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Integration of Catalysis and Analysis is the Key: Rapid and Precise Investigation of the Catalytic Asymmetric Gosteli-Claisen Rearrangement

Troendlin, J., Rehbein, Julia, Hiersemann, M. and Trapp, O. 2011. Integration of Catalysis and Analysis is the Key: Rapid and Precise Investigation of the Catalytic Asymmetric Gosteli-Claisen Rearrangement. Journal of the American Chemical Society 133 (41) , pp. 16444-16450. 10.1021/ja207091x

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Abstract

The kinetics of the CuII(bisoxazoline)-catalyzed diastereo- and enantioselective Gosteli–Claisen rearrangement of 2-alkoxycarbonyl-substituted allyl vinyl ethers has been investigated by enantioselective on-column reaction gas chromatography (ocRGC). Enantioselective ocRGC integrates (stereoselective) catalysis and enantioselective chromatography in a single microcapillary, which is installed in a GC-MS for direct analysis of conversion and selectivity. Thus, this technique allows direct differentiation of thermal and stereoselectively catalyzed reaction pathways and determination of activation parameters and selectivities of the individual reaction pathways starting from stereoisomeric reactants with high precision. Two modes of operation of enantioselective ocRGC are presented to investigate noncatalyzed, i.e., conversion of isopropyl-2-(allyloxy)but-2Z-enoate 1 to isopropyl-3R,S-methyl-2-oxy-hex-5-enoate (±)-2 and the [Cu{(R,R)-Ph-box}](SbF6)2-catalyzed Gosteli–Claisen rearrangement, i.e., conversion of isopropyl-2-(but-2′E-en-1-yloxy)but-2Z-enoate (E,Z)-3 to isopropyl-3S,4S-dimethyl-2-oxy-hex-5-enoate 4b. Eyring activation parameters have been determined by temperature-dependent measurements: Uncatalyzed rearrangement of 1 to (±)-2 gives ΔG (298 K) = 114.1 ± 0.2 kJ·mol–1, ΔH = 101.1 ± 1.9 kJ·mol–1, and ΔS = −44 ± 5 J·(K·mol)−1, and catalyzed rearrangement of (E,Z)-3 to 4b gives ΔG (298 K) = 101.1 ± 0.3 kJ·mol–1, ΔH = 106.1 ± 6.6 kJ·mol–1, and ΔS = 17 ± 19 J·(K·mol)−1.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Publisher: ACS Publications
ISSN: 0002-7863
Last Modified: 19 Mar 2016 22:21
URI: http://orca-mwe.cf.ac.uk/id/eprint/13008

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