RSC Advances
Communication
Table 2 Synthesis of benzimidazoles via palladium CTH reduction–
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a
Reaction conditions: 2-nitroaniline (1.0 mmol), 10% Pd/C (0.5 mol%),
TEAF (4.0 equiv.) were heated at 150 ꢁC for 5 min under microwave
b
irradiation. Isolated yields were reported. Reaction was conducted
under 100 ꢁC for 12 min to avoid debenzylation, 15% of 4a was isolated.
Scheme 3 Formation of 1,4-benzodiazepine-2,5-diones.
fashion to give quinazoline products as expected. Instead,
intramolecular aminolysis of the methyl ester dominated and
afforded benzodiazepine compounds (6a–b).
In summary, we have discovered a highly efficient and
diversied one-pot method for the construction of benzimid-
azole, quinazolin-4(3H)-one and 1,4-benzodiazepine-2,5-dione
scaffolds from nitro arenes through a palladium-CTH reduc-
tion–condensation cascade in triethylamine–formic acid azeo-
tropic mixture (TEAF) under microwave irradiation. This
method features the unprecedented application of TEAF as a
multi-functional reaction medium which enabled highly effi-
cient construction of diverse heterocyclic products. Other
applications of this methodology are currently underway and
will be disclosed in due course.
Acknowledgements
This work was supported in part by the Natural Sciences
Foundation of Hubei Province (20141j0169) and Wuhan
University of Technology.
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