Cobalt-Catalyzed C–H Cyanation of (Hetero)arenes and 6-Arylpurines with <i>N</i>-Cyanosuccinimide as a New Cyanating Agent
作者:Amit B. Pawar、Sukbok Chang
DOI:10.1021/ol503680d
日期:2015.2.6
A cobalt-catalyzed C–H cyanation reaction of arenes has been developed using N-cyanosuccinimide as a new electrophilic cyanating agent. The reaction proceeds with high selectivity to afford monocyanated products with excellent functional group tolerance. Substrate scope was found to be broad enough to include a wide range of heterocycles including 6-arylpurines.
A cationic cobalt(III)‐catalyzeddirectCH 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
Cobalt(III)-Catalyzed C–H Amidation of Arenes using Acetoxycarbamates as Convenient Amino Sources under Mild Conditions
作者:Pitambar Patel、Sukbok Chang
DOI:10.1021/cs501860b
日期:2015.2.6
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.
Hydrogen-Bond-Assisted Controlled C–H Functionalization via Adaptive Recognition of a Purine Directing Group
作者:Hyun Jin Kim、Manjaly J. Ajitha、Yongjae Lee、Jaeyune Ryu、Jin Kim、Yunho Lee、Yousung Jung、Sukbok Chang
DOI:10.1021/ja4118472
日期:2014.1.22
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 repulsion between the first installed ArNH and the directing group.