A Hypervalent Iodine-Mediated Convenient Synthesis Of Indoloquinolinones

Indoloquinolinone is an important core structure, which can be found in many natural alkaloids and pharmaceutical agents that possess important biological properties. Literature survey shows a handful of strategies have been developed for the construction of the indoloquinolinone skeleton. Although all these strategies have their respective merits in the construction of the biologically important indoloquinolinone skeleton, we believe developing more convenient and more economic methods is still in demand.A series of substituted indoloquinolinones were readily synthesized, via two steps, from indole-2-carboxylic acid and its derivatives: a 3-arylation of indole-2-carboxamides and a subsequent PIDA-mediated oxidative C-N bond formation. The underpinning strategy involves a Cu(I)-promoted C(sp2)-C(sp2) coupling and an iodosobenzene diacetate(PIDA)-mediated oxidative C(sp2)-N coupling.We have synthesized the 3,N-diarylated compound to verify regioselective of the iodosobenzene diacetate(PIDA)-mediated C-N bond formation step. The experiment result shows that the cyclization occurred between N atom and the phenyl ring at C3 position rather than the phenyl ring on the N atom of indole under oxidative conditions.Both the N-methoxy and N-benzyl group in the final product could be conveniently removed by NaH/DMF, by adopting the known methods, to afford the NH-free indoloquinolinone products. All the compounds have been well characterized by 1H NMR, 13 C NMR.