Front Cover: Asymmetric Synthesis of Multi‐substituted Prolines via a Catalytic 1,3‐Dipolar Cycloaddition Using a Monocationic ZnIIOAc Complex of a Chiral Bisamidine Ligand, Naph‐diPIM‐dioxo‐R (ChemCatChem 22/2020)

Abstract

The Front Cover shows a highly efficient catalytic enantioselective 1,3-dipolar cycloaddition of tridentate-type α-imino esters and acrylates. In their Communication, I. N. Chaithanya Kiran et al. explain the catalyst's design concept and its performance for the reaction. The catalyst is a monocationic zinc acetate complex of a chiral bisamidine-type bidentate ligand. An anionic acetate ligand of the Lewis acidic Zn complex acts as a Brønsted base to facilitate a smooth intramolecular deprotonation to generate an imino N,O-cis-Zn enolate. The oxygen atoms of two dioxolanes of the ligand form a C2 chiral scaffold, in which the Zn enolate position is well controlled by a non-bonding n-π* interaction. The catalyst shows high activity, diastero-/enantio-/regio-selectivity, productivity, and broad generality. This reaction provides a path for the synthesis of pyrrolidine-containing chiral bioactive compounds, ligands and organocatalysts. More information can be found in the Communication by I. N. Chaithanya Kiran et al.