Synthetic Applications of Sodium in Liquid Ammonia

Introduction

Sodium in liquid ammonia forms a useful reagent system for carrying out a variety of transformations. Sodium reacts slowly with ammonia to produce sodium amide and hydrogen (Figure 1). This reaction is catalyzed by metal ions such as iron, cobalt and nickel. The sodium/ammonia system forms an excellent reducing agent with a half-life potential of -2.59 V at -50 °C. [1]

Scheme 1

Besides its classical application in Birch reduction [2] it has been found to bring about several reactions such as the ­reductive cleavage of C-Cl, N-N, S-S and C-S bonds; nucleophilic substitution of the aryl halides, proton ­abstraction, reduction of alkenes and alkynes, aminolysis of trichlorosilanes, and multiple deprotections in a single step. These useful applications of this reagent system ­coupled with its ready availability make it a powerful tool for practical organic synthesis.

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