Asymmetric Synthesis of 1-(Diarylmethyl)-pyrazolidin-3-ones

Significance

Azomethine imines are widely used 1,3-dipoles in [3+2] cycloadditions with alkenes and alkynes. In this work the authors present the use of azomethine imines of type 1 in the asymmetric synthesis of 1-(diarylmethyl)pyrazolidin-3-ones (2) through a rhodium-catalyzed nucleophilic arylation. It was found that sodium-tetraarylborates could be efficiently used as nucleophiles. Furthermore, there is evidence that the triarylborane released during the catalytic cycle activates the substrate by acting as a Lewis acid.