Reduction by lithium in organic amines

When compared with the corresponding solutions in ammonia, solutions of lithium in amines appear as stronger but less selective reducing agents. 

Sometimes even isolated double bonds are attacked,57 58 wherefore cyclohexane derivatives usually appear as by-products on hydrogenation of aromatic compounds by this method. 

The reaction can be effected at low temperature or at the boiling point of the amine. Methylamine or a lower homolog, ethylenediamine,58 or an alkyl-aniline56 is usually used. They often act simultaneously as proton donors, but in other cases ammonium salts must be added after termination of the reaction. In reductions of abietic acid derivatives it was shown that reaction of lithium in ethylamine is milder than in presence of tert-pentyl alcohol.59 A review of these reactions is given by Birch and Smith.60 

It is rare today that reduction of ethylenic compounds by zinc and adds has advantages over catalytic hydrogenation however, it is still used for selective reduction of steroids,61 62 unsaturated diketones,62 64 and ethylenic derivatives containing sensitive functional groups.65 The normal method is to use zinc 

Karrer and C. H. Eugster, Helv. Chim. Acta, 32, 1934 (1949) R. Ramassent and A. Rassat, Bull. Soc. Chim. France, 1963, 2214. 

---