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.
Here, we report a metal‐free synthesis of anthranils from ortho‐carbonyl anilines using PhIO as a sole additive under ambient conditions. This methodology did not require any external additives and delivered anthranils in excellent yields with broad substrate scope. The mechanistic studies suggest that the reaction proceeds via in‐situ generation of iminoiodane leading to nitrene and a subsequent nucleophilic attack from oxygen of ortho‐carbonyl aniline on nitrene results in heterocyclization.
A unique lactonization of 2-methyl-3-acyl-4-phenylquinolines using PhIO as the oxidant and selectfluor as an additive is reported. The reaction occurs under ambient conditions through tandem oxidation and cyclization of sp 3 C−H bonds under metal-free conditions. The heterocycle-fused lactones are obtained in moderate to good yield.
An unprecedented tandem ortho‐selective fluorination and 1,3‐carbonyl migration in ortho‐carbonyl anilines using selectfluorTM as the sole reagent is reported. The reaction is transition‐metal free, does not require any pre‐functionalization, takes place under ambient conditions, and yields ortho‐fluoroanilide derivatives in moderate to good yields. SelectfluorTM serves the dual purpose of fluorine source and assists 1,3‐carbonyl migration. The formation of proposed charge transfer (CT) complex between ortho‐carbonyl aniline (donor) and selectfluorTM (acceptor), and its role in enabling the observed ortho‐selectivity is supported by experimental and computational investigations. The single‐electron‐transfer (SET) in the complex results in the formation of (2‐amino‐3‐fluorophenyl)(phenyl)methanone intermediate, which on subsequent 1,3‐carbonyl migration forms ortho‐fluoroanilide in presence of F+ or in‐situ generated H+.
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