Reaction debenzylation

Pterin, 7-chloro-reduction, 3, 293 Pterin, 6-chloromethyl-synthesis, 3, 312 Pterin, 5,8-diacetyl-5,8-dihydro-synthesis, 3, 306 Pterin, N, N -dibenzyl-debenzylation, 3, 295 Pterin, 6-(dibromomethyl)-synthesis, 3, 302 Pterin, 6-(diethoxymethyl)-synthesis, 3, 312 Pterin, 6,7-dihydro-quinonoid, 3, 306 Pterin, 7,8-dihydro-electrochemistry, 3, 285 quaternization, 3, 305 reactions... 

Tetrahydro-y-carbolines may be prepared by an internal Mannich-type reaction between 2-j8-aminoethyhndoles and formaldehyde. Kebrle et al. prepared 27 by the reaction of 2-lithio-l-methyl-indole with A-benzyl-A-ethylaminoacetone followed by debenzyl-ation treatment of 27 with formaldehyde led to the formation of the tetrahydro-y-carboline 28. Similarly, when the quaternary salts (30) of the Mannich bases (29) are heated at 100°, 1,2,3,4-tetrahydro-y-carbohnium salts (31) are formed. 

Vilsmeier-Haack and Friedel-Crafts reactions, bromination, debromination, debenzylation in indole series and their synthetic application 99YZ35. 

The reaction of methane tricarboxylate with indoline 342 gave the tricyclic derivative 361 which can be transformed to the amide derivatives 362 (97JHC969). Alkylation of the iV-benzyl indoline 360 with pentafluor-oacetone gave 363 which upon debenzylation and subsequent acylation with diketene followed by cyclization gave 364. Other haloacetones were used to prepare different halogenated derivatives (79BEP872311) (Scheme 63). 

Choice of catalyst and solvent allowed considerable flexibility in hydrogenation of 8. With calcium carbonate in ethanol-pyridine, the sole product was the trans isomer 9, but with barium sulfate in pure pyridine the reaction came to a virtual halt after absorption of 2 equiv of hydrogen and traws-2-[6-cyanohex-2(Z)-enyl]-3-(methoxycarbonyl)cyclopentanone (7) was obtained in 90% yield together with 10% of the dihydro compound. When palladium-on-carbon was used in ethyl acetate, a 1 1 mixture of cis and trans 9 was obtained on exhaustive hydrogenation (S6). It is noteworthy that in preparation of 7 debenzylation took precedence over double-bond saturation. 

Quebrachitol was converted into iL-c/j/roinositol (105). Exhaustive O-isopropylidenation of 105 with 2,2-dimethoxypropane, selective removal of the 3,4-0-protective group, and preferential 3-0-benzylation gave compound 106. Oxidation of 106 with dimethyl sulfoxide-oxalyl chloride provided the inosose 107. Wittig reaction of 107 with methyl(triphenyl)phos-phonium bromide and butyllithium, and subsequent hydroboration and oxidation furnished compound 108. A series of reactions, namely, protection of the primary hydroxyl group, 0-debenzylation, formation of A-methyl dithiocarbonate, deoxygenation with tributyltin hydride, and removal of the protective groups, converted 108 into 7. 

The key intermediate in another total synthesis of secoquettamine (234), elaborated by Stevenson et al. (185), was 2-arylbenzofuran 241 prepared by a coupling reaction of the copper salt of 4-benzyloxyphenylacetylene with bromoisovanillin (Scheme 37). In the next step condensation with nitro-methane and reduction gave amine 242, which when N-methylated and debenzylated resulted in secoquettamine (234). 

The new DeLink 3%Pd/CPS4 catalyst has been tested for debenzylation of N-phenylbenzylamine also. Under the same reaction conditions, 3%Pd/CPS4 has approximately the same activity as the current commercially produced 5%Pd/CPS2 in this N-debenzylation reaction on catalyst weight basis. 

Pd/CPS4 catalyst without using inhibitor (12). As shown in Figure 3, the reaction requires selective debenzylation versus dehalogenation of the... 

S. Y Wang, and J. P. Chen et al., Selective Debenzylation in the Presence of Aromatic Chlorine on Pd/C Catalysts Effects of Catalyst Types and Reaction Kinetics , paper presented at 20th Organic Reactions Catalysis Society Meeting, March 21-25, 2004, Hilton Head Island, SC, USA. 

In addition to the already known inhibiting effect of N-containing bases on debenzylation reactions we have shown that similar modifiers can increase the rate of hydrogenolysis of a CBz protected amino acid. As these reactions are carried out on industrial scale the addition of certain modifiers can increase the reaction rate, thus leading to shorter reaction times and higher productivity. 

Selective Debenzylation in the Presence of Aromatic Chlorine on Pd/C Catalysts Effects of Catalyst Types and Reaction Kinetics... 

Table 1 Catalytic performance of the debenzylation reaction on different types of supported palladium catalyst. ...

In order to select a suitable catalyst, a variety of Pd/C catalysts were screened. Table 2 shows that the dechlorinated by-product was minimized to the level less than 1% as the catalyst metal loading increased from 3% to 10%. The catalytic activity for the debenzylation reaction was examined and compared based on the rate of hydrogen uptake (Figures 1 and 2). 

Cyclic phosphonate analogues of hexopyranoses were debenzylated in MeOH-H20 on Pd/C. The system was purged with H2, and the reaction was run under 1 atm of H2 while being stirred vigorously. The reaction was complete after 12 hours. On the other hand, when sodium iodide in acetonitrile... 

---