Syntheses of chiral nopinane-annelated pyridines of C₂ and D₂-symmetry: X-ray structures of the fused derivatives of 4,5-diazafluorene, 4,5-diaza-9H-fluoren-9-one, and 9,9’-bi-4,5-diazafluorenylidene

Reaction of (+)-pinocarvone oxime with 2-morpholinocyclopent-2-enone and FeCl₃·6H₂O affords chiral C₂-symmetric fused derivative of 4,5-diazafluorene, whose oxidation with SeO₂ gives nopinane-annelated derivatives of 4,5-diaza-9Hfluoren- 9-one (C₂-symmetry) and of 9,9’-bi-4,5-diazafluorenylidene (D₂-symmetry). Structures of the compounds synthesized were proved by X-ray crystallography.