Hydrogenolysis over nickel

Ethane Hydrogenolysis. Table II summarizes the kinetic results of ethane hydrogenolysis over nickel catalysts on phosphate (15), niobia (6 ), and niobia-silica (9) supports. As a point of jjefer ... 

Table II. Kinetic Results of Ethane Hydrogenolysis over Nickel Catalysts...

It is known that nature and quality of a catalyst carrier material is important to the performance of a catalyst. The carrier impacts the catalytic reaction and process by its chemical, physical or mechanical properties and/or provides co-catalytic function. An example for a typical support effect is the well-investigated standard reaction of ethane hydrogenolysis over nickel or cobalt on different support materials (Figure 1) [1] ... 

Phenol, polyphenols, and cresols yield aromatic hydrocarbons on hydrogenolysis over nickel catalysts at temperatures above 250°C. 

Catalytic hydrogenation of furan to tetrahydrofuran is accompHshed in either Hquid or vapor phase. Hydrogenation of the double bonds is essentially quantitative over nickel catalysts but is generally accompanied by hydrogenolysis over the noble metals. 

Oximes Amines can be prepared by the catalytic hydrogenation— hydrogenolysis of oximes over nickel or noble metal catalysts. Nickel is used usually in the presence of ammonia. Noble metals are used under mild conditions. The stereochemistry of the reaction depends on the circumstances. On Ra-Ni the trans-2-alkylcyclohexylamine (41) was the main product,529 whereas on palladium the cis product (42) was produced (Scheme 4.137).530... 

It is both interesting and important to note that, judged from the behavior of neohexane, hydrogenolysis over platinum, in contrast to nickel, strongly favors rupture of C—CqUart bonds. The mechanistic implications of this will be discussed subsequently. 

Product Distributions from Hydrogenolysis of Propane and n-Hexane over Nickel Film Catalysts ... 

Nickel, Raney nickel and copper chromite are other catalysts suitable for hydrogenation of aldehydes to alcohols with little if any further hydrogenolysis. Benzaldehyde was hydrogenated to benzyl alcohol over nickel [43], Raney nickel [45] and copper chromite [50] in excellent yields. In the last-... 

Improved synthesis by this method has been achieved in order to obtain solenopsin A (Id) more stereoselectively 388). A cis and trans mixture of pyridine derivative 158, obtained from 156 by the Wittig reaction, was reduced by Raney nickel catalyst in the presence of PtOj to yield the m-piperidine (Ic). The Af-nitroso derivative 159, obtained from Ic by treatment with isoamyl nitrite, was treated with potassium rert-butoxide and then subjected to hydrogenolysis over Raney nickel to give a mixture of ( )-solenopsin A (Id, 1 part) and its isomer (Ic, 1 part) (Scheme 3). 

The aromatic C-F bond in 4-fluorobenzoic acid (13) is readily hydrogenolyzed to yield benzoic acid (14) by Raney nickel or cobalt alloys and alkali,117 while the same bond resists hydrogenolysis over palladium on calcium carbonate in the presence of a base.118... 

In the discussion of the fully conjugated systems, it was pointed out that the N—O bond is very easily cleaved by hydrogenolysis. Therefore fused isoxazolidine systems find use in chiral syntheses. Examples of cleavage reactions are demonstrated with LAH for the iV-methylpiperidine derivative (69) (78TL4647), hydrogenolysis over Raney nickel for the isoquinoline (70) (69CB736) and metal in acid solution for the piperidine (71) (78TL2753). 

The 1,3-dioxolane ring is usually inert to catalytic hydrogenation unless forcing conditions are employed. Hydrogenolysis over rhodium or palladium catalysts in the presence of an acid catalyst gives mainly hydroxy ethers as shown in equation (8). Raney nickel cleaves the oxathiolane ring (Scheme 9) and converts 1,3-benzoxathioles into phenol derivatives. 

The 2- and 3-phenyl-substituted alcohols and their ethers show much lower tendencies toward hydrogenolysis than do benzyl-type alcohols and their ethers, and may give high yields of the corresponding saturated compounds even in hydrogenation over nickel catalysts, as seen in the following examples 178... 

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