Abstract
Troger's base 1 (2,8-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine) undergoes enantiomerization in the gas and liquid phases. By enantioselective stopped-flow multidimensional gas chromatography, Eyring activation parameters of the enantiomerization barrier have been determined in the inert mobile gas phase (helium): ΔG⧧gas(298.15 K) = 112.8 ± 0.5 kJ mol-1; ΔH⧧gas = 62.7 ± 0.3 kJ mol-1; ΔS⧧gas = −168 ± 6 J (K mol)-1. An enantiomerization pathway proceeding via a degenerated retro-hetero-Diels−Alder ring opening or formation of a zwitterionic structure of 1 is proposed. By enantioselective dynamic gas chromatography, Eyring activation parameters have also been determined via computer-aided simulation of experimental interconversion peak profiles in the chiral stationary liquid phase: ΔG⧧liq(298.15 K) = 117.8 ± 0.5 kJ mol-1; ΔH⧧liq = 48.9 kJ mol-1; ΔS⧧liq = −231 ± 8 J (K mol)-1. Surprisingly, in the presence of the chiral stationary phase (CSP) Chirasil-β-Dex, required for enantiomer separation o...
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