Λ-[Co((S, S)-dpen)3]3+ 2I-B(C6F5)4-: A Second Generation Air- and Water-Stable Chiral Solvating Agent for Chirality Sensing (dpen = NH2CHPhCHPhNH2)

Motahareh Alimohammadi; Alireza Hasaninejad; Quang H Luu; John A Gladysz

doi:10.1021/acs.joc.0c01332

Λ-[Co((S, S)-dpen)₃]³⁺ 2I^-B(C₆F₅)₄^-: A Second Generation Air- and Water-Stable Chiral Solvating Agent for Chirality Sensing (dpen = NH₂CHPhCHPhNH₂)

J Org Chem. 2020 Sep 4;85(17):11250-11257. doi: 10.1021/acs.joc.0c01332. Epub 2020 Aug 19.

Authors

Motahareh Alimohammadi¹, Alireza Hasaninejad¹, Quang H Luu¹, John A Gladysz¹

Affiliation

¹ Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, United States.

PMID: 32663026
DOI: 10.1021/acs.joc.0c01332

Abstract

When CDCl₃ solutions of chiral racemic molecules containing moderately Lewis basic functional groups are treated with the chiral solvating agent (CSA) Λ-[Co((S,S)-dpen)₃]³⁺ 2I^-B(C₆F₅)₄^- (Λ-(S,S)-1³⁺ 2I^-B(C₆F₅)₄^-), baseline-resolved NMR signals are observed for the enantiomers (29 diverse analytes). Only 0.62-100 mol % loadings are required (avg 14.5 or 11.6% for 24 analytes common to all tested CSAs). The overall performance is superior to those reported earlier for analogous salts with 2X^-BAr_f^- counter anion sets [BAr_f = B(3,5-C₆H₃(CF₃)₂)₄]; 1.0-100 mol % loadings, avg 32.6% (X = Cl) or 14.0% (X = I) for 24 common analytes) and a new 2TfO^-B(C₆F₅)₄^- salt (1.1-100 mol % loadings; avg 31.0% for 24 common analytes), including extensions to prochirality sensing. The effect of the solvent (Δδ in CDCl₃ > CD₂Cl₂) is analyzed. The new CSAs are prepared in two steps from Λ-(S,S)-1³⁺ 3Cl^- by standard anion metathesis recipes (90-98% overall). The broad analyte scope and modest loading requirements for the title CSA distinctly surpass those of others in the literature.