Quinones reactions with organometallics

Factors affecting whether quinones undergo addition or reduction hr their reactions with some organometallics, and with HN3, are discussed under Redox Reactions later. 

Reaction of organometallics such as alkyllithiums or Grignard reagents with p-quinones can give an addition product, or a hydroquinone (i.e. reduction product). The... 

Thus this system generates the reducing radical CHjOH so that when the solubility of a compound is higher in methanol than in water it is advantageous to effect its one-electron reduction by the radiolysis of its methanolic solution. This technique has been utilised, for example, for one-electron reduction of some organometallic complexes and quinones. As in water, e " can be converted to CHjOH via reactions (19) (with N2O) and (29) ... 

Lee et al. found that the DABCO-catalyzed MBH reaction between methyl acrylate and methyl vinyl ketone with 2,3-dihalo-1,4-naphthoquinone 60 forms a-vinylnaphthoquinones in moderate to good yields. The same authors subsequently reported additional examples of the use of DABCO attached enolate anion of methyl acrylate and MVK in substitution reactions of halo-quinones to form a-vinylquinone bonds, avoiding the use of organometallic reagents (Scheme 2.26). ... 

Another possible synthetic route to introduce ligands into an organometallic complex is the reaction of one of its low-valent species with radicals. Thus, an O- or N-centered radical is reduced to a monoanionic ligand while the metal center is oxidized. However, some apphcations of the radical-like properties of titanium(III) species are known in the literature. In that way, the free radical-like properties of CpTi Cb derivatives are observed in reactions, for example, with quinones [36] as well as with azo and diazo compounds [32], whereas the intermediately generated Cp2Ti Cl reagent is well introduced in organic reactions [37]. 

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