Hydrogenolysis catalytic

The amino group of the A-benzyloxycarbonyl derivative is protected as the amide half of a carbamate ester (a urethane, Section 21-16), which is more easily hydrolyzed than most other amides. In addition, the ester half of this urethane is a benzyl ester that undergoes hydrogenolysis. Catalytic hydrogenolysis of the A-benzyloxy carbonyl amino acid gives an unstable carbamic acid that quickly decarboxylates to give the deprotected amino acid. 

Removal of halogen from aromatic rings can also be accomplished by various reducing agents, among them BusSnH, " catalytic hydrogenolysis, " catalytic transfer hydrogenolysis, ... 

A further noteworthy although not yet exploited blocking is the alkylation of the cysteine side chain with the p-nitrobenzyl group. While it is acid resistant and can not be cleaved by hydrogenolysis, catalytic hydrogenation converts it to the p-aminobenzyl group which is then smoothly removed by salts of divalent mercury, such as Hg acetate ... 

Engstrom J R, Goodman D Wand Weinberg W H 1986 Hydrogenolysis of n-butane over the (111) and (110)-(1 2) surfaces of iridium a direct correlation between catalytic selectivity and surface structure J. Am. Chem. Soc. 108 4653... 

Hydrogenolysis refers to the cleavage of a molecule under conditions of catalytic hydrogenation... 

Hydrogen bromide may be used to remove either the benzyloxycarbonyl or tert butoxycarbonyl protecting group The benzyloxycarbonyl protect mg group may also be removed by catalytic hydrogenolysis... 

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. 

Procter Gamble catalytic hydrogenolysis coconut and palm kernel oils, taLow, palm oil c c... 

The first commercial production of fatty alcohol ia the 1930s employed the sodium reduction process usiug a methyl ester feedstock. The process was used ia plants constmcted up to about 1950, but it was expensive, hazardous, and complex. By about 1960 most of the sodium reduction plants had been replaced by those employing the catalytic hydrogenolysis process. Catalytic hydrogenation processes were investigated as early as the 1930s by a number of workers one of these is described ia reference 26. 

Tri-, Tetra-, and Pentafluoropyridines. 2,4,6-Trifluoropyridine can be prepared in 75% yield by catalytic hydrogenolysis (paHadium-on-carbon, 280°C) of 3,5-dichloro-2,4,6-trifluoropyridine [1737-93-5] (416). The latter is synthesized by exchange fluorination of pentachloropyridine with potassium fluoride in polar solvents such as /V-methy1pyrro1idinone (417,418). 3,5-Dichloro-2,4,6-trifluoropyridine is used to... 

The isolation of the 6-deoxytetracyclines (44) led to other chemical modifications of (1). 6P-Deoxytetracycline [5614-03-9] (13), prepared by catalytic hydrogenolysis of tetracycline (1), resulting ia an iaversion (45) of the configuration at the C-6 position, but retention of antibacterial activity. Catalytic reduction (7,8) of the 6-methylene derivative (14) yields both the 6a-methyl (15) and 6P-methyl compound (13). The 6a-isomer (15) is reported (7,45) to be more active than the 6P isomer (13). The a-isomer, doxycycline (6), is an example of a semisynthetic tetracycline that has become commercially useful. 

The catalysts with the simplest compositions are pure metals, and the metals that have the simplest and most uniform surface stmctures are single crystals. Researchers have done many experiments with metal single crystals in ultrahigh vacuum chambers so that unimpeded beams of particles and radiation can be used to probe them. These surface science experiments have led to fundamental understanding of the stmctures of simple adsorbed species, such as CO, H, and small hydrocarbons, and the mechanisms of their reactions (42) they indicate that catalytic activity is often sensitive to small changes in surface stmcture. For example, paraffin hydrogenolysis reactions take place rapidly on steps and kinks of platinum surfaces but only very slowly on flat planes however, hydrogenation of olefins takes place at approximately the same rate on each kind of surface site. 

Catalytic hydrogenolysis of an O-benzyl protective group is a mild, selective method introduced by Bergmann and Zervas to cleave a benzyl carbamate (> NCO—OCH2C6H5 > NH) prepared to protect an amino group during pep-... 

Catalytic transfer hydrogenation (entries 2 and 3 below) can be used to cleave benzyl esters in some compounds that contain sulfur, a poison for hydrogenolysis catalysts. 

This is the oxidized form of the methylthio derivative above. It is stable to catalytic hydrogenolysis and does not poison the catalyst. It is stable to liquid HF (30 min), but is cleaved in 5 s with 1 N NaOH. ... 

Catalytic Hydrogenolysis of Carbon-Huonne Bonds it-Bond Participation Mechamsm Hudlicky, M J Fluorine Chem 44, 345-359 58 n o C) S ... 

Catalytic hydrogenation in acetic anhydride-benzene removes the aromatic benzyl ether and forms a monoacetate hydrogenation in ethyl acetate removes the aliphatic benzyl ether to give, after acetylation, the diacetate. Trisubstituted aDcenes can be retained during the hydrogenolysis of a phenolic benzyl ether. ... 

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