Unsaturated nitriles, hydrogenation selective

The selectivity of RNH2 on M/A1203 and Raney catalysts decreased in the order Co Ni Ru>Rh>Pd>Pt. This order corresponds to the opposite sequence of reducibility of metal-oxides [8] and standard reduction potentials of metalions [9], The difference between Group VIII metals in selectivity to amines can probably been explained by the difference in the electronic properties of d-bands of metals [3], It is interacting to note that the formation of secondary amine, i.e. the nucleophilic addition of primary amine on the intermediate imine can also take place on the Group VIII metal itself. Therefore, the properties of the metal d-band could affect the reactivity of the imine and its interaction with the amine. One could expect that an electron enrichment of the metal d-band will decrease the electron donation from the unsaturated -C=NH system, and the nucleophilic attack at the C atom by the amine [3], Correlation between selectivity of metals in nitrile hydrogenation and their electronic properties will be published elsewhere. 

Unsaturated nitriles are converted smoothly to the saturated compounds by selective hydrogenation over palladinized charcoal or by chemical reduction. " The reaction is of special value in the preparation of a variety of substituted cyano compounds from the olefinic nitriles obtained in cyanoacetic ester condensations (method 387). 

Cationic Rh complexes [RhL(C0)(PPh3)2]C104 (L = unsaturated nitrile) show catalytic activities for the hydrogenation of a,3-unsaturated nitriles under mild conditions (30 °C). Selective reduction of the carbon-carbon double bonds of a,3-unsaturated carbonyls also occurs in high yield with [ Rh( 1,5-hexa-diene)Cl 2] and a phase transfer catalyst in aqueous media. ... 

Selective reduction of the olefin unit of the a,p-unsaturated nitrile is accomplished essentially with two systems one by catalytic hydrogenation using Pd/C, the other using magnesium in MeOH, a reagent combination known for its ability to reduce a,P-unsaturated nitriles. 

All of the stereoisomerie methyl 2,3-anhvdro-6-deoxy-DL-hexo-pyranosides have been prepared by epoxidation of 2,3-unsaturated pyranosides (328-331, R = Me) with hydrogen peroxide-benzo-nitrile. The H-n.m.r. data of their 4-O-acetyl derivatives were reported, and discussed in connection with configurational and conformational assignments.223 The1 regio- and stereo-selectivity of the... 

---