title: Rhodium(III)-catalyzed N-nitroso-directed C-H addition to ethyl 2-oxoacetate for cycloaddition/fragmentation synthesis of indazoles.
abstract: Rh(III) -catalyzed N-nitroso-directed CH addition to ethyl 2-oxoacetate allows subsequent construction of indazoles, a privileged heterocycle scaffold in synthetic chemistry, through the exploitation of reactivity between the directing group and installed group. The formal [2+2] cycloaddition/fragmentation reaction pathway identified herein, a unique reactivity pattern hitherto elusive for the N-nitroso group, emphasizes the importance of forward reactivity analysis in the development of useful CH functionalization-based synthetic tools. The synthetic utility of the protocol is demonstrated with the synthesis of a tricyclic-fused ring system. The diversity of covalent linkages available for the nitroso group should enable the extension of the genre of reactivity reported herein to the synthesis of other types of heterocycles.
authors.affiliation: Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093 (P. R. China).
authors.forename: Jinsen
authors.initials: J
authors.lastname: Chen
authors.forename: Pei
authors.initials: P
authors.lastname: Chen
authors.forename: Chao
authors.initials: C
authors.lastname: Song
authors.forename: Jin
authors.initials: J
authors.lastname: Zhu
keywords: CH functionalization; cycloaddition/fragmentation; directing groups; installed groups; rhodium