Facile access to gem-difluorocyclopropanes via an N-heterocyclic carbene-catalyzed radical relay/cyclization strategy

Abstract

An N-heterocyclic carbene catalyzed difluorocyclopropanation of alkenes with aldehydes and CF2Br2 for facile and efficacious synthesis of a new class of functionalized gem-difluorocyclopropanes bearing acyl groups has been developed. The...

Radical Acylation of Alkenes by NHC‐Organocatalysis

“…However, one‐pot synthesis of 1,1‐dichlorocyclopropanes through NHC‐catalyzed trichloromethyl acylation and 3‐ exo ‐ tet cyclization could not be realized under the identical conditions because of the poor balance between the two processes mentioned above. Nevertheless, very recently, Du and co‐workers disclosed that one‐pot assembling of gem ‐difluorocyclopropanes via NHC‐catalyzed cascade radical‐relay/cyclization was achieved under very mild conditions using NHC‐2 as the catalyst (Scheme 12d) [23] …”

“…Nevertheless, very recently, Du and coworkers disclosed that one-pot assembling of gem-difluorocyclopropanes via NHC-catalyzed cascade radical-relay/cyclization was achieved under very mild conditions using NHC-2 as the catalyst (Scheme 12d). [23] Scheme 10. NHC-catalyzed difunctionalization of styrene via direct CÀ H activation of simple alkanes.…”

Radical-Polar Crossover Enabled Triple Cleavage of CF2Br2: A Multicomponent Tandem Cyclization to 3-Fluoropyrazoles

“…For example, Qing and co-workers realized a photoinduced selective bromodifluoromethylation of alkenes with CF 2 Br 2 under mild conditions. Very recently, the pioneering examples toward sequential debromation of CF 2 Br 2 have also been reported. − In 2022, the Studer group reported a novel strategy for accessing diverse five-membered rings bearing gem -difluoroalkenyl from substituted alkynes and CF 2 Br 2 via a photoinduced radical addition-translocation-cyclization, in which CF 2 Br 2 suffered from the single-electron reduction/radical β-bromo fragmentation process. Later on, Du and co-workers achieved the NHC-catalyzed difluoroolefination of 1,3-enynes by using CF 2 Br 2 as a C1F2 synthon, offering a fruitful way to a new class of functionalized gem -difluorovinyl allenes.…”

“…Later on, Du and co-workers achieved the NHC-catalyzed difluoroolefination of 1,3-enynes by using CF 2 Br 2 as a C1F2 synthon, offering a fruitful way to a new class of functionalized gem -difluorovinyl allenes. The same group also developed a sequential debromation of CF 2 Br 2 to access gem -difluorocyclopropanes with alkenes and aldehydes via a NHC-catalyzed radical relay process . However, the achievement of the precise triple bond cleavage of CF 2 Br 2 , used as a unique C1F1 synthon, has not been reported, although it may lead to the efficient formation of monofluorinated compounds.…”

“…The same group also developed a sequential debromation of CF 2 Br 2 to access gem-difluorocyclopropanes with alkenes and aldehydes via a NHC-catalyzed radical relay process. 7 However, the achievement of the precise triple bond cleavage of CF 2 Br 2 , used as a unique C1F1 synthon, has not been reported, although it may lead to the efficient formation of monofluorinated compounds. The synthetic challenges might be the high bond energy of the C−F bond and uncontrolled exhaustive defluorination.…”