Journal of Organic Chemistry p. 5279 - 5283 (1995)
Update date:2022-08-11
Topics:
Boone, Harold W.
Bruck, Michael A.
Bates, Robert B.
Padias, Anne Buyle
Hall, H. K.
Model compounds for polyaromatic quinone imines were synthesized and characterized by variable-temperature 1H NMR spectroscopy and X-ray single crystal structure determination.N,N'-Diphenyl-1,4(5)-dimethoxyanthraquinone 9,10-diimines were synthesized by condensing 2 equiv of aniline with 1,5-dimethoxyanthraquinone (15DMAQ) and 1,4-dimethoxyanthraquinone (14DMAQ), respectively, in the presence of titanium tetrachloride and 1,4-diazabicyclo<2.2.2>octane (DABCO).The X-ray single crystal structure determination of the diimine of 15DMAQ is reported.The condensation of aniline with anthraquinones results in a buckling of the anthraquinone ring system, giving it a "butterfly" conformation while the diimine of 15DMAQ has an anti configuration with the N-phenyl rings lying above the methoxy substituents.The diimine of 14DMAQ has a syn configuration, again with these N-phenyl rings lying above the methoxy substituents.The symmetrical structural butterfly conformations of the diimines allowed for the observation of a dynamic butterfly inversion by variable-temperature 1H NMR spectroscopy.The energy barriers for the butterfly inversion of N-phenyl 15DMAQ and 14DMAQ diimines are 9.5 kcal/mol.The implications of the crystal structure and molecular dynamics for the polymeric structures are discussed.
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