Enantiomeric impurities in chiral catalysts, auxiliaries, and synthons used in enantioselective syntheses. Part 4

Armstrong, Daniel W.; Lee, Jauh T.; Chang, Lisa W.

doi:10.1016/j.tetasy.2013.07.019

Cited by 15 publications

(21 citation statements)

References 97 publications

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“…This procedure for quantification of enantiomeric impurities cannot be used when impurity concentrations are lower (<0.1%). To determine concentrations at such lower levels, a similar procedure mentioned in previous reports was used . The trace enantiomeric impurities were determined by injecting the high concentrations of the enantiomer to overload the column, and the area of the largest peak was underestimated.…”

Section: Resultsmentioning

confidence: 99%

“…Each year new chiral reagents become commercially available, contributing to significant advances in synthesis of asymmetric compounds. Thus, an understanding of the enantiomeric composition of chiral starting materials remains essential, particularly since there is rarely any indication of their enantiomeric purity . Further, simple assays to check or confirm enantiomeric impurities of commercial catalysts/synthons/auxiliaries are seldom provided.…”

Section: Introductionmentioning

confidence: 99%

“…Further, simple assays to check or confirm enantiomeric impurities of commercial catalysts/synthons/auxiliaries are seldom provided. These analysis methods can be essential since it is known that there can be considerable batch‐to‐batch variability in enantiomeric purity of the same reagent from the same supplier …”

Section: Introductionmentioning

confidence: 99%

“…Also, it is known that the effects of enantiomeric impurities in reagents can produce nonproportional ees in products (aka nonlinearity) . Previously, we reported the enantiomeric impurities of more than 300 commercial chiral compounds and efficient chromatographic methods for their analysis . Several compounds had high ees (>99%) while some had low to high percent levels of enantiomeric impurities …”

Section: Introductionmentioning

confidence: 99%

“…Herein, we discuss the analyses of 51 chiral compounds, reagents, synthons, and auxiliaries that have not been assessed previously and/or have been introduced after 2013, when the last comprehensive evaluation of commercial chiral compounds was reported …”

Section: Introductionmentioning

confidence: 99%

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Enantiomeric impurities in chiral catalysts, auxiliaries, and synthons used in enantioselective syntheses. Part 5

et al. 2019

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The enantiomeric excess of chiral starting materials is one of the important factors determining the enantiopurity of products in asymmetric synthesis. Fifty‐one commercially available chiral reagents used as building blocks, catalysts, and auxiliaries in various enantioselective syntheses were assayed for their enantiomeric purity. The test results were classified within five impurities level (ie, <0.01%, 0.01%‐0.1%, 0.1%‐1%, 1%‐10%, >10%). Previously from 1998 to 2013, several reports have been published on the enantiomeric composition of more than 300 chiral reagents. This series of papers is necessitated by the fact that new reagents are forthcoming and that the enantiomeric purity of the same reagent can vary from batch to batch and/or from supplier to supplier. This report presents chiral liquid chromatography (LC) and gas chromatography (GC) methods to separate enantiomers of chiral compounds and evaluate their enantiomeric purities. The accurate and efficient LC analysis was done using newly introduced superficially porous particle (SPP 2.7 μm) based chiral stationary phases (TeicoShell, VancoShell, LarihcShell‐P, and NicoShell).

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Enantiomeric impurities in chiral catalysts, auxiliaries, and synthons used in enantioselective syntheses. Part 5

et al. 2019

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Recent advances in the field of chiral crystallization

Putman

Armstrong

2022

Chirality

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Crystallization is one of the largest and most economical bulk purification techniques used in industry today. There has been an increase in demand for enantiomerically pure compound production for research, organic synthesis, pharmaceutical drug production, and other applications. Even after asymmetric synthesis, chiral purification will always be necessary. The focus of this review is on recent advances in chiral crystallization for the purification of enantiomers. A comprehensive discussion of three techniques and their mechanisms is provided, namely: attrition‐enhanced deracemization, cocrystallization, and inorganic ionic cocrystallization. Several examples of attrition‐enhanced deracemization are discussed. The key advantage of this technique is that it eliminates enantiomeric waste and can be used to produce enantiomeric excesses of greater than 99% from racemic mixtures. Chiral cocrystallization is examined, with over 60 cocrystallizing compounds, as an excellent means for enantiomeric enrichment. Selective chiral inclusion complexation was shown to be a novel approach for the formation of cocrystals. Chiral inorganic ionic cocrystallization is a new technique involving the formation of cocrystals between chiral ligands and certain metal salts in order to produce conglomerate crystal behavior in otherwise racemic compounds.

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Cyclofructans as Chiral Selectors: An Overview

Hellinghausen

Armstrong

2019

Methods in Molecular Biology

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Enantiomeric impurities in chiral catalysts, auxiliaries, and synthons used in enantioselective syntheses. Part 4

Cited by 15 publications

References 97 publications

Enantiomeric impurities in chiral catalysts, auxiliaries, and synthons used in enantioselective syntheses. Part 5

Enantiomeric impurities in chiral catalysts, auxiliaries, and synthons used in enantioselective syntheses. Part 5

Recent advances in the field of chiral crystallization

Cyclofructans as Chiral Selectors: An Overview

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