Synthesis of isoxazoles and their hydrazinolysis to 5-aminopyrazoles: an approach to fluorescent derivatives

Abstract

A protocol for the synthesis of 5-arylisoxazoles and their TFA-mediated hydrazinolysis to 5-amino-3-aryl-1H-pyrazoles was developed using readily available ketones as starting materials and eco-friendly microwave-assisted conditions. All reactions proceeded in high yields, and although some of the obtained heteroamines are commercially available, they are challenging to obtain because they are expensive or require access to equally expensive substrates. A computational study using TD-DFT calculations was conducted to better understand the reaction mechanism of the isoxazole ring-opening reaction with hydrazine in water. Ultimately, the photophysical properties of some fluorescent products were conveniently explored.