Tetrabutylammonium Bromide (TBAB) Promoted Metal-Free Synthesis of 2H-Indazolo[1,2-b]Phthalazinetriones and Pyrazolo[1,2-b]Phthalazines from Benzylalcohol through Aerobic Oxidation, Sequential Addition-Cyclization with Phthalhydrazide and β-Diketones

Abstract

A solvent-free synthesis of 2H-indazolo[1,2-b]phthalazinetriones 4 and pyrazolo[1,2-b]phthalazines 6 scaffolds using benzyl alcohol 1 via TEMPO/CAN and TBAB mediated aerobic oxidation, sequential addition-cyclization with phthalhydrazide 2 and β-diketones 3,5 is reported. The experimental strategy offers several advantages, such as simple workup, inexpensive chemicals without any use of solvents, and short reaction time.

Graphical abstract

Keywords:

• Solvent-free synthesis
• cyclization reaction
• metal-free synthesis
• tetrabutylammonium bromide using additive
• catalyst
• ambient temperature
• easy work up and short reaction time

Acknowledgments

The authors wish to express their gratitude to the Vellore Institute of Technology, Vellore for support and facilities and SIF-VIT for providing analytical support.