Pd-Catalyzed Ring Restructuring of Oxazolidines with Alkenes Leading to Fused Polycyclic Indolizines

Synthesis of Tetrasubstituted Pyrroles via DBU-Mediated Cyclization of Unactivated Propargyl Tertiary Amines

Compared with the well-developed cyclization of functionalized propargylamines, the use of unactivated tertiary propargylamines to access pyrroles remains challenging. Herein, we report an efficient method for constructing tetrasubstituted pyrroles via a DBU-mediated intramolecular cycloaddition of N-alkyl propargylamines. This reaction employs cyclization to access dihydropyrrole intermediates, followed by oxidation to produce pyrroles in the presence of 2,3-dichloro-5,6-dicyano-p-benzoquinone. In addition, a broad substrate scope, high atom economy, high selectivity, and simple operation are also advantages of this protocol.

Organocatalytic Deoxygenative [3+2] Cycloaddition of N-Hydroxyamides with Alkynes to Access Isoxazoles

Although the transition-metal-catalyzed [3+2] cycloadditions to access isoxazoles have been described well, organocatalytic methods remain underdeveloped. Herein, we report the use of an organophosphine catalyst for the preparation of a series of isoxazoles with exceptional regioselectivity via the [3+2] cycloaddition of N-hydroxyamides and alkynes. The scope of this organocatalytic transformation is broad, tolerating numerous functional groups and proceeding uniformly in an environmentally friendly, simple, and efficient manner.

Skeletal Editing of Isatins for Heterocycle Molecular Diversity

Isatins have been widely used in the preparation of a variety of heterocyclic compounds, where the skeletal editing of isatins has shown significant advantages for the construction of diverse heterocycles. This review highlights the progress made in the last decade (2013-2023) in the skeletal editing of the isatin scaffold. A series of ring expansion reactions for the construction of quinoline skeleton, quinolone skeleton, polycyclic quinazoline skeleton, medium-sized ring skeleton, as well as a series of ring opening reactions for the generation of 2-(azoly)aniline skeleton by the cleavage of C-C bond and C-N bond are highlighted. It is hoped that this review will provide some understanding of the chemical transformations of isatins and contribute to the further realization of its molecular diversity.

Synthesis of N-alkenylisoquinolinones via palladium-catalyzed cyclization/C4–O bond cleavage of oxazolidines

A palladium-catalyzed cascade ring-opening reaction to synthesize N-alkenylisoquinolinones via cyclization and C–O bond cleavage is reported.