Reductions and Oxidations with Metals

Reductions for which group 1 metals are used in organic chemistry can be divided into two broad classes those that involve addition of H2 across a 77 bond, such as conjugate reduction and the Birch reduction, and those in which a bonds between non-H atoms are formed or broken, such as the reduction of C-X bonds and acyloin and pinacol condensations. 

Reductions involving addition of H2 across a 77 bond follow one or both of the following two sequences of events. 

An electron is transferred from the metal to the substrate to give a radical anion. 

A second electron transfer to the radical anion occurs to give a closed-shell dianion. 

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The major classes of nonchain free-radical reactions are photochemical reactions, reductions and oxidations with metals, and cycloaromatizations. 

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