Hydrogenation of N-heterocyclics

Hydrogenation of N-heterocycles, metallocomplex catalysts in 85UK289. Ionic hydrogenation of N-heterocycles 79KFZ(8)75. 

Hydrogenation of N-heterocycles -Hydrogenation of arene rings -Hydrogenolysis and cleavage of C-N bonds... 

Other ligand environments (e.g. cyclopentadienyl or phosphine metal complexes) have proved more adequate for detailed investigations of the hydrogenation of N-heterocycles. The groups of Fish [91], Sanchez-Delgado [99] and Rosales [100] have provided extensive studies including kinetic data, deuteration experiments, detailed NMR studies, isolation of important intermediates, and some theoretical calculations. 

From the examples described in the preceding Sections and in Chapter 3, Section 3.3.2 (p. 84), it can be concluded that the hydrogenation of N-heterocyles is much more facile than C-N bond breaking reactions when soluble transition metal complexes are employed as models for HDN catalysis this is in parallel to what has been observed on metal sulfide surfaces. Indeed, while several examples of efficacious homogeneous catalysts for the hydrogenation of N-heterocycles to the corresponding cyclic amines (partially or fully saturated) are available (see Chapter 3), only one case of C-N bond hydrogenolysis promoted by a metal-complex in solution has been described so far. Moreover, the real nature of this process is not clearly defined. 

Table 3.2. Homogeneous catalysts for the hydrogenation of benzothiophene. 78 Table 3.3. Homogeneous catalysts for the hydrogenation of N-heterocycles. 86...

Selective hydrogenation of N-heterocycles— N-acylation s. 17, 76 Ring hydrogenation with... 

Rhodium-alumina/ammonia Ring hydrogenation of N-heterocyclic carboyxlic acids... 

Rhodium-alumina/acetic acid Hydrogenation of N-heterocycles... 

Platinum oxide hydrogen chloride Hydrogenation of N-heterocycles s. 18, 559... 

Ring hydrogenation of imidazoles Selective hydrogenation of N-heterocycles Ring hydrogenation with N-acylation... 

Palladium-carbon/sodium hydroxide Partial hydrogenation of N-heterocyclics... 

Phosphonium iodide/hydrogen iodide Partial hydrogenation of N>heterocycles... 

Ring hydrogenation of N-heterocycles with and without N-alkylation hy alcohols... 

Palladium-carbon hydrazine Selective hydrogenation of N-heterocycles (g)... 

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