Kinetic Resolutions of Azomethine Imines via Copper-Catalyzed [3 + 2] Cycloadditions

Abstract

An effective method has been developed for the kinetic resolution of racemic azomethine imines via [3 + 2] cycloadditions with alkynes catalyzed by a chiral copper complex. Efficient kinetic resolution is observed for a variety of N1 and C5 substituents on the dipole, thereby furnishing a wide array of useful enantioenriched azomethine imines, which can readily be transformed into monocyclic and bicyclic pyrazolidinones.

Ferrocene-derived P,N ligands: synthesis and application in enantioselective catalysis

“…In an extension of this method, it has been shown that the same catalyst system is also effective in the kinetic resolution of racemic azomethine imines rac-65 (Scheme 17) [86]. As a result, a wide variety of enantioenriched 1,3-dipoles 65 could be isolated.…”

N‐Imide Ylide‐Based Reactions: CH Functionalization, Nucleophilic Addition and Cycloaddition

“…This copper(I)-catalyzed asymmetric cycloaddition was employed in the kinetic resolution of racemic azomethine imine 175 by using phenyl-substituted phosphaferrocene oxazoline L 17 as the ligand, leading to chiral azomethine imine 176 (Scheme 31). [62] By altering the catalyst to copper bis(trimethylsilyl)amide (CuHMDS) and (S)-DIP-BINAP L 10 , Kobayashi and co-workers reported another example for the copper-catalyzed 1,3-dipolar cycloaddition, affording 5,7-disubstituted pyrazolo-A C H T U N G T R E N N U N G [1,2-a]pyrazolones 162 exclusively. In this transformation, the regioselectivity was reversed compared with the results reported by Fu and co-workers.…”

Applications of Aza‐ and Phosphaferrocenes and Related Compounds in Asymmetric Catalysis

“…(34)), thereby furnishing enantioenriched azomethine imines that can be transformed into a variety of pyrazolidinones (Eq. (35) and (36)) [76]. Phosphaferrocene-oxazoline 75 provided the highest selectivity factors among an array of chiral ligands that were examined.…”