The review highlighted diverse annulations, including nitrogen, oxygen, sulfur heterocycles and carbocylizations via Rh(iii)/Ir(iii)-catalyzed C–H functionalization/annulation with various arene and carbene precursors.
Herein, we report an acid-controlled highly tunable selectivity of Rh(III)-catalyzed [4 + 2] and [3 + 3] annulations of N-carboxamide indoles with iodonium ylides lead to form synthetically important tricyclic and tetracyclic N-heterocycles. Here, iodonium ylide serves as a carbene precursor. The protocol proceeds under operationally simple conditions and provides novel tricyclic and tetracyclic scaffolds such as 3,4-dihydroindolo[1,2-c]quinazoline-1,6(2H,5H)-dione and 1H-[1,3]oxazino [3,4-a]indol-1one derivatives with a broad range of functional group tolerance and moderate to excellent yields. Furthermore, the protocol synthetic utility was extended for various chemical transformations and was easily scaled up to a large-scale level.
The transition-metal-catalyzed C−H functionalization of sulfoxonium ylides with alkynes formally participates in [4 + 2] annulations to deliver the naphthol scaffolds. In contrast, herein we disclose the first Rh(III)-catalyzed C−H activation, followed by redox-neutral [3 + 2] annulation of sulfoxonium ylides with 1,3diynes, which delivers the alkynated indenone derivatives. This protocol features a good functional group tolerance, a broad substrate scope, moderate to excellent yields, and mild reaction conditions. The reaction mechanism was supported through ESI-HRMS by characterizing key intermediates in the catalytic cycle.
Metal carbenes play a pivotal role in transition‐metal‐catalyzed synthetic transfer reactions. The metal carbene is generated either from a diazo compound through facile extrusion of N2 with a metal catalyst or in situ generated from other sources like triazoles, pyriodotriazoles, sulfoxonium ylides and iodonium‐ylide. On the other hand, Co(III), Rh(III) & Ir(III)‐catalyzed C−H functionalizations have been well established as a key synthetic step to enable the construction of various synthetic transformations. Interestingly, in recent years, merging of these two concepts C−H activation and carbene migratory insertion gained much attention, in particular group 9 metal‐catalyzed arene C−H functionalizations with carbene precursors via carbene migratory insertion. In this review, we summarize recent advances in Co(III), Rh(III) & Ir(III)‐catalyzed direct C−H alkylation/alkenylation/arylation with carbene precursors and also discuss key synthetic intermediates within the catalytic cycles.
Described herein is the Rh(III)-catalyzed [3 + 2] annulations and C2-alkenylations of indoles with 1,3-diynes, which deliver the synthetically important 3H-pyrrolo[1,2-a]indol-3-ones and highly functionalized tetrasubstituted olefin derivatives. Importantly, in this methodology, the additive controlled selective formation of desired scaffolds. This synthetic strategy exhibits high efficiency and broad functional group compatibility. Furthermore, this protocol has been successfully extended to the synthesis of bisannulated and trisubstituted alkenes. The method is also smoothly applied for the synthesis of the core structure of protein kinase C inhibitor and melatonin analogues.
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