Electrochemical C−C bond cleavage of cyclopropanes towards the synthesis of 1,3-difunctionalized molecules

Abstract

Electrochemistry has a lot of inherent advantages in organic synthesis and many redox reactions have been achieved under electrochemical condition. However, the electrochemical C−C bond cleavage and functionalization reactions are less studied. Here we develop electrochemical C−C bond cleavage and 1,3-difuntionalization of arylcyclopropanes under catalyst-free and external-oxidant-free conditions. 1,3-difluorination, 1,3-oxyfluorination and 1,3-dioxygenation of arylcyclopropanes are achieved with a high chemo- and regioselectivity by the strategic choice of nucleophiles. This protocol has good functional groups tolerance and can be scaled up. Mechanistic studies demonstrate that arylcyclopropane radical cation obtained from the anode oxidation and the subsequently generated benzyl carbonium are the key intermediates in this transformation. This development provides a scenario for constructing 1,3-difunctionalized molecules.

Electrochemical Ring-Opening Dicarboxylation of Strained Carbon–Carbon Single Bonds with CO2: Facile Synthesis of Diacids and Derivatization into Polyesters

“…Many examples of ring-opening difunctionalization of cyclopropanes/cyclobutanes have been reported in the presence of Lewis acids, transition metal catalysts, and/or oxidants . Very recently, electro- and/or photochemical radical-type ring-opening difunctionalization has attracted much attention because of the high efficiency and mild reaction conditions (Figure C). However, most examples have been reported with radical cations as the key intermediates under oxidative conditions.…”

Electrochemical Synthesis of 1,2,3-Thiadiazoles from α-Phenylhydrazones

“…To further prove the synthetic utility of our protocol, alicyclic/aliphatic group-containing adducts ( 3z and 3aa ) were also tested. In particular, the alicyclic moiety like the cyclopropyl preferred ring opening reactions under an electric current and generated open chain framworks; in spite of this under our protocol adduct 3z derived from cyclopropyl ketothioamide was successfully engaged in the generation of expected 1,2,3-thiadiazole product 4z in excellent yield [80% (Scheme a)]. Moreover, the adduct derived from n -butyl-substituted thioamide 3aa was also found to be suitable and generated the desired product 4aa in good yield [78% (Scheme b)].…”

Palladium-catalyzed stereoselective ring-opening reaction of aryl cyclopropyl ketones

“…Ring cleavage or enlargement may then occur under relatively mild conditions. 4 But so far, the reported ring-opening reactions of mono-activated cyclopropane derivatives require severe conditions assisted either by solid nucleophiles like the iodide anion, 5 or strong Lewis acids like TiCl 4 . 6,7 Moreover, substituted cyclopropanes can also undergo oxidative addition reactions with transition metals, usually forming metallacyclobutanes due to the cleavage of the more accessible distal C–C bond.…”