Fundamental and applied aspects of the chemistry of acetylenylquinones

Abstract

In addition to the reported synthetic routes for the acetylene derivatives of quinones, a detailed analysis of the fundamental chemical, physicochemical, and biological properties of this class of compounds is presented herein. The advantages of Pd- and Cucatalyzed cross-coupling of terminal alkynes with iodarenes via the Sonogashira reaction to produce new acetylenylquinones with predetermined properties are examined. Here, combining quinoid and acetylene residues into one molecule gives the resulting compounds chemical specificity, as demonstrated by several reported examples of non-trivial transformations. In particular, the presence of the quinoid cycle significantly increases the electrophilicity of the triple bond and determines the range of transformation possibilities. Moreover, acetylenylquinones have heightened sensitivity to both external (such as the reaction temperature and the nature of the solvent) and internal (e.g., the structure of substituents in the nucleus and the acetylene fragment) factors. For example, regioselective cleavage of a strong triple bond under the action of amines is possible in the absence of a metal catalyst. Peri-substituted acetylenyl-9,10-anthraquinones are most suited for the synthetic route because of the proximity of the acetylene and carbonyl groups. Mechanisms of reactions of selective alkynylquinones are described.