Exploiting Strained Rings in Chelation Guided C−H Functionalization: Integration of C−H Activation with Ring Cleavage

Abstract

Strained ring systemsa re regarded as privileged coupling partnersi nd irected CÀHb ond functionalization and have emergeda sapotential research area in organic synthesis. The inherent ring strain in these systems acts as a driving force, allowing the facile construction of diversified structural scaffolds via integrating CÀHa ctivation and ringscission. The mechanistic underpinnings allows the implementation of ap lethora of CÀHb onds across plentiful or-ganic substrates, including the less reactive alkyl ones. Consideringt he synthetic space, this area will foster developments of novel synthetic methods in chelation guided CÀH functionalization. This review will focus on recent developments in transition-metal catalyzed chelation assisted concomitant CÀHa ctivation and ring scissiono fs trained rings to attain molecular complexity. Figure 1. Strained rings/carbocycles vs. heterocyclic counterparts.[a] Dr.

Iron-Catalyzed Ortho C–H Homoallylation of Aromatic Ketones with Methylenecyclopropanes

“…However, development of convenient methods for C–H homoallylation is still desired. We envisioned that methylene­cyclo­propanes (MCPs), which are prepared in two steps from alkenes, would be suitable coupling partners in the C–H homoallylation. The use of MCPs in arene homoallylation has only been reported for a Friedel–Crafts type method and has not been explored for reactions via C–H bond cleavage by transition metal catalysts.…”

Transition‐Metal‐Catalyzed Directing Group Assisted (Hetero)aryl C−H Functionalization: Construction of C−C/C‐Heteroatom Bonds

“…Since recent past, the directing group aided cleavage of strained rings have witnessed significant progress owing to their innate ring strain embodied within their cyclic frameworks. [67] In this vein, the directed CÀ H functionalization using aziridines as a viable coupling precursor has been achieved by the groups of Li [68] and Yoshikai [69] utilizing Rh and Co catalyzed conditions, respectively (Scheme 20). However, the metal-catalyzed ringscission of small ring systems within the vicinity of arene CÀ H bond in indole derivative remains a challenging task.…”

Recent Advances in Metal‐catalyzed Alkylation, Alkenylation and Alkynylation of Indole/indoline Benzenoid Nucleus

“…Three membered carbo‐ and heterocycles have been used as alkylating reagent. The reaction proceed via transition‐metal catalyzed ring‐scission of strained ring merging with C−H activation [6i,41] . In this regard, a proficient C7 allylation of indoline is accomplished with vinyl cyclopropanes via sequential C−H and C−C activation under rhodium(III)‐catalysis (Scheme 38).…”