Hydrogenation of amides

Reduction of Carboxylic Acids to Alcohols. In addition to the nonsupported catalysts mentioned for the hydrogenation of amides to amines, mthenium and rhenium on alumina can be used to reduce carboxyHc acids to alcohols. The conditions for this reduction are somewhat more severe than for most other hydrogenation reactions and require higher temperatures, >150° C, and pressures, >5 MPa (725 psi) (55). Various solvents can be used including water. 

Hydrogenation of amides normally result in the formation of alcohols, whereas lactams give cyclic amines. The work presented in this paper is the first example that we are aware in which a lactam was hydrogenated by a ruthenium catalyst. To verify that acid promoted the lactam carbonyl hydrogenation, two... 

Reduction of CO and ketones Hydro formylation Fischer-Tropsch synthesis Synthesis of methanol from CO Hydrogenation of amides Alkyne cyclization Hydroxymethylation... 

Catalytic hydrogenation of amides to amines requires drastic conditions in general, a temperature of 250 to 265" and a pressure of 200 to 300 atm. over copper-chromium oxide catalyst using dioxane as the solvent. The yields of primary amines from unsubstituted amides are lowered mainly by the formation of secondary amines, viz.,... 

The homogeneous hydrogenation of amides having at least one aromatic ring on N by H2 is catalysed by complexes prepared in situ from [Ru(acac)3], 1,1,1-tris(diphenylphosphinomethyl)-ethane (triphos), and methane sulfonic acid in THF to give corresponding amines with selectivities as high as 93%. The system is also... 

Scheme 7 Hydrogenation of amides using various pincer catalysts...

Possible pathways for the hydrogenation of amides are shown in Scheme 6. A few cases of reductive cleavage of the C=0 bond with the formation of a secondary amine were reported [61-65]. 

Fig. 9 Selective hydrogenation of amides to the corresponding alcohols and amines catalysed by complex 6...

Many other functional groups are also reactive under conditions of catalytic hydrogenation. The reduction of nitro compounds to amines, for example, usually proceeds very rapidly. Ketones, aldehydes, and esters can all be reduced to alcohols, but in most cases these reactions are slower than alkene reductions. For most synthetic applications, the hydride transfer reagents to be discussed in Section 5.2 are used for reduction of carbonyl groups. Amides and nitriles can be reduced to amines. Hydrogenation of amides requires extreme conditions and is seldom used in synthesis, but reduction of nitriles is quite useful. Scheme 5.3 gives a summary of the approximate conditions for catalytic reduction of some common functional groups. 

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