Determining the enantioselectivity of chiral catalysts by mass spectrometric screening of their racemic forms

Journal of the American Chemical Society

Volumn 133, Issue 13, 2011, Pages 4710-4713

  Ebner, Christian ^a   Müller, Constanze A ^a   Markert, Christian ^a   Pfaltz, Andreas ^a  

^a UNIVERSITY OF BASEL   (Switzerland)

Author keywords

[No Author keywords available]

Indexed keywords

CATALYST STRUCTURES; CHIRAL CATALYST; MASS SPECTROMETRIC SCREENING;

ENANTIOSELECTIVITY; MASS SPECTROMETERS; SPECTROMETRY;

CATALYSTS;

DICHLOROMETHANE;

ARTICLE; CATALYST; CHEMICAL STRUCTURE; DIELS ALDER REACTION; ELECTROSPRAY MASS SPECTROMETRY; ENANTIOSELECTIVITY; MASS SPECTROMETRY; MICHAEL ADDITION;

CATALYSIS; MASS SPECTROMETRY; MOLECULAR STRUCTURE; ORGANOMETALLIC COMPOUNDS; STEREOISOMERISM;

EID: 79953856934     PISSN: 00027863     EISSN: 15205126     Source Type: Journal    
DOI: 10.1021/ja111700e     Document Type: Article

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19. The error margins in the data of the less selective catalysts (ligands 4a and 4b) are relatively high because the difference between the measured signal ratio, I (3a)/ I (3b), and the ratio of quasienantiomeric substrates, Q, is extremely small in the 0-30% ee range [e.g., for 20% ee and Q = 25:75, I (3a)/ I (3b) is 26:74]. Consequently, small measurement errors lead to large errors in the calculated ee values. In five reactions, the ee values for 4a varied from 17 to 26% (see Table 1 in the SI). Values in the 50-100% ee range are much more accurate because they are based on a substantially larger difference between the signal ratio and Q. For ligand 4e, the values from four screening experiments were between 61 and 62% ee (see Table 1 in the SI).
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26. We thank one of the reviewers for suggesting these experiments.