Copper Powder–Catalyzed C-N Bond Formation of Arylhydrazones of 2-Bromobenzaldehydes Leading to 1-Aryl-1H-indazoles

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 NaO^tBu to give 1-aryl-1H-indazole derivatives in good yields.

GRAPHICAL ABSTRACT

Keywords:

• 1-Aryl-1H-indazoles
• arylhydrazones
• C-N bond formation
• copper powder

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.