Reactions of methylenecyclopropanes and vinylidenecyclopropanes with N-fluorodibenzenesulfonimide

Divergent Fluorinations of Vinylcyclopropanes: Ring-Opening 1,5-Hydrofluorination and Ring-Retaining 1,2-Difluorination

Organofluorine compounds have been widely used in pharmaceutical, agrochemical, and material sciences. Reported herein are divergent fluorination reactions of vinylcyclopropanes with different electrophiles, which allow the facile synthesis of homoallylic monofluorides and vicinal-difluorides through ring-opening 1,5-hydrofluorination and ring-retaining 1,2-difluorination, respectively. Both protocols feature mild conditions, simple operations, good functional group tolerance, and generally good yields. The practicality of these reactions is demonstrated by their scalability, as well as the successful conversion of the formed homoallylic monofluorides into other complex fluorinated molecules.

Hypervalent iodine(iii)-mediated ring-expansive difluorination of alkynylcyclopropanes en route to the synthesis of difluorinated alkylidenecyclobutanes

Reported herein is a hypervalent iodine(iii)-mediated ring-expansive difluorination of alkynylcyclopropanes featuring a Wagner–Meerwein-type rearrangement to access a variety of difluorinated alkylidenecyclobutanes.

gem-Difluorination of Methylenecyclopropanes (MCPs) Featuring a Wagner-Meerwein Rearrangement: Synthesis of 2-Arylsubstituted gem-Difluorocyclobutanes

The geminal difluorocyclobutane core is a valuable structural element in medicinal chemistry. Strategies for gem-difluorocyclobutanes, especially the 2-substituted cases, are limiting and often suffer from harsh reaction conditions. Reported herein is a migratory gem-difluorination of aryl-substituted methylenecycloproanes (MCPs) for the synthesis of 2-arylsubstituted gem-difluorocyclobutanes. Commercially available Selectfluor (F-TEDA-BF₄) and Py·HF were used as the fluorine sources. The protocol proceeds via a Wagner-Meerwein rearrangement with mild reaction conditions, good functional group tolerance, and moderate to good yields. The product could be readily transformed to gem-difluorocyclobutane-containing carboxylic acid, amine, and alcohol, all of which are useful building blocks for biologically active molecule synthesis.

Catalyst-free geminal aminofluorination of ortho-sulfonamide-tethered alkylidenecyclopropanes via a Wagner-Meerwein rearrangement

A catalyst-free intramolecular geminal aminofluorination of ortho-sulfonamide-tethered alkylidenecyclopropanes has been developed. The reaction proceeded through two SET processes with Selectfluor to give a fluorinated cyclopropylcarbinyl cation and a further Wagner-Meerwein rearrangement to generate a cyclobutyl carbocation, which undergoes intramolecular nucleophilic capture by amide to forge fluorinated cyclobuta[b]indoline derivatives. A polycyclic multi-fluorinated byproduct was also formed through a Ritter-type reaction in some cases.

Gold(i)-catalyzed intramolecular hydroarylation and the subsequent ring enlargement of methylenecyclopropanes to cyclobutenes

Gold(i)-catalyzed intramolecular hydroarylation and the ring enlargement of methylenecyclopropanes containing aryl propargyl ether to give 2H-chromene derivatives and the corresponding cyclobutenes.