Raney nickel, preparation

Catalyst preparation. Freshly prepared Raney nickel gives the best results. For other Ni catalysts the preparation method has been shown to be very important [1,4]. 

Ascaridol (166) forms the saturated ciVl,4-diol (179) on catalytic hydrogenation in the presence of colloidal palladium208 or freshly prepared Raney nickel.209 When palladium210 saturated with hydrogen or platinum dioxide211 is used, dihydroascaridole (181) is formed, with retention of the peroxide bridge. K-Na alloys in ether, zinc and zinc chloride in methanol,209 and the hydrogenation in... 

To a 3.5% (w/v) solution of KOH (1 g) in H O (1 mL) and EtOH (29 mL) was added 4-chloro-2,2 -dini-trodiphenylaminc (1 g, 34 mmol) to give a red suspension. Hydrazine hydrate (0.5 g, 0.01 mol) was then added, followed by a suspension of freshly prepared Raney nickel (10 mg) in EtOH (0.5 mL) the mixture was rapidly warmed to rellux point and stirred for 5 min. The mixture was filtered whilst hot. washed with hot EtOH, and the combined filtrates were diluted with II O (250 mL). The preeipitate was extraeted with CHCI3 and the extract was evaporated to dryness the residue was chromatographed [alumina (pH 4.5), toluene] yield 540 mg (74%), mp 131-133"C. 

To the above mercaptoester (3.0 g, 19 mmol) in ethanol (20 ml) is added a wet suspension of freshly prepared Raney nickel [26] in ethanol ( 5 g). The mixture is heated under reflux and monitored by TLC on silica (ethyl acetate). The desulfurization is complete in about 1 h. The suspension is then treated with activated charcoal, filtered (Celite) and washed with a little ethanol, and then the filtrate is rotary evaporated. Recrystallization of the residue from aqueous ethanol gives methyl imidazole-4-carboxylate (1.27g, 53%), ra.p. 149°C. 

Another process for preparing Raney nickel particles of sufficient size for use in a flow reactor involves mixing a Raney alloy powder with a polymer and plasticizer. This mixture is extruded to an appropriate shape, the plasticizer is removed eind the extrudate calcined in air at high temperatures to form an a-alumina matrix to support the alloy. Reaction with base removes some of the surface aluminum to give an active surface of Raney nickel that has been shown to be active for vapor phase and trickle flow hydrogenations. ... 

Izumi and Akabori first invented MNi in 1963. They modified freshly prepared Raney nickel (W-1 type) with a mono-sodium salt of glutamic acid (Gul-MRNi). This catalyst gave a 15% e.d.a. for the hydrogenation of methyl acetoacetate (MAA) to methyl 3-hydroxybutanoate (MHB). It was sheer luck that MAA was employed as the substrate. Even today MAA is one of the best substrates, and it has long been employed as a standard. Immediately after the discovery by Izumi et al, Klabunovskii and coworkers started studies of this type of catalyst, and the groups led by Izumi and Klabunovskii carried out almost all the early research. ... 

Reduction of quinoxaline with sodium in THF at 20° yields a deep-purple solution from which 1,4-dihydroquinoxaline is isolated. Reduction with either sodium in refluxing alcohol or lithium aluminum hydride in ether gives 1,2,3,4-tetrahydroquinoxaline. Hydrogenation of quinoxaline over a 5% rhodium-on-alumina catalyst at 100° and 136 atm or over freshly prepared Raney nickel W-6 under similar conditions gives meso-(cis)-decahydroquinoxaline. ° However hydrogenation of quinoxaline over a palladium-on-charcoal catalyst at 180° and 50 atm gives dl-(/rans)-decahydroquinoxaline." ... 

In more recent work, pyridine, quinoline, and their derivatives have been dimerized with the aid of specially prepared Raney nickel catalyst.301... 

In the hydrogenation of 4-(3-cyano-1-oxopropyl)methylenedioxybenzene in methanol containing freshly-prepared Raney nickel for 8 hours at tOO C, ring closure afforded a 90% yield of 2-(benzo[1,2-d]-[1,3]dioxo-5-yl)pyrroline (ref.96). 

In complete contrast to these results above, insonation of Raney nickel produced a reduction in catalytic efficiency (Table 10.4). The as-supplied material (Type 2, Aldrich) gave 100% conversion after 30 min under conventional conditions compared to only 25% conversion after 30 min after insonation. Due to its method of preparation Raney nickel has a high surface area and considerable porosity. It seems reasonable to conclude that Raney nickel which has been irradiated with ultrasound may agglomerate and consolidate, therefore reducing porosity and hence its catalytic activity. 

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