Reduction by solutions of alkali or alkaline-earth metals in liquid ammonia

Solutions of alkali metals in liquid ammonia constitute strongly nucleophilic reagents, but nevertheless their efficiency for reduction of unsaturated hydrocarbons barely surpasses that of the systems described above. 

Apart from exceptional cases,30 isolated double bonds and monocyclic aromatic systems are not attacked. Conjugated double bonds,4,31 however, aryl-substituted ethylenes,32 and polycyclic aromatic compounds4,33 can be partially hydrogenated with considerable success. Dimerization or further chain-formation of the starting material often occurs as a side reaction. 

An excess of sodium is usually used, at — 70° or — 33° (carbon dioxide bath or boiling point of ammonia). Ether, tetrahydrofuran, and benzene and its 

Levina, V. R. Skvarchenko, V. N. Kosstin, E. G. Treshchova, and A. S. Okune-vich, Sbornik Statei Obshch. Khim., Akad. Nauk SSSR, 1, 355 (1953) Chem. Abstr., 49, 829 (1955). 

9-Phenanthroic acid (5.69 g), sodium amide (1 g), and liquid ammonia (90 ml) are placed in a reaction vessel fitted with a reflux condenser that can be cooled to —70° by alcohol-Dry Ice and with a magnetic stirrer. The mixture is stirred until the sodium amide is wholly dissolved (ca. 4 h) and thereafter freshly cut, small pieces of sodium (1.2 g) are added during 1 h. The dark red mixture is stirred for a further 1.5 h and then slowly decolorized by ethanol (10 ml). The ammonia is then allowed to evaporate, the residue dissolved in water and acidified with hydrochloric acid, and the thick brown oil is extracted in ether (two 25-ml portions). The united extracts are washed with water, dried over anhydrous sodium sulfate, and treated with Norite. Evaporation of the ether yields the dihydro acid of m.p. 122-124°. 

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