Direct Functionalization of para-Quinones: A Historical Review and New Perspectives

Abstract

The direct functionalization of quinones has always fascinated research communities due to their biological and redox activities and subsequent application. Quinone motifs play a vital role as precursors for many bioactive compounds and materials; hence, many ingenious methodologies have been elaborated for exploring these units. A significant part of the synthetic strategies towards the functionalized quinones has been achieved by installing substituents on hydroquinones, phenols, or quinone itself by different oxidative coupling reactions via radical pathways with or without the utilization of metal catalysts. The functionalization of simple quinones via direct C−H bond remains challenging due to their inherited electronic nature and high bond dissociation energy. This review article summarizes the recent advancement made for functionalized quinones through direct functionalization of simple quinones. Our primary focus will be on the synthetic approaches and mechanistic pathways of these reactions that have appeared in the last two decades, along with a short historical importance of the quinone family.