Recent Advancement in Palladium-Catalyzed C–C Bond Activation of Strained Ring Systems: Three- and Four-Membered Carbocycles as Prominent C3/C4 Building Blocks

Abstract

In recent years, transition metal-catalyzed strong C–C bond activation has significantly attracted the attention of synthetic chemists. This protocol enables simultaneous and direct functionalization of two different M–C bonds. Among different types of C–C bond activation strategies, strain-driven C–C bond activation has resulted in various otherwise difficult transformations. In this context, palladium catalyst has been extensively used and studied due to its robust reactivity and selectivity. Herein we have briefly discussed palladium-catalyzed C–C bond activation of three- and four-membered cycloalkane derivatives.

Palladium-Catalyzed Trans-Selective Synthesis of Spirocyclic Cyclobutanes Using α,α-Dialkylcrotyl- and Allylhydrazones

“…Additionally, the unwanted [3,3]-sigmatropic rearrangements of 1,5-dienyl starting materials must be avoided. , Lastly, there is considerable ring strain that develops during the C–C bond forming step, rendering 4- exo -trig cyclization endergonic (Figure B) . Indeed, the formation of cyclobutylcarbinyl Pd intermediates (CBC-Pd) is often used as a strategy for C–C bond cleavage, not C–C bond formation . Several reports using cationic Pd intermediates , have seen modest success but lack modularity, often requiring multistep syntheses for starting materials, and have not been extensively investigated for the synthesis of spirocycles.…”

Palladium-Catalyzed Skeletal Rearrangement of Cyclobutanones via C–H and C–C Bond Cleavage

“…Herein, we report on the development of a palladium-based system that catalyzes the skeletal rearrangement of cyclobutanones, in which neither an extra reactive functional group nor a directing group is needed. Therefore, unfunctionalized cyclobutanone derivatives can be directly converted into a wide variety of functionalized 1-indanones via C–C/C–H activation (Scheme c) …”

Palladium‐Catalyzed Fluorinative Bifunctionalization of Aziridines and Azetidines with gem‐Difluorocyclopropanes

“…(b) The ringopening of cyclic quaternary ammonium may be very difficult because of the weak nucleophilicity of the catalytic amount of fluoride. Herein, we present a palladiumcatalyzed fluorination and fluoroallylation of azardines with gem-difluorocyclopropanes [10][11] (Scheme 1c). This protocol provides a modular synthetic method to acquire β,β'bisfluorinated amines in atom economic manner.…”