Transition-Metal-Free Synthesis of Fused Quinazolinones by Oxidative Cyclization of N-Pyridylindoles

Abstract

An unprecedented synthesis of fused quinazolinones from N-pyridylindoles under oxidative conditions using a combination of (diacetoxyiodo)­benzene and K2S2O8 is reported. The reaction is metal-free, has a broad substrate scope, is operationally simple with short reaction time, and provides 11H-pyrido­[2,1-b]­quinazolin-11-one derivatives in moderate to high yields. It is believed to proceed via an in situ generated 2-hydroxy-1-(pyridin-2-yl)­indolin-3-one as the key reaction intermediate, which undergoes a C–C bond cleavage to produce an electrophilic C-3 site in N-pyridyl indole. Subsequent nucleophilic attack by pyridyl nitrogen results in its cyclization.

Aggregation and Solvation of Sodium Hexamethyldisilazide: Across the Solvent Spectrum

“…Pyridine is shown both spectroscopically and computationally to be moderately superior to THF as a ligand for LiHMDS and other lithium salts . It may find niche applications in the chemistry of NaHMDS, but a potentially greater motivation would be to understand pyridine–sodium interactions in putative S N Ar reactions and other organosodium reactions of pyridine-based heterocycles . Both titrations and computations suggest the dimer is disolvated.…”

Metal‐Free Synthesis of Anthranils by PhIO Mediated Heterocyclization of ortho‐Carbonyl Anilines

“…Most of these methods suffer from use of strong acid/base, transition metal, high temperature, pre‐functionalized substrates and generate toxic by‐products such as tin. In continuation of our research on PhIO mediated heterocycle synthesis [11a–b] …”

Pd and photoredox dual catalysis assisted decarboxylative ortho-benzoylation of N-phenyl-7-azaindoles

“…Furthermore, an ortho -selective benzoylation of these molecules under thermal conditions has not been reported. In view of our ongoing interest in transition metal mediated C–C, 8 C–N 9 and C–S 10 bond formation and photoredox assisted C–H bond functionalization 11 in diverse heterocycles, we delved into exploring the ortho -benzoylation of N -phenyl-7-azaindoles (Scheme 1b). To the best of our knowledge, the compatibility of N -phenyl-7-azaindoles for synthetic modifications in visible light is still unexplored.…”