4-Nitroisoxazolin-5(2H)-one (nitroisoxazolone) has multiple functionalities embedded as the partial structures that include a nitroalkene, an enamine, a lactone, a N-O bond, and an α, β-unsaturated carbonyl moiety. These structural features facilitate versatile chemical transformations that lead to polyfunctionalized heterocycles that are not easily available by alternative methods. Anionic nitroisoxazolone readily undergoes ring opening to afford dianionic cyano-aci-nitroacetate. This dianionic reagent serves as a safe cyano(nitro)methylating agent to afford glutaronitriles and α-nitro-δ-keto nitriles that are precursors of polyfunctionalized isoxazolines, pyridines, and diazabicycliccompounds. On the other hand, functionalized nitroenamines and amidoximes are obtained through the ring opening reactions of N-methylnitroisoxazolone with amines. The nitroisoxazolone also generates carbamoylnitrile oxide upon treatment with water, which undergoes 1,3-dipolar cycloadditions with alkynes, alkenes, nitriles, and 1,3-dicarbonyl compounds to efficiently yield functionalized isoxazol(in)es and oxadiazoles. When nitroisoxazolone is treated with the enolates of 1,3-dicarbonyl compounds, the ring transformations proceeds to afford 3,4-difunctionalized pyrroles. Interesting concepts, such as pseudo-intramolecular processes, intramolecular ring transformations, and inverse-electron-demand 1,3-dipolar cycloadditions are also developed accompanied by the syntheses of versatile heterocyclic systems.