The linear or branched allyl moieties on aromatic rings are well-known as ubiquitous structural motifs found in a range of natural products and medicinally relevant molecules. They also represent an important class of organic intermediates for the transformation of an olefin group into many useful functional groups. Established methods for the installation of allylic groups rely primarily on nucleophilic substitution or transmetalation of aryl metal complexes to allyl electrophiles, Lewis acid-mediated Friedel–Crafts allylation of electron-rich arenes, and Tsuji–Trost allylation reactions with π-allyl species. Complementing previous protocols, the transition metal-catalyzed allylation reactions via C–H activation strategy using various allylic surrogates like allylic acetates, allylic carbonates, allylic phosphonates, allylic halides, allylic alcohols, vinyl oxiranes, allenes, 1,3-dienes, and others have recently emerged as a powerful tool for creating the corresponding allyl, crotyl and prenyl moieties. ...

Recent Advances in Catalytic C(sp2)–H Allylation Reactions

The Co(III)-catalyzed direct C–H amidation of arenes has been developed using O-acylcarbamates as a convenient amino source. This reaction proceeded in high efficiency under external oxidant-free conditions with a broad range of arene substrates, including 6-arylpurines bearing sensitive functional groups, thus furnishing synthetically versatile arene N-carbamate products.

Cobalt(III)-Catalyzed C–H Amidation of Arenes using Acetoxycarbamates as Convenient Amino Sources under Mild Conditions

A cationic cobalt(III)-catalyzed direct C-H amidation of unactivated (hetero)arenes and alkenes by using 1,4,2-dioxazol-5-ones as the amidating reagent has been developed. This transformation proceeds efficiently under external oxidant-free conditions with a broad substrate scope. Moreover, 6-arylpurine compounds, which often exhibit high potency in antimycobacterial, cytostatic, and anti-HCV activities, can be smoothly amidated, thus offering a mild protocol for their late stage functionalization.

Cationic Cobalt(III)‐Catalyzed Aryl and Alkenyl C ? H Amidation: A Mild Protocol for the Modification of Purine Derivatives

We have developed the Rh-catalyzed selective C–H functionalization of 6-arylpurines, in which the purine moiety directs the C–H bond activation of the aryl pendant. While the first C–H amination proceeds via the N1-chelation assistance, the subsequent second C–H bond activation takes advantage of an intramolecular hydrogen-bonding interaction between the initially formed amino group and one nitrogen atom, either N1 or N7, of the purinyl part. Isolation of a rhodacycle intermediate and the substrate variation studies suggest that N1 is the main active site for the C–H functionalization of both the first and second amination in 6-arylpurines, while N7 plays an essential role in controlling the degree of functionalization serving as an intramolecular hydrogen-bonding site in the second amination process. This pseudo-Curtin–Hammett situation was supported by density functional calculations, which suggest that the intramolecular hydrogen-bonding capability helps second amination by reducing the steric repulsio...

Hydrogen-bond-assisted controlled C-H functionalization via adaptive recognition of a purine directing group.

Cp*CoIII-Catalyzed Dehydrative C–H Allylation of 6-Arylpurines and Aromatic Amides Using Allyl Alcohols in Fluorinated Alcohols

Synthesis of fused N-heterocycles via tandem C–H activation

Palladium-catalyzed C–H bond functionalization of C6-arylpurines

The synthesis of fused N-heterocycles is developed using an intramolecular cyclization of purines or benzimidazoles.

Synthesis of Fused N‐Heterocycles via Tandem C—H Activation.

C6-Modified purines can be obtained under Pd catalysis with purine serving as a directing group for the ortho C—H activation of the respective aryl group.

Ge Meng

Papers

Synthesis of fused N-heterocycles via tandem C–H activation

Palladium-catalyzed C–H bond functionalization of C6-arylpurines

Synthesis of Fused N‐Heterocycles via Tandem C—H Activation.

Palladium‐Catalyzed C—H Bond Functionalization of C6‐Arylpurines.