Tetrahydropyridinium bromide: Useful synthon to functionalized pyrrolidines

A three-component, general and practical route for diastereoselective synthesis of aza-spirocyclic pyrazolones via a decarboxylative annulation process

An efficient, general, and practical route for highly diastereoselective synthesis of aza-spirocyclic pyrazolones from easily available α-amino acids, aldehydes, and alkylidene pyrazolones by means of a decarboxylative annulation process is reported.

Enantioselective [3 + 2] annulation of 4-isothiocyanato pyrazolones and alkynyl ketones under organocatalysis

An asymmetric [3 + 2] annulation reaction of 4-isothiocyanato pyrazolones with alkynyl ketones is developed, providing expeditious access to spiro[pyrroline–pyrazolones].

A Neber approach for the synthesis of spiro-fused 2H-azirine-pyrazolone

A base-mediated Neber reaction of enaminopyrazolones with sulfonyl chlorides was developed and various spiro-fused 2H-azirine-pyrazolones were obtained in good yield.

Phosphine-catalyzed [4 + 2] cycloaddition of unsaturated pyrazolones with allenoates: a concise approach toward spiropyrazolones

Phosphine-catalyzed [4 + 2] cycloaddition of unsaturated pyrazolones with allenoates providing concise access to spiropyrazolones.