"A solution of 49.8 g (0.3 mole) of 3,4-dimethoxybenzaldehyde in 150 ml of 95% ethyl alcohol containing 20 ml of 29% aqueous ammonia (0.33 mole) and 25 g (0.3 mole) of ammonium acetate was hydrogenated at room temperature and 3 atm in the presence of 9.0 g of 5% rhodium on carbon. Uptake of hydrogen was complete in about 3 hr. After removal of catalyst, the filtrate and washings were concentrated and the residue distilled. A 64% yield of 3,4-dimethoxybenzylamine, bp 118-120 (1.5 mm), was obtained." Catalytic Hydrogenation in Organic Synthesis, Morris Freifelder, p. 92, 93, 1978.
I only mention this because this particular synth recognized the superiority of Rh/C over that of Pd/C, getting 64% with Rh/C and 55% with Pd/C. Unknown if this would be true for all ketone and aldehyde hydrogenations. I believe Pd/C of preferred due to fact that the addition of Rhodium on a carbon support is said to be dangerous. Also, most catalytic hydrogenations I've read involved extreme reaction environments, like several atmospheres of pressure. Any thoughts on different catalysts?
Yields I have read about for the reduction of non-aromatic nitro groups have been bad and, as it would seem, less favorable than aldehydes and ketones and taking longer periods of time. I believe that this might mean the use of Nitromethane would be a bad idea, allowing MDP2P to form stable products before nitromethane had even begun a conversion. My knowlegde here is very little, so not much emphasis should be placed on this assumption. However, NO2 groups were reduced to NH2 in all the catalytic hydrogenation reductions mentioned in pages 31-36 of the above mentioned reference.
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