Control of selectivity in hydrosilane-promoted heterogeneous palladium-catalysed reduction of furfural and aromatic carboxides

Abstract

The production of liquid fuels and fine chemicals often involves multi-step reaction processes with selective hydrogenation as one of the key steps. This step most often depends on highpressure excess hydrogen gas, fossil resources, and newly prepared metallic catalysts. Here we describe an approach to tune activity and selectivity toward transfer hydrogenation of renewable biomass derivatives over commercially available Pd/C using liquid hydrosilane as hydrogen source. The appropriate control of water-doping content, acid type, reaction temperature, and liquid H − donor dosage permits the selective formation of four different value-added products in high yields (≥90%) from bio-based furfural under mild reaction conditions (15-100°C). Mechanistic insights into the hydrosilane-mediated cascade reactions of furfural are obtained using isotope labeling. The catalyst is recyclable and can selectively reduce an extensive range of aromatic carbonyl compounds to the corresponding alcohols or hydrocarbons in 83-99% yield, typically at 25-40°C.

Carbonate-Catalyzed Room-Temperature Selective Reduction of Biomass-Derived 5-Hydroxymethylfurfural into 2,5-Bis(hydroxymethyl)furan

“…The aldehydic proton 1a of HMF gradually disappeared, while the protons of hydroxyl 2c and methine of the furan ring 2a of BHMF were also detected and significantly enlarged by further extending the reaction duration. The mechanism for the hydrogenation of aldehydes or ketones catalyzed by K2CO3 was thus proposed to be very similar to the reduction process of amides [53], where Ph2SiH2 might act as an H-donor to promote the reduction of HMF to BHMF, as demonstrated by in situ NMR in our previous study [39]. The possible reaction mechanism of the hydrogenation of HMF to BHMF is shown in Scheme 1.…”

“…Hydrosilylation of carbonyl compounds to siloxanes shows great potential in the selective synthesis of alcohols [34,35]. This type of conversion process is very attractive because the used silanes are a water-and air-stable hydrogen source, which is able to be stimulated by metal-containing catalysts under mild conditions [22,[36][37][38][39][40]. In addition, the strongly basic solvent used was proposed to facilitate its coordination with the catalytically active species (e.g., carbonate) [41], which is favorable for the reaction with silane to release hydride.…”

Highly Selective Reduction of Bio-Based Furfural to Furfuryl Alcohol Catalyzed by Supported KF with Polymethylhydrosiloxane (PMHS)

“…e Meerwein-Ponndorf-Verley (MPV) reduction which is used alcohol as liquid H-donor has been largely applied in the reduction of biomass platform molecules, which can simultaneously produce two useful compounds and thus attracts the attention of numerous researchers focusing on biomass valorization [42][43][44]. Generally, the catalysts performing high catalytic activity for the MPV reduction of FUR to FFA include acid-base bifunctional catalysts (e.g., Pd/HZSM-5 and MgO-Al 2 O 3 ) [45,46] and Lewis acid catalysts (e.g., Al-, Zr-zeolites, and Zr-, Al-, Hf-based catalysts) [47][48][49].…”

Heterogeneous Catalytic Upgrading of Biofuranic Aldehydes to Alcohols

“…Over the past several decades, different types of heterogeneous catalysts and advanced methods have been explored to catalyze the hydrogenation of bio-based furanic aldehydes to alcohols (Chen et al, 2014a). Several research groups are currently studying this reaction using various noble metals, such as Pd (Audemar et al, 2014; Li et al, 2018c), Pt (An et al, 2013; Shi et al, 2016), and Ru (Nishimura et al, 2014; Yuan et al, 2015b), non-noble metals, such as Cu (Lesiak et al, 2014; Upare et al, 2018) and ferrous metals (Fe, Ni, Co) (Yao et al, 2014; Yu et al, 2015; Halilu et al, 2016), solid acid-base catalysts, and alkali metal salt catalysts [e.g., K 2 CO 3 (Long et al, 2018), Cs 2 CO 3 (Long et al, 2019) and KF (Wu et al, 2018; Zhao et al, 2018)] for the catalytic upgrading of biomass-derived furanic aldehydes to alcohols.…”