Pearlman catalyst

To a solution of 3-N-benzyl-6-carboxamido-3-N-methylamino-l,2,3,4-tetrahydrocarbazole (1.0 g) in ethanol (100 ml) containing succinic acid (0.39 g), Pearlmans catalyst (1.0 g) was added and the mixture shaken under an atmosphere of hydrogen at 45 psi and 50°C for 2 h. The mixture was filtered (celite pad) and the pad washed thoroughly with ethanol. The combined flitrate and washings were evaporated to dryness, coevaporated with ethanol (3 times 100 ml) and recrystallised from methanol to give the (+)-6-carboxamido-3-N-methylamino-l,2,3,4-tetrahydrocarbazole succinate (1 1) salt, melting point 148°-155°C. 

Pearlman catalyst <67TL1663>. Cleavage of both methyl and benzyl ether linkages in 42 using six molar equivalents of boron tribromide afforded lamellarin H. 

Lemiere and coworkers synthesized the antipicomavirus agent 3-0-Methylquercetin (76). A key transformation was the conversion of acetophenone 61a to 3-methoxyflavone 79. In the event, 61a and 3,4-dibenzyloxybenzoic anhydride (77) were allowed to react at 160 C in the presence of sodium carboxylate 78 to deliver the penultimate intermediate in 78% yield. Debenzylation of 79 in the presence of Pearlman s catalyst delivered the natural product in 99% yield. 

Catalytic hydrogenation of 5-oxy-7,8,9,10-tetrahydro-6a//-pyrido[l,2-a]quinoxalin-6-ylamines 352 over Pearlman s catalyst under 5 atm of H2 in MeOH for 5-7 days at room temperature gave 6,6u,7,8,9,10-hexahydro-5//-pyrido[ 1,2-u]quinoxalines (01EJOC987). 

Catalytic hydrogenation of 2-cyano-l-(2-nitrophenyl)piperidines over Pearlman s catalyst in a low-pressure hydrogenator under 1 atm of hydrogen in dioxane gave cyclic amidine A -oxides 352 (01EJOC987). 

Pearlman s catalyst provided the target compound 67 in 40% yield and 78% ee, completing the first asymmetric synthesis of this compound. 

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. 

JA754>, and -1,6-dione <2003EJ0268> over Pearlman s catalyst and other Pd-catalysts (PdCl2, or Pd/C) provided different (optically active) pipecolic acid derivatives. 

The hexahydro-l//-pyrrolo[2,l-f][l,4]oxazin-l-one 82 (obtained by radical cyclization see Section 11.11.7.3) was transformed into the proline derivative 83 by hydrogenation in the presence of the Pearlman s catalyst and a stoichiometric amount of trifluoroacetic acid (TFA) (Scheme 10). This reaction led with high yield to the disub-stituted proline 83 in an enantiomerically pure form <2003SL1058>. In an analogous approach, the chiral (4/ ,7/ ,8aA)-methyl 6,6-dimethyl-l-oxo-4-phenylhexahydro-l//-pyrrolo[2,l-r-][l,4]oxazine-7-carboxylate 84 was hydrogenated on Pd(OH)2 in the presence of TFA to give enantiomerically pure 5,5-dimethylproline derivatives 85 <2001SL1836> (Scheme 10). 

Deacetylation and catalytic hydrogenation with Pearlman s catalyst, in the absence of any asymmetric catalyst, afforded the serine conjugate 109 in a 6 1 ratio in favor of the desired (L)-isomer. 

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