Nankai University chemists convert tetrasubstituted alkenes into fused δ-lactams with an Ir(III) catalyst
A group at Nankai University reported an Ir(III)-catalyzed nitrene-transfer cascade that turns congested tetrasubstituted alkenes into cycloalkane-fused δ-lactams under mild conditions.
Researchers at the State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University (Tianjin, China), have described a way to convert sterically congested tetrasubstituted alkenes into cycloalkane-fused δ-lactams. The work was published on 4 November 2026 in Nature Communications; the corresponding author is Hao Wang. nature.com
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Transition-metal-catalyzed nitrene transfer is an established strategy for alkene functionalization. According to the authors, its use on tetrasubstituted alkenes has remained severely underdeveloped.
Ir(III)-catalyzed cascade
The team reports an Ir(III)-catalyzed aziridination–rearrangement cascade triggered by a nitrene. It converts cyclic-substituted tetrasubstituted alkenes into cycloalkane-fused δ-lactams.
The reaction runs under mild conditions. The authors report excellent yields and uniformly high diastereoselectivities. nature.com
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The method is compatible with carbon-, oxygen- and nitrogen-based nucleophiles. According to the authors, the substrates include structurally complex and biologically relevant ones.
Mechanism: aziridination and aza-semipinacol rearrangement
Experimental and computational studies, the authors say, support the following sequence. An Ir–nitrenoid performs a concerted aziridination of the alkene and generates a strained tricyclic intermediate.
This intermediate then undergoes an aza-semipinacol rearrangement driven by strain release. The rearrangement gives a bicyclic azacarbocation. nature.com
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The azacarbocation can be intercepted by a nucleophile or can undergo elimination. These two routes lead to structurally diverse fused δ-lactam architectures, and the authors describe the access as rapid.
The authors present the result as a nitrene-triggered carbocationic rearrangement manifold for functionalizing tetrasubstituted alkenes. They state that it expands the synthetic potential of transition-metal-catalyzed nitrene transfer.
The study is a synthetic-chemistry method developed in the laboratory. The material does not describe applications of the products.
