Novel cis–trans enantiomeric conglomerates: triage and absolute configurations via anomalous X-ray scattering. A photochemical second order asymmetric transformation

Three tricyclic imides were prepared by a Diels–Alder reaction of 6-arylfulvenes and maleic anhydride, followed by treatment with NH3. The exo isomers were found to exist as conglomerates when the aryl group was either p-tolyl or p-anisyl (although not phenyl). Triage of the p-tolyl racemate, followed by reaction with p-toluenesulfonyl chloride in CH2Cl2/Et3N, led to the crystalline enantiopure N-tosylimides (these were also conglomerates). X-ray diffraction analysis of the N-tosylimides via the anomalous dispersion technique led to assignment of the absolute configurations (as either E or Z). The original p-tolyl imide enantiomers were found to racemize under UV irradiation in CHCl3. Based on this, a possible second order asymmetric transformation under photochemical conditions was attempted, and indeed led to the isolation of crystalline imide with a small ee (∼15%).

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((10-11)E,2R,6S)-10-((4-Methylphenyl)methylene)-4-azatricyclo(5.2.1.02,6)-dec-8-ene-3,5-dioneEe >95%[α]D25=+59.8 (c 1.9, CHCl3)Source of chirality: resolution (triage)Absolute configuration: (10-11)E,2R,6S

((10-11)Z,2R,6S)-10-((4-Methylphenyl)methylene)-4-azatricyclo(5.2.1.02,6)-dec-8-ene-3,5-dioneEe >95%[α]D25=-57.5 (c 1.9, CHCl3)Source of chirality: resolution (triage)Absolute configuration: (10-11)Z,2R,6S

((10-11)E,2R,6S)-4-(p-Toluenesulfonyl)-10-((4-methylphenyl)methylene)-4-azatricyclo(5.2.1.02,6)-dec-8-ene-3,5-dioneEe >95%[α]D25=+136.9 (c 1.3, CHCl3)Source of chirality: resolution (triage)Absolute configuration: (10-11)E,2R,6S

((10-11)Z,2R,6S)-4-(p-Toluenesulfonyl)-10-((4-methylphenyl)methylene)-4-azatricyclo(5.2.1.02,6)-dec-8-ene-3,5-dioneEe >95%[α]D25=-120.0 (c 2.0, CHCl3)Source of chirality: resolution (triage)Absolute configuration: (10-11)Z,2R,6S