Schiff bases catalytic hydrogenation

The Schiffs base catalytic hydrogenation rate can be expressed as dC/dt = k [H2]l [Schiff base ]... 

Figure 3 in Scheme 2.3-2 illustrates that Ni- or Pd-complexes prefer a different combination of elementary steps. Here, it is evident that Ni favors 2 1 co- oligomerization of butadiene with tddehyde or of a Schiff base with butadiene involving C -bond formation coupled with metalalogous 1,5-hydrogen transfer. On the other hand, Pd favors 0—C- or N—C- andC—C-bond formation. These processes seem to occur more frequently, as demonstrated by other catalytic processes and model reactions . ... 

J. Zhu, B.A. Price, J. Walker, S.X. Zhao, Catalytic hydrogenation of ethyl 2-amino-2-difluoromethyl-4-cyanobutanoate and its Schiff base reaction modes. Tetrahedron Lett. 46 (2005) 2795-2797. 

Catalytic Hydrogenation of a Schiff s Base over Pd/Carbon Catalysts Kinetic Prediction of Impurity Fate and Byproduct Formation... 

The first step in one synthesis of the antipsychotic dmg clozapine (37-5) involves UUman coupling of anthranUic acid (37-1) with 2,4-dichloronitrobenzene (30-1) to give the substituted anthranilate (37-2). The carboxyl group is then converted to the A-methylpiperazinamide (37-3) via a suitably activated intermediate as, for example, the imidazohde obtained by reaction with carbonyidiimidazole (CDl). The nitro group is then reduced to amine (37-4) by means of catalytic hydrogenation. Intramolecular Schiff base formation catalyzed by toluenesulfonic acid then completes the synthesis of clozapine (37-5) [38]. 

The effect of substituting a chloro, methyl, or ferf-butyl group for the para-hydrogens of the phenyl rings of Schiff base 26 has been studied with regard to their catalytic activities in the oxygenation of... 

Catalytic asymmetric hydrogenation of prochiral Schiff bases has been reviewed.57 (g)... 

Ruthenium compounds are widely used as catalysts for hydrogen transfer reactions. These systems can be readily adapted to the aerobic oxidation of alcohols by employing dioxygen, in combination with a hydrogen acceptor as a cocatalyst, in a multistep process. These systems demonstrate high activity. For example, Backvall and coworkers [146] used low-valent ruthenium complexes in combination with a benzoquinone and a cobalt-Schiffs base complex. Optimization of the electron-rich quinone, combined with the so-called Shvo Ru-cata-lyst, led to one of the fastest catalytic systems reported for the oxidation of secondary alcohols (Fig. 4.59). 

Many other reports of ligand libraries for specific catalytic applications have been reported. Among them, Gilbertson and co-workers reported a chiral phosphine library, tested in the rhodium-catalyzed asymmetric hydrogenation of an enamide (158,159), and a similar library for the palladium-catalyzed allylation of malonates (160, 161) Hoveyda and co-workers (162, 163) reported a chiral Schiff base library, screened in the titanium-catalyzed opening of epoxides with (TMSCN) (trimethyl silyl cyanide) ... 

The substituted perhydro-imidazo[l, 5-uJpyridine (113) was prepared in order to test for inhibition of enzymes thymidylate synthetase and dihydrofolate reductase. Pyridine-2-carboxaldehyde was condensed with ethyl-p-aminobenzoate to give the Schiff base (111) which, on sodium borohydride reduction followed by catalytic hydrogenation, resulted in 112. Condensation of 112 with 5-formyluracil gave 113 (70JMC276). 

Amadori believed that his three stable compounds were all Schiff bases, although he recorded no steps taken to prove their structure. Kuhn and Dansi worked with the stable isomer Amadori had derived from D-glu-cose plus p-toluidine, and showed that it could not be a Schiff base. On catalytic hydrogenation, an unknown dihydro compound of m. p. 195° was isolated whereas, if the stable isomer had been a Schiff base, the known 1-deoxy-l-p-toluidino-D-glucitol, of m. p. 143°, would have been formed. 

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