Adams catalyst synthesis

Oxidation of the hexahydro to tetrahydro derivatives was mentioned in connection with the synthesis of 3,5-dioxo-l,2,4-triazines (e.g., Section II,B,2,a). The reverse procedure, hydrogenation of the tetrahydro derivatives, was used with 6-azauracil, 6-azathymine, and their iV-methyl derivatives. With all these compounds hydrogenation proceeds smoothly in the presence of Adams catalyst. Only the hydrogenation of l-methyl-6-azathymine was not successful. ... 

Phenylethylamine has been made by a number of reactions, many of which are unsuitable for preparative purposes. Only the most important methods, from a preparative point of view, are given here. The present method is adapted from that of Adkins,1 which in turn was based upon those of Mignonac,2 von Braun and coworkers,3 and Mailhe.4 Benzyl cyanide has been converted to the amine by catalytic reduction with palladium on charcoal,5 with palladium on barium sulfate,6 and with Adams catalyst 7 by chemical reduction with sodium and alcohol,8 and with zinc dust and mineral acids.9 Hydrocinnamic acid has been converted to the azide and thence by the Curtius rearrangement to /3-phenyl-ethylamine 10 also the Hofmann degradation of hydrocinnamide has been used successfully.11 /3-Nitrostyrene,12 phenylthioaceta-mide,13 and the benzoyl derivative of mandelonitrile 14 all yield /3-phenylethylamine upon reduction. The amine has also been prepared by cleavage of N- (/3-phenylethyl) -phthalimide 15 with hydrazine by the Delepine synthesis from /3-phenylethyl iodide and hexamethylenetetramine 16 by the hydrolysis of the corre-... 

Two diastereomers of 5,10-dideaza-5,6,7,8-tetrahydrofolic acid, DDATHF, 127, both potent inhibitors of folate metabolism and de novo purine synthesis , have been synthesized by catalytic reduction of the unsaturated intermediate diethyl 2-acetyl-5,10-dideaza-9,10-didehydrofolate with Adams catalyst and carrier-free tritium gas in AcOH and H20 solution. Each of the separated (6R) and (6S) diastereomers had specific activity 11.2 Ci mmol and contained tritium almost exclusively at the metabolically stable positions Cjj, C, C J, C gp C o, and the phenyl ring of DDATHF. 

Aminocyclitols are oxidized if they have axial hydroxyl groups, and here, again, the axial hydroxyl groups are attacked. The sensitive amino group must be protected during the oxidation—conveniently, by means of a ben-zyloxycarbonyl group. He3ms and Paulsen i catalytically oxidized iV-ben-zyloxycarbonyl-DL-myo-inosamine-4 (74r-75) to iV-benzyloxycarbonyl-DL-2-keto-mj/o-inosamine-4 (76-77) in the presence of Adams catalyst this constituted the first synthesis of a cyclic amino ketone. This reaction is an important step in the streptamine syntheas devised by these authors. 

Scheme 2.8 First synthesis of 33. Reagents and conditions a) Me2S04, Na2C03, H2O, 80°C, 0.5 h, 33% b) BnCl, Nal, Na2C03, acetone, reflux, 8 h, 81% c) Se02, xylene, reflux, 6 h, 59% d) HCl, EtOH, (EtO)3CH, it to 50°C then it, 89% e) H2, Adams catalyst, EtOAc, rt, 88% f) AC2O, pyridine, 86% g) LiAlH4, Et20, reflux, 4 h then HCl, 50%...

The general picture becomes even more intricate at elevated temperatures. When O-methylflavinantine (18) was treated with BFg-ether in refluxing benzene and the resulting mixture immediately reduced with Adams catalyst, four compounds were isolated, namely thaliporphine (3) (28%), predicentrine (21) (87o), 2,9,10-trimethoxy-3-hydroxyaporphine (24) (367,), and erybidine (19) (8%), for a total overall yield of 80%. The synthesis of the four products can thus be written as in Scheme 10.3. ... 

A novel preparative synthesis of aporphines which should prove of appreciable utility in the future involves the cathodic cyclization of a l-(o-iodo-benzyl)isoquinoline methiodide salt. Gottlieb and Neumeyer have shown that electrolysis of l-(o-iodobenzyl)isoquinoline methiodide in dry acetonitrile containing tetraethylammonium bromide, and using a mercury cathode, furnished an 867o yield of the yellow didehydroaporphine which was reduced over Adams catalyst in methanolic hydrochloric acid to produce aporphine hydrochloride. The formation of didehydroaporphine proceeds via two one-electron reduction steps as shown below. 10,11-Dimethoxyaporphine was also prepared by this route. 

To complete the total synthesis of myrrhine 420, we needed an adequate epimerization of the stereocenter of the common intermediate 425. As illustrated in Scheme 12.110, we elected to pursue an aromatization-reduction sequence by treating aza-tricycle 425 with DDQ, and the ensuing pyridinium salt438 was hydrogenated over Adams catalyst in AcOH to give the all-sy aza-tricycle 439 in 54% yield for the two-step protocol as a 2 1 mixture of diastereomers with respect to the ester group. 

A novel synthesis of 2-aminoquinoxalin-3-one 1-oxide has been effected by the hydrogenation of o-nitro-l-cyanoformanilide in ethanol in the presence of Adam s catalyst.- ... 

Using Mossbauer spectroscopy to monitor the formation of p-hematin under in vitro reaction conditions, Adams et al. have demonstrated that the reaction is a psuedo-zero-order process [109]. Such a process is consistent with a mechanism whereby a small concentration of heme is kept soluble via acetate, functioning as a phase-transfer catalyst, in a heme-saturated solution. In the rate limiting step, the soluble heme aggregates to P-hematin, which in turn grows until it precipitates from solution. There are clearly complicated heterogeneous reaction equilibria involved in the aqueous chemical formation of p-hematin. Consequently, it should be emphasized that the detailed mechanistic analysis of the complex solubilization of the species involved in the chemical synthesis... 

N. Villandier, I. Adam, F. Jerome, J. Barrault, R. Pierre, A. Bouchu, J. Fitremann, and Y. Queneau, Selective synthesis of amphiphilic hydroxyalkylethers of disaccharides over solid basic catalysts. Influence of the superficial hydrophilic-lipophilic balance of the catalyst, J. Mol. Catal. A Chem., 259 (2006) 67-77. 

The N-benzylcinchonidinium catalyst 70 was successfully employed by Barrett et al. in the synthesis of (—)-preussomerin G [112]. As a key step the epoxide 72 was obtained from the quinone acetal 71 in 81% yield and with 95% ee in the presence of 10 mol% of the ammonium salt 70 (Scheme 10.15). Adam et al. recently reported the highly enantioselective epoxidation of isoflavones [113]. The best results, i.e. ee up to 98% with essentially quantitative yields, were achieved when... 

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