrospray ionization mass spectrometer. To determine the product yields, the reaction solutions were analyzed by GC on a GKh‐1000 (Khromos) instrument equipped with a flame ionization detector and a ValcoBond VB‐Wax capillary column (60 m×0.32 mm, polyethylene glycol, stationary phase thickness 0.50 μm) for determination of BVE hydrogenation products and an Agilent DB‐1 capillary column (100 m×0.25 mm, dimethylpolysiloxane, stationary phase thickness 0.50 μm) for determination of DVS and 9‐VC hydrogenation products [39] …”

“…TEM images of the fresh and spent catalyst samples were taken by a JEM‐2100 (JEOL) instrument with a lattice resolution of 0.145 nm. The average size of Pd nanoparticles (NPs) was determined by measuring the size of more than 150 NPs, as described elsewhere [39,43] …”

“…In the present work, we carried out a dedicated comparison of two procedures for testing the reusability of a Pd/C catalyst in liquid‐phase hydrogenations of O‐, S‐, and N‐vinyl derivatives with molecular hydrogen. These reactions represent a good model system [39] and involve heteroatoms with different binding abilities and potential poisoning properties of meal centers.…”