Lewis Base-Promoted Ring-Opening 1,3-Dioxygenation of Unactivated Cyclopropanes Using a Hypervalent Iodine Reagent

A base-mediated aerobic oxidative synthesis of cyclopent-2-enol derivatives from doubly activated cyclopropanes and substituted acetonitriles

We report here that polysubstituted cyclopent-2-enols can be constructed by the one-pot reaction of doubly activated cyclopropanes and α-EWG substituted acetonitriles under mild basic conditions via a domino-ring-opening-cyclization/deacylation/oxidation sequence. Moreover, the synthetic applications of these cyclopent-2-enols have been demonstrated in the late-stage derivatization into functionalized cyclopentapyrimidin-4-ones and 2-hydroxy cyclopentanones with good yields.

Cooperative NHC/Photoredox Catalyzed Ring-Opening of Aryl Cyclopropanes to 1-Aroyloxylated-3-Acylated Alkanes

Cyclopropanes are an important class of building blocks in organic synthesis. Herein, a ring‐opening/arylcarboxylation/acylation cascade reaction for the 1,3‐difunctionalization of aryl cyclopropanes enabled by cooperative NHC and organophotoredox catalysis is reported. The cascade works on monosubstituted cyclopropanes that are in contrast to the heavily investigated donor–acceptor cyclopropanes more challenging to be difunctionalized. The key step is a radical/radical cross coupling of a benzylic radical generated in the photoredox catalysis cycle with a ketyl radical from the NHC catalysis cycle. The transformation features metal‐free reaction conditions and tolerates a diverse range of functionalities.

Ring Expansion Fluorination of Unactivated Cyclopropanes Mediated by a New Monofluoroiodane(III) Reagent

Herein, we report a new strategy for carbon-carbon bond scission and intramolecular ring expansion fluorination of unactivated cyclopropanes, which was accomplished with a new hypervalent fluoroiodane(III) reagent 1. This novel method delivers medicinally relevant 4-fully substituted fluoropiperidines in moderate to high yields with excellent regio- and diastereoselectivity. Reagent 1, which has an N-acetylbenziodazole framework, was readily synthesized via three steps in 76 % overall yield and was characterized by NMR spectroscopy and X-ray crystallography. Owing to the presence of a secondary I⋅⋅⋅O bonding interaction between the λ³ -iodane atom and the carbonyl oxygen of the acetyl group of the N-acetylbenziodazole framework, 1 has excellent stability and can be stored at ambient temperature for 6 months without any detectable decomposition. Density functional theory calculations and experimental studies showed that the reaction proceeds via a carbocation intermediate that readily combines with a fluoride ion to generate the product.