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.
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.
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.
A Co(III)-catalyzed C–H functionalization/spiroannulation of 1,3-indandione with alkenes has been developed for the synthesis of spiroindenes. This efficient protocol features excellent functional group tolerance and high atom- and step-economy.
A [3 + 2]-spiroannulation of 2-aryl-1,4-benzoxazines with 4-hydroxy-2-alkynoates has been developed for the synthesis of highly rigid spirolactones through a cascade of ortho-C–H annulation followed by lactonization.