Lithium metal reduction fullerenes

The lithium metal reduction of 7r-conjugated hydrocarbons and fullerenes... 

In the meantime, it was found that addition of corannulene, which serves as an efficient electron shuttle between the lithium metal and the solid fullerenes, facilitates the reduction of the fullerenes to their hexaanions (Figure 19). This finding was very crucial for the continuing study of charged fullerenes40b. 

In addition to being more selective, dissolved calcium metal functions in a similar way to lithium and sodium metals towards organic functional groups [45]. Tab. 4.2 lists reductions giving the same products by the three dissolved metals. Among these, calcium affords the highest yields for some substrates (entries 1-3). The compounds in Tab. 4.2 include an aldehyde, indole [46], aryl ketone, enone, naphthalene [47], pyridine N-oxide [48], benzyl alcohol, styrene, and buckminster-fullerene. 

The Birch reduction with alkali metals in liquid ammonia has been described for Cso already in 1990, just shortly after its isolation. A mixture of highly hydrogenated fullerene compounds QqHj, (18 < x < 36) is generated especially with lithium in ammonia in the presence of tert-butanol. Again C >Hi8 and CgoHsg are the major products. Derivatives with even more hydrogen attached carmot be obtained by Birch reduction as they decompose at the conditions applied. 

In this chapter we concentrate on reduction processes of carbon-rich systems. The formation of anions and radical anions of -conjugated monocyclic systems, cyclophanes, bowls and fullerenes is described. Carbon-rich compounds can be reduced directly by contact with alkali metals Li, Na, K, Rb and Cs, which have a low reduction potential. Proton, carbon and lithium NMR and EPR spectroscopies are the main methods used to gain a better understanding of the mono- and polycyclic systems in solution. Special attention will be given to modes of electron delocalization, aromaticity, anti-aromaticity, as well as aggregation, bond formation and bond cleavage processes of diamagnetic electron transfer products. Electrochemical reductions will be briefly discussed. 

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