Quinoid Carbene Mediated C(sp2)-Heteroatom Bond Formation

Abstract

C(sp2)-heteroatom bonds play a critical role in biologically active molecules, pharmaceuticals, and functional materials. Traditional methods for synthesizing these bonds often rely on transition metal-catalyzed cross-coupling reactions, such as the Buchwald-Hartwig and Ullmann reactions, which have limitations, including the requirement for elevated temperature and basic conditions. In recent years, diazo quinones have emerged as promising reagents for C(sp2)-heteroatom bond formation due to their unique structural and reactive properties, which include high electrophilicity and a tendency toward aromatization. This review highlights recent advances in the use of quinoid carbenes, derived from diazo quinones, for the construction of C(sp2)−N, C(sp2)−O, and C(sp2)−S bonds. Key methodologies discussed include rhodium-, iridium-, ruthenium- and palladium-catalyzed cross-coupling reactions, heteroatom-H bond insertion reactions, migration reactions and sigmatropic rearrangements. These methods offer mild, functional group-tolerant alternatives to traditional approaches, showcasing their utility in the synthesis of complex bioactive molecules, medicinally relevant compounds, and materials.