Benzoquinones, possessing two α,β-unsaturated carbonyl groups in a six-carbon atom ring, represent a uniquely important synthetic unit. Their centrality in the preparation of such important commercial substances as dyes and pharmaceuticals has resulted in extensive study of a variety of synthons. In living matter benzoquinones are ubiquitous and vital to human metabolism. Quinones are of special interest to biochemists and to both synthetic and theoretical organic chemists. The types of reactions most often reported are: nucleophilic addition, photochemical, cycloaddition, electrophilic addition, radical alkylation, electrochemical, oxidation, and nucleophilic substitution. The synthesis of quinones is usually accomplished through oxidation of phenols or anilines. A wide variety of oxidants has been used, but quinones of higher oxidation potential are often the reagent of choice. Quinones of low molecular weight should be treated with care in their storage and handling. The literature reviewed is through August, 2005.

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