Annulations involving p-benzoquinones: stereoselective synthesis of fused, spiro and bridged molecules

Quinones are valuable structural motifs found in numerous natural products and pharmaceuticals. In particular, p-benzoquinones are of great interest because of their ready availability and versatile reactivity. They can serve as good Michael acceptors and participate in many cycloaddition, nucleophilic addition and multicomponent reactions. However, the construction of polycyclic architectures with increased stereochemical features is another perspective of quinone chemistry. The present review summarizes the recent advances (2018-2023) in stereoselective annulation involving p-benzoquinones for the construction of fused, spiro and bridged/cage frameworks. In this regard, different types of annulations, such as [3+2], [3+3], [3+2+1], [4+2] and [2+2], are discussed for accessing diverse fused heterocycles in a stereoselective manner. Some novel annulation methods are reviewed for building spiro heterocycles and cage molecules. Most of the reactions described in this review are simple, providing quick formation of the desired products with high stereoselectivity. In this regard, typical reaction mechanisms are presented to understand how quinoidal scaffolds show variable reactivity towards reaction partners.