Synthesis, resolution, and VCD analysis of an enantiopure diazaoxatricornan derivative.
Using simple organic synthetic transformations, a novel diazaoxatricornan derivative, the 12 c-methyl-12-phenyl-8-propyl-12,12 c-dihydro-8 H-4-oxa-8,12-diazadibenzo[ cd, mn]pyrene ( 6a), was prepared. This novel chiral cup-shaped molecule was isolated in racemic form and in excellent yield after the addition of methyl lithium to the BF 4 salt of a novel unsymmetrical diazaoxatriangulenium cation. Compound 6a was found to be stable under classical laboratory conditions-something not obvious considering the extreme stability of the carbenium ion precursor, the electron-rich nature of the core, and the strain induced by the pyramidalization of the central carbon. The enantiomers were readily separated by chiral stationary phase chromatography, and the absolute configuration of (-)-( S)- 6a was determined by a comparison of the experimental and theoretical vibrational circular dichroism (VCD) spectra. This isolation of (-)-( S)- 6a and (+)-( R)- 6a constitutes thus the first report of a nonracemic closed-capped chiral bowl molecule for which the chirality is due to the intrinsic dissymmetry of the central core of the structure only.
Mobian
Pierre
P
Department of Organic Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland.
Nicolas
Cyril
C
Francotte
Eric
E
Bürgi
Thomas
T
Lacour
Jérôme
J
D031242:Agrostemma; D001372:Aza Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D001580:Benzopyrenes / Q000138:chemical synthesis* / Q000737:chemistry; D002942:Circular Dichroism; D008958:Models, Molecular; D008968:Molecular Conformation; D013055:Spectrophotometry, Infrared; D013237:Stereoisomerism; D013816:Thermodynamics
D001372:Aza Compounds; D001580:Benzopyrenes