Cycloadditions and condensations as essential tools in spiropyrazoline synthesis

Heterocycles with potential bioactive properties are of greater interest to researchers engaged in the areas of natural product synthesis and heterocyclic methodology. Several FDA (Food and Drug Administration) approved pharmaceutical drugs incorporate a heterocyclic motif in their core structure. Spiroisoxazolines and spiropyrazolines belong to the class of five membered heterocycles that have received greater attention over the past four decades. Spiropyrazolines structurally resemble naturally occurring spiroisoxazolines, have extra nitrogen in place of isoxazoline oxygen, and offer the viability to construct useful analogs for the exploration of possible bioactivity. As of today, no reports on the construction of these spiropyrazolines were available and the current review is aimed at providing a comprehensive discussion of the protocols applied in the synthesis of functionalized spiropyrazolines.

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► Heterocycles with potential bioactive properties are of greater interest to organic and medicinal chemists.
► Several FDA approved pharmaceutical drugs incorporate a heterocyclic ring in their core molecular structure.
► Spiroisoxazolines and spiropyrazolines have received a greater attention during the last four decades.
► No review reports were documented on the synthesis of spiropyrazoline ring systems.
► Current review provides a discussion on methodologies to synthesize functionalized spiropyrazolines.