Synthesis of Indazolo[2, 1-a]Cinnolines via Rhodium (III)-Catalyzed C–H activation/annulation under mild conditions. Issue 30 (26th July 2019)

• Record Type: Journal Article
• Authors: Hou, Wei; Xiong, Huan; Bai, Ruisong; Xiao, Zaozao; Su, Lin; Ruan, Bengfang Helen; Xu, Hongtao
• Is Part Of: Tetrahedron. Volume 75:Issue 30(2019)
• Page Start: 4005
• Page End: 4009
• Publication Date: 2019-07-26
• Subjects: Rhodium catalysis -- Strong directing group -- C–H/N–H functionalization -- Indazolo[2, 1-a]Cinnolines -- Fluorophores; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tet.2019.06.021
• Languages: English
• ISSNs: 0040-4020

Abstract

Abstract: A simple, robust and efficient Rh(III)-catalyzed synthesis of novel 12H-indazolo[2, 1- a ]cinnolin-12-ones has been developed via tandem C–H activation/annulation of 2-phenylindazolones with diazo compounds by using less developed secondary amine as an intrinsic directing group. Notably, a series of nondiscriminating conditions were obtained with excellent test yield. Also, this reaction is highly regioselective with broad substrate scope and both electron-donating and electron-withdrawing groups gave satisfactory yield under very mild conditions (room temperature to 40 °C). It is scalable, compatible with air and H2 O, and the only by-products are N2 and H2 O. Moreover, the synthesized products represent a new class of fluorophores and their initial spectroscopic characterization has been conducted. Graphical abstract: Image 1