Hypervalent iodine promoted the synthesis of cycloheptatrienes and cyclopropanes

Copper-catalyzed alkyne oxidation/Büchner-type ring-expansion to access benzo[6,7]azepino[2,3-b]quinolines and pyridine-based diones

General access to highly valuable seven-membered rings via Büchner-type reaction remains a formidable challenge. Here we report a Cu-catalyzed intermolecular oxidation of alkynes using N-oxides as oxidants, which enables expedient preparation of valuable benzo[6,7]azepino[2,3-b]quinolines and pyridine-based diones. Importantly, in contrast to the well-established gold-catalyzed intermolecular alkyne oxidation, the dissociated pyridine or quinoline partner could be further utilized to construct N-heterocycles in this system and the reaction most likely proceeds by a Büchner-type ring expansion pathway. A mechanistic rationale for this cascade cyclization is supported by DFT calculations.

Electrochemically Promoted [3 + 2] Annulation of Imidazo[1,2-a]pyridine with Alkynes

The efficient electrochemically promoted [3 + 2] annulation of imidazo[1,2-a]pyridines with alkynes using traceless electrons as green reagents has been developed, leading to the synthesis of a large class of polycyclic heteroaromatics in good yields with a broad substrate scope under mild and green conditions. The scaled-up experiment, follow-up procedures, and potential biological applications show the practicability and feasibility of the electrochemical method.

Recent Updates on Electrogenerated Hypervalent Iodine Derivatives and Their Applications as Mediators in Organic Electrosynthesis

With the renaissance of chemical electrosynthesis in the last decade, the electrochemistry of hypervalent iodine compounds has picked up the pace and achieved significant improvements. By employing traceless electrons instead of stoichiometric oxidants as the alternative clean “reagents”, many hypervalent iodine compounds were efficiently electro-synthesized via anodic oxidation methods and utilized as powerful redox mediators triggering valuable oxidative coupling reactions in a more sustainable way. This minireview gives an up-to-date overview of the recent advances during the past 3 years, encompassing enhanced electrosynthesis technologies, novel synthetic applications, and ideas for improving reaction sustainability.

Electrochemically-promoted synthesis of benzo[b]thiophene-1,1-dioxides via strained quaternary spirocyclization

We report an approach for the synthesis of benzothiophene motifs under electrochemical conditions by the reaction of sulfonhydrazides with internal alkynes. Upon the formation of a quaternary spirocyclization intermediate by the selective ipso-addition instead of an ortho-attack, the S-migration process was rationalized to lead to the products. Computational studies revealed the selectivity and the compatibility of drug molecules showcased the potential application of the protocols.

We report an approach for the synthesis of benzothiophene motifs under electrochemical conditions by the reaction of sulfonhydrazides with internal alkynes.