PEARLMAN Hydrogenolysis Catalyst

Palladium catalysts, mostly palladium on carbon and Pearlman s catalyst, are used for the hydrogenolysis of the benzyl—nitrogen bond. However, in some cases, platinum, nickel, and copper chromite catalysts have also been used. 

Further elaboration of the sulfur cycloadducts could be achieved by the use of a Pummerer rearrangement in the syntheses of 5-(hydroxymethyl)prolines. Oxidation of adduct 298 to sulfoxide 299, followed by treatment with TEA in DCM and quenching with either methanol or benzyl alcohol, delivered the Pummerer products 300 in 57% yield for R = Me and 38% for R = Bn as single diastereoisomers. Raney Ni desulfurization and Pearlman s catalyst mediated hydrogenolysis, for R = Bn furnished the final enantiopure proline derivative (Scheme 3.99). 

Hydrogenolysis of BOM ethers in the presence of alkenes is passible using Pearlman s catalyst [Pd(OH)2/C].504 For example a BOM group was removed... 

The nonpyrophoric PdfOHjj/C (Pearlman s catalyst) catalyzes the selective hydrogenolysis of benzylamines in the presence of benzyl ethers. ... 

Furthermore, the isopropylated product has been converted into a-amino acid (Scheme 7.19) through cleavage of the N-N bond of the diaster-eochemically pure product by hydrogenolysis in the presence of Pearlman s catalyst. In earlier work on triethylborane-induced radical reactions in organic solvents, oxime ether showed excellent reactivity. Thus we expect that the direct comparison of indium-mediated reactions with triethylborane-induced reactions would lead to informative and instructive suggestions regarding the reactivity and stereochemical course of the transformation in question. 

The CTFB group was developed to be orthogonal to the 2-naphthyl carbamate. Benzyl esters and aromatic benzyl ethers can also be reduced in its presence. It is introduced via the chloroformate. It is cleaved by hydrogenolysis with Pd-C in sluggish cases, Pearlman s catalyst should be used. It can be cleaved without reduction of an aromatic nitrile group. 

Palladium catalysts, usually Pearlman s catalyst [42] and Pd/C are used for the hydrogenolysis of benzyl-nitrogen bonds. Acetic acid, ethyl acetate, ethanol, or methanol are frequently used as solvents. Sometimes a small amount of a strong acid is added to the reaction mixture [54-56]. The bond rupture needs the adsorption of carbon [57]. The hydrogenolysis of C-N bonds occurs with inversion on both Pd and Ni [2,58]. 

Catalytic hydrogenolysis of 6,1 l-dihydrodibenzo[6,/][l,4]dioxocin (138 R = H) over Pearlman s catalyst affords catechol in 99% yield, suggesting the possible utility of such derivatives as protecting groups for 1,2-diols l,2,3,4,4a,6,ll,12a-octahydrodibenzo[Z>/][l,4]dioxocin (154) is similarly converted to cyclohexanediol <89SC3363>. 

This strategy, which involves two concomitant hydroformylation reactions of vinyl groups present on the same molecule, had never previously been used in total synthesis. Reduction of 5-azidononanedial 45h by hydro-genolysis in the presence of Pearlman s catalyst led to the formation of norlupinane, in a hydrogenolysis/bis-reductive amination tandem process, in quantitative yield (Scheme 19). This success allowed us to consider the synthesis of non-racemic mcmosubstituted quinolizidines such as (+)-lupinine and (+)-epiquinamide. 

Two total syntheses of pyrrolidine alkaloids have been reported. (—)-Codonopsinine (85), an imino-pentitol which exhibits antibiotic and hypotensive activity, has been synthesized in seven steps in 16% overall yield from dihydropyrrole 84. The enantioselective synthesis of the potent antifungal agent (-l-)-preussin (87) has also been achieved from L-phenylalanine derivative 86. The pyrrolidine skeleton was established by hydrogenolysis of an intermediate oxazoline and subsequent diastereoselective reductive cyclization of the resultant aminoketone using Pearlman s catalyst. ... 

A Wittig reaction of the ylide 294 with the aldehyde 289 formed the backbone 295, which was then treated with trifluoroacetic acid to remove the acetonide, followed by acylation of the diol with the (-)-TCA segment 296 (248). Hydrogenatirai of the alkene and hydrogenolysis of all benzyl protecting groups with H2 (1 atm) and Pearlman s catalyst afforded fumonisin B2 (250) (Scheme 5.6). 

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