title: Hydrogen-bond-assisted controlled C-H functionalization via adaptive recognition of a purine directing group.
abstract: 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.
authors.affiliation: Center for Catalytic Hydrocarbon Functionalizations, Institute of Basic Science (IBS), Daejeon 305-701, Republic of Korea.
authors.forename: Hyun Jin
authors.initials: HJ
authors.lastname: Kim
authors.forename: Manjaly J
authors.initials: MJ
authors.lastname: Ajitha
authors.forename: Yongjae
authors.initials: Y
authors.lastname: Lee
authors.forename: Jaeyune
authors.initials: J
authors.lastname: Ryu
authors.forename: Jin
authors.initials: J
authors.lastname: Kim
authors.forename: Yunho
authors.initials: Y
authors.lastname: Lee
authors.forename: Yousung
authors.initials: Y
authors.lastname: Jung
authors.forename: Sukbok
authors.initials: S
authors.lastname: Chang
mesh_terms: D000586:Amination; D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D011687:Purines / Q000737:chemistry*
chemical_list: D011687:Purines; D002244:Carbon; D006859:Hydrogen