Diastereoselective synthesis of indolenine-based spiro[pyrazolone-4,2′-pyrrolidine] scaffolds via 1,3-dipolar cycloaddition of 4-aminopyrazolones, aldehydes, and indolenines

Abstract

In this work, we report a novel one-pot [3+2] cycloaddition of 4-aminopyrazolones, indolenines, and aldehydes. The reaction utilized the in-situ generated azomethine ylides as 1,3-dipoles and 2-alkenylindolenines as dipolarophiles affording...

Asymmetric 1,3-dipolar cycloaddition of 4-amino pyrazolone-based azomethine ylides: a straightforward approach to spiropyrazolones

“…Considering the well-established competence of azomethine ylide species in 1,3-dipolar cycloaddition processes en route to chiral pyrolidines, 10 we envisaged the utilization of 4-amino pyrazolones for in situ generation of pyrazolone-based azomethine ylides and demonstrated their application in [3 + 2] and [3 + 3] cyclizations. 11,12 However, no asymmetric version of the reactions has been achieved. In order to explore the synthetic utility of 4-amino pyrazolones in asymmetric transformations thus extending the structural diversity of chiral spiropyrazolones, herein we report a three-component asymmetric [3 + 2] spiroannulation process enabled by chiral phosphoric acid catalysis (Scheme 1c).…”