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Extending the scope of enantiomer resolution by complexation gas chromatography


Journal of the American Chemical Society 104(26): 7573-7580
Extending the scope of enantiomer resolution by complexation gas chromatography
Nickel(II) bis[(1R)-3-(heptafluorobutyryl)camphorate] (3b) is an efficient optically active statonary phase for the quantitative gas chromatographic resolution of racemic alkyl-substituted cyclic ethers containing rings of up to 6 members (6-16), the cyclic ketone trans-2,5-dimethylcyclopentanone, and the aliphatic alcohol tert-butylmethylcarbinol. Thermodynamic parameters of enantiomer discrimination, i.e., -.DELTA.S,R(.DELTA.G.degree.), between 10 cyclic ethers (6-15) and 3b are reported and discussed. The molecular configurations of the invertomers of 1-chloro-2,2-dimethylaziridine (21) eluting on 3b are assigned by indirect evidence, and for the first time, enantiomerization of 21 and 1,6-dioxaspiro[4.4]nonane on the metal chelates 3a and 3b, respectively, is chromatographically detected. The racemic alkyl-substituted thiranes and thietanes 23-26 are quantitatively resolved on 3b. A quadrant rule, which correlates molecular configuration and chromatographic elution order on 3b, derived from (+)-(1R)-camphor, is valid for alkyl-substituted oxiranes; however, a notable exception is found for trans-2,3-dimethylthiirane (25). The absence of racemization in the preparation of trans-(1S,2S)-1-chloro-2-methylaziridine (22) from (S)-alanine and in the conversion of trans(2S,3S)-2,3-dimethyloxirane (11) to trans-(2R,3R)-2,3-dimethylthiirane (25) with inversion of configuration is proved by complexation gas chromatography. Neither substrate derivatization nor isolation and purification are necessary for the chromatographic determination of enantiomeric compositions (ee), and 10 ng of sample is required for the assignment of molecular configurations.

Accession: 005432759

DOI: 10.1021/ja00390a031

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