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Here, we report transfer hydrogenation of nitroarenes to aminoarenes using 2-propanol as a hydrogen source and Ag-containing magnetically recoverable catalysts based on partially reduced graphene oxide (pRGO) sheets. X-ray diffraction and X-ray photoelectron spectroscopy data demonstrated that, during the one-pot catalyst synthesis, formation of magnetite nanoparticles (NPs) is accompanied by the reduction of graphene oxide (GO) to pRGO. The formation of Ag NPs on top of magnetite nanoparticles does not change the pRGO structure. At the same time, the catalyst structure is further modified during the transfer hydrogenation, leading to a noticeable increase of sp carbons. These carbons are responsible for the adsorption of substrate and intermediates, facilitating a hydrogen transfer from Ag NPs and creating synergy between the components of the catalyst. The nitroarenes with electron withdrawing and electron donating substituents allow for excellent yields of aniline derivatives with high regio and chemoselectivity, indicating that the reaction is not disfavored by these functionalities. The versatility of the catalyst synthetic protocol was demonstrated by a synthesis of an Ru-containing graphene derivative based catalyst, also allowing for efficient transfer hydrogenation. Easy magnetic separation and stable catalyst performance in the transfer hydrogenation make this catalyst promising for future applications.

This paper reports the development of robust Pd- and Ru-containing magnetically recoverable catalysts in a one-pot procedure using commercially available, branched polyethyleneimine (PEI) as capping and reducing agent. For both catalytic metals, ∼3 nm nanoparticles (NPs) are stabilized in the PEI shell of magnetite NPs, whose aggregation allows for prompt magnetic separation. The catalyst properties were studied in a model reaction of 4-nitrophenol hydrogenation to 4-aminophenol with NaBH 4 . A similar catalytic NP size allowed us to decouple the NP size impact on the catalytic performance from other parameters and to follow the influence of the catalytic metal type and amount as well as the PEI amount on the catalytic activity. The best catalytic performances, the 1.2 min –1 rate constant and the 433.2 min –1 turnover frequency, are obtained for the Ru-containing catalyst. This is discussed in terms of stability of Ru hydride facilitating the surface-hydrogen transfer and the presence of Ru 4+ species on the Ru NP surface facilitating the nitro group adsorption, both leading to an increased catalyst efficiency. High catalytic activity as well as the high stability of the catalyst performance in five consecutive catalytic cycles after magnetic separation makes this catalyst promising for nitroarene hydrogenation reactions.

Background/AimsThe functional lumen imaging probe (FLIP) device has been used to assess pyloric dysfunction in patients with gastroparesis. We aim to investigate whether varying FLIP catheter positions affect pyloric FLIP measurements. MethodsPatients undergoing endoscopy for chronic unexplained nausea and vomiting (CUNV) or gastroparesis were prospectively enrolled. FLIP balloon was adjusted for 3 positions within the pylorus: (1) proximal position, 75% of FLIP balloon in the duodenum and 25% in the antrum; (2) middle position, 50% in the duodenum and 50% in the antrum; and (3) distal position, 25% in the duodenum and 75% in the antrum. Pylorus cross-sectional area (CSA), intra-bag pressure (P), and distensibility indices (DI) were measured for 30, 40, and 50-mL balloon volumes. Fluoroscopic images were obtained to confirm FLIP balloon geometry. Data was analyzed separately using FLIP Analytic and customized MATLAB software. ResultsTwenty-two patients with CUNV (n = 4) and gastroparesis (n = 18) were enrolled. Pressures were significantly higher in the proximal position compared to the middle and distal positions. CSA measurements were significantly higher at the proximal and middle positions for 30-mL and 40-mL volume compared to the distal position values. DI values were significantly lower at the proximal positions for 40-mL and 50-mL distensions when compared to the middle and distal positions. Fluoroscopic images confirmed increased balloon bending when placed mostly in the duodenum. ConclusionsFLIP balloon position within the pylorus directly affects balloon geometry which significantly affects P, CSA, and DI measurements. Standardized pyloric FLIP protocols and balloon design adjustments are needed for the continued application of this technology to the pylorus.

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