Abstract
Arylhydrazones of 2-bromobenzaldehydes and its analogs are cyclized in PEG-400 at 110 °C in the presence of a catalytic amount of copper powder along with NaOtBu to give 1-aryl-1H-indazole derivatives in good yields.
GRAPHICAL ABSTRACT
ACKNOWLEDGMENT
This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science, and Technology (2011-0005123).
Notes
a Reaction conditions: 1a (0.5 mmol), copper catalyst (0.05 mmol), base (1 mmol), solvent (5 mL), 110 °C, under N2.
a Reaction conditions: 1 (0.5 mmol), Cu powder (0.05 mmol), NaO t Bu (1 mmol), PEG-400 (3 mL), 110 °C, under N2.