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Dearomatizing spirocyclization reactions are very appealing synthetic strategies to generate functionalized three-dimensional scaffolds from simple two-dimensional precursors. Recently, the field of transition-metal-catalyzed dearomatizing spirocyclization reactions of indolyl ynones has burgeoned, as the construction of synthetically challenging quaternary spirocyclic carbons is easily achieved. In this review, we introduce an overview of advances in the transition-metal-catalyzed dearomatizing spirocyclization reactions of indolyl ynones, with the reactions being categorized according to type of catalyst.

An efficient copper-catalyzed oxidative cyclization of diynes is described. A range of functionalized γ-lactams can be readily constructed by using this protocol. This copper-catalyzed oxidative process proceeds through an alkyne oxidation, carbene/alkyne metathesis, and donor–donor carbene oxidation sequence. The use of readily available substrates, high flexibility, a simple procedure, and mild reaction conditions render the procedure a viable alternative for the preparation of functionalized γ-lactams.

Described herein is a copper-catalyzed multifunctionalization of indolyl ynones, allowing the synthesis of dihalogen-substituted spiroindoles. This Cu catalysis is also applicable to the synthesis of cyclopenta[c]quinolin-3-ones via decarbonylation.

This review will focus on gold-catalyzed cycloadditions of allenes as efficient methods of assembling functionalized cyclic moleculesviagold carbenes.

Catalyst-dependent oxidative cyclization of diynes with pyridine N-oxides is achieved using an amide directing group. Non-polarized and aminated alkyne could be selectively activated by copper and gold, thus leading to divergent synthesis of a range of pyrroles and dihydroindeno[1,2-c]pyrrol-3(2H)-ones. It should be noted that this difference might be attributed to the multicoordinated Cu center and the linearly aligned dicoordinated Au center.

In recent years, transition-metal-catalyzed tandem cyclization reactions of alkynes, especially those involving a metal carbene intermediate, have received worthwhile interest, as this type of reaction does not require the use of risky and potentially explosive diazo compounds as starting materials for carbene generation. A significant and general strategy for the stereospecific synthesis of 5-membered cycles is Nazarov cyclization based on the 4π-conrotatory electrocyclization of a conjugated pentadienyl cation to afford a cyclopentenyl cation. In this review, we introduce an overview of recent advances in the transition-metal-catalyzed Nazarov cyclization of alkynes via a metal carbene intermediate, and categorize these reactions according to the structure of the metal carbene. Our aim is to accelerate advancements in this enchanting area of research.