Regioselective Synthesis of 1,3,5-Trisubstituted Pyrazoles

Abstract

A new and a simple approach toward synthesis of 1,3,5-trisubstituted pyrazoles from chalcone arylhydrazones via oxidative cyclization has been achieved. 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone was successfully used as an oxidizing agent to give excellent yields of pyrazoles.

GRAPHICAL ABSTRACT

Keywords:

• Chalcones
• hydrazones
• oxidative cyclization
• pyrazoles
• regioselective

ACKNOWLEDGMENT

The authors thank the Department of Science and Technology, government of Goa, for financial assistance.

Notes

^a Conditions: N-Arylhydrazones, DDQ (2 equivalents), dichloromethane, rt, stir, 2 h.

^b Yields after recrystallization.

^c Determined mp compared to lit. mp.^{[3f,4b,8–15,17–19]}

^a Conditions: N-Arylhydrazones, DDQ (2 equivalents), dichloromethane, rt, stir, 2 h.

^b Yields after recrystallization.

^c Determined mp compared to lit. mp.^[4b,15,16]