Potassium Graphite Intercalates as Reducing Agents

Graphite reacts with alkali metals - potassium, cesium and rubidium - to form lamellar compounds with different stoichiometries. The most widely known intercalate is the potassium-graphite which has the stoichiometry of CgK. In this intercalate the space between the graphite layers is occupied by K atoms. CgK functions as a reducing agent in various reactions such as reduction of double bonds in a,fl-unsaturated ketones [19], carboxylic acids and Schiff bases alkylation of nitriles [20], esters and imines [21] reductive cleavage of carbon-sulfur bonds in vinylic and allylic sulfones [22]. The detailed reaction mechanism of CgK is not known, and the special properties which are ascribed to the intercalate come either from the equilibrium between K+/K [23], or topochemical observations (the layer structure) [24]. 

Clocking and Kingston [25], and later Rabinovitz [26], showed that the reduction of phenyl halides (to obtain biphenyl) with CgK afforded 85-99% yield, in contrast 

The reduction of substituted naphthalene with CgK demonstrates the high selectivity of the reduction, as only the 1,4-dihydronaphthalene is obtained [29]. This method can be used as an alternative route to the Birch reduction and its 

CgK was also used in the reduction of PAHs, and the resulting anions were identical to those obtained by a direct reduction with a K mirror. The lower reactivity of CgK, however, makes it a more selective reagent [31]. 

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