One-pot C-N/C-C bond formation and oxidation of donor-acceptor cyclopropanes with tetrahydroisoquinolines: access to benzo-fused indolizines.

One-pot C-N/C-C bond formation of donor-acceptor cyclopropanes (DACs) with tetrahydroisoquinolines (THIQs) has been achieved to furnish benzo-fused indolizines. These reactions involve a MgI2-catalyzed ring opening of DACs and oxidative annulation using Mn(OAc)3·2H2O. The substrate scope and functional group diversity are the important practical features.

Expedient C-H allylation of sulfoxonium ylides: merging C-H and C-C/C-het bond activation.

Sulfoxonium ylide chelation-assisted C-H allylation of arenes has been accomplished utilizing strained vinyl carbo/heterocycles as the allyl surrogates via sequential C-H and C-C/het bond activation. Broad substrate scope, Co-catalysis, selectivity, and late-stage drug mutation are the important practical features.

Palladium-Catalyzed Annulative Coupling of Spirovinylcyclopropyl Oxindoles with p-Quinone Methides.

Pd-catalyzed annulative coupling of spirovinylcyclopropyl oxindoles with p-quinone methides has been accomplished via cascade carbon-carbon bond formation to afford bis-spirooxindole scaffolds. The mild reaction conditions, diastereoselectivity, functional group diversity, post-synthetic transformations, and mechanistic studies using DFT calculations are the important practical features.

Expedient (3+3)-annulation of in situ generated azaoxyallyl cations with diaziridines.

Efficient annulation of in situ formed azaoxyallyl cations using a base has been accomplished with diaziridines to provide 1,2,4-triazines at room temperature. The substrate scope, scale up, functional group tolerance and transition-metal free reaction conditions are the important practical features.

Cascade C-H Activation/Annulation of Sulfoxonium Ylides with Vinyl Cyclopropanes: Access to Cyclopropane-Fused α-Tetralones.

Rh-catalyzed weak and traceless directing-group-assisted cascade C-H activation and annulation of sulfoxonium ylides with vinyl cyclopropanes as a coupling partner have been accomplished to furnish functionalized cyclopropane-fused tetralones at moderate temperature. The C-C bond formation, cyclopropanation, functional group tolerance, late-stage diversifications of drug molecules, and scale-up are the important practical features.

Expedient Ni(OTf)2/visible light photoredox-catalyzed annulation of donor-acceptor cyclopropanes with cyclic secondary amines.

The annulative coupling of donor-acceptor cyclopropanes with cyclic secondary amines is reported using the combination of Ni(OTf)2 and visible light assisted eosin Y catalysis for tandem C-N and C-C bond formation. The reaction sequence provides a potential synthetic tool for the construction of pyrrolotetrahydroisoquinolines.

The transition-metal-catalyzed stereoselective ring-expansion of vinylaziridines and vinyloxiranes.

The transition-metal-aided stereoselective construction of sp3-carbon-rich heterocyclic scaffolds using strained-ring systems has received considerable attention in recent years due to the prominent presence of these scaffolds in myriad natural products, bioactive molecules, and pharmaceutical components. In this area, the catalytic ring-enlargement of vinylaziridines and vinyloxiranes plays a predominant role when synthesizing high sp3-content biorelevant heterocyclic compounds. This article aims to portray recent advancements in the ring-expansion of vinylaziridines and vinyloxiranes for accessing densely functionalized stereoselective heterocycles that have been developed over the past five years, with an emphasis on the substrate scopes and mechanistic insights into the key methodologies, and it is arranged based on the transition metals used and the ring sizes of the heterocyclic scaffolds.