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

Abstract

The asymmetric [3 + 2] cycloaddition of 4-amino pyrazolone-derived azomethine ylides with α,β-enones has been established for the synthesis of 4-spiropyrazolones derivatives with four contiguous stereocenters. This cycloaddition process delivered spiro[pyrrolidine-2,4′-pyrazolone] derivatives in high yields with excellent stereoselectivities (up to 95% yields, >20 : 1 dr and >99% ee) under mild conditions.