New three-component domino reactions,
providing divergent approaches
to multifunctionalized pyrroles with different substitution patterns,
have been established (47 examples). In this work, a new rearrangement
of quinoxalinones with the participation of the in situ-generated 2-en-1-imine moiety of the substituent at C3 makes it
possible to construct two new heterocyclic systems, namely, a benzimidazolone
and a pyrrole, simultaneously under one-pot reaction conditions. The
reaction is easy to perform simply by mixing three common reactants
of acetic acid with heating. Secondary amines or primary alcohols
as the third component of the reaction, along with quinoxalin-3(4H)-ones and malononitrile, not only initiate the rearrangement
but also are responsible for the nature of substituents at position
5 of the pyrrole ring in the newly formed new biheterocyclic system.
The reaction proceeds smoothly and can be finished within 7 h, which
makes workup convenient to give up to 97% chemical yields.
A new process has been developed for the bromine-promoted
sequential
(sp2)C = (sp2)C bond functionalization of (E)-3-styrylquinoxalin-2(1H)-ones and furo[b]annulation via the 5-exo-cyclization
in dimethyl sulfoxide (DMSO). The reaction represents a novel strategy
for the synthesis of 2-aryl-3-(methylthio)furo[2,3-b]quinoxalines and involves 3-(1,2-dibromo-2-arylethyl)quinoxalin-2(1H)-ones and 2-arylfuro[2,3-b]quinoxalines
as key intermediates. Furthermore, DMSO was converted to dimethyl
sulfide in situ, which served as the methylthiolation reagent in the
reaction. This protocol constitutes an efficient and convenient method
for the annulation and methylthiolation of (E)-3-styrylquinoxalin-2(1H)-ones bearing a wide range of functional groups in high
yields at room temperature.
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