This review summarizes the most recent progress made in C–H bond activation-initiated spiroannulation reactions and their applications in the construction of structurally diverse and biologically valuable spirocyclic scaffolds.
The advancements in the synthesis of nitrogen-containing heterocycles via Rh(III)-catalyzed chelation-assisted tandem C–H activation/carbene insertion/annulation with diazo compounds as carbene precursors have been summarized.
An unusual Au(I)/Sc(III)-co-catalyzed tandem spiroannulation/cycloisomerization of 3-(2-ethynylaryl)-N-tosylaziridine-2,2-diesters with indoles has been reported. A variety of 5H-benzo[b]carbazoles were obtained in moderate to good yields (30–88%).
A novel and practical approach to fluorene-based spirolactones has been described via BF3-promoted spiroannulation of α-keto acids and o-alkynyl biaryls. This metal-free cascade reaction provides a wide range of products in good to excellent yields.
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.