title: Regioselective introduction of heteroatoms at the C-8 position of quinoline N-oxides: remote C-H activation using N-oxide as a stepping stone.
abstract: Reported herein is the metal-catalyzed regioselective C-H functionalization of quinoline N-oxides at the 8-position: direct iodination and amidation were developed using rhodium and iridium catalytic systems, respectively. Mechanistic study of the amidation revealed that the unique regioselectivity is achieved through the smooth formation of N-oxide-chelated iridacycle and that an acid additive plays a key role in the rate-determining protodemetalation step. While this approach of remote C-H activation using N-oxide as a directing group could readily be applied to a wide range of heterocyclic substrates under mild conditions with high functional group tolerance, an efficient synthesis of zinquin ester (a fluorescent zinc indicator) was demonstrated.
authors.affiliation: Department of Chemistry, Korea Advanced Institute of Science & Technology (KAIST) , Daejeon 305-701, Korea.
authors.forename: Heejun
authors.initials: H
authors.lastname: Hwang
authors.forename: Jinwoo
authors.initials: J
authors.lastname: Kim
authors.forename: Jisu
authors.initials: J
authors.lastname: Jeong
authors.forename: Sukbok
authors.initials: S
authors.lastname: Chang
mesh_terms: D000577:Amides / Q000737:chemistry; D002384:Catalysis; D054879:Halogenation; D007495:Iridium / Q000737:chemistry; D008958:Models, Molecular; D010087:Oxides / Q000737:chemistry*; D011804:Quinolines / Q000737:chemistry*; D012238:Rhodium / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000577:Amides; D010087:Oxides; D011804:Quinolines; D007495:Iridium; D012238:Rhodium; C037219:quinoline