Isoxazol-5-ones as Strategic Building Blocks in Organic Synthesis

Isoxazol-5-one rings have been identified as relevant motifs in drug candidates, agrochemicals, and materials. Furthermore, this heterocycle has been also applied as a versatile building block for the preparation of a variety of densely functionalized molecules. This short review will present the most representative applications of isoxazol-5-ones in organic synthesis while discussing their properties and reactivity. 1 Introduction 1.1 General Aspects 1.1.1 Tautomerism 1.1.2 Importance: Natural Products Isolation, Biological Activity, and Materials 1.1.3 Preparation Methods 2 Isoxazol-5-ones in Organic Synthesis 2.1 General Reactivity 2.2 Specific Examples 2.2.1 Alkylation Strategies 2.2.2 Alkyne Synthesis 2.2.3 Annulation Reactions 2.2.4 N–O Bond Insertions 2.2.4.1 Preparation of 1,3-Oxazin-6-ones 3 Conclusions