1,3-Diphenyl-3,4-dihydrobenzo[b][1,6]naphthyridine

The title compound, C24H18N2, is the first structural example containing the 3,4-dihydrobenzo[b][1,6]naphthyridine fragment. It was synthesized from 2,4,6,8-tetraphenyl-3,7-diazabicyclo[3.3.1]nonan-9-one and was crystallized from a methanol–ethanol solution over two years as a racemate. The C=N double bond [1.2868 (15) Å] is bent significantly out of the plane of the aromatic bicyclic ring system [N—C—C—C = −157.63 (12)°] and out of the plane of the phenyl ring bonded at the 1-position [N—C—C—C = 41.15 (16)°].


Experimental
Synthesis: 2,4,6,8-Tetraphenyl-3,7-diazabicyclo[3.3.1]nonan-9-one (1.34 g, 3.0 mmol) was dissolved in concentrated sulfuric acid (4 ml) under stirring and cooling and by use of an ultrasonic bath. This takes some time and the solution comes up to room temperature during this process. When the substance is completely dissolved, NaN 3 (240 mg, 3,7 mmol) was added and the reaction mixture was stirred for 1 h at room temperature. It was quenched with ice water, the yellow solution was extracted 3 times with ether to remove non basic impurities and then alkalized with 2 M NaOH solution. Then it was extracted 5 times with CH 2 Cl 2 , the organic layers were combined, washed 3 times with water, dried (Na 2 SO 4 ), filtered and the solvent removed in vacuo. The residue was dissolved in benzene and filtered and the solvent removed in vacuo. Finally, the residue was dissolved in the minimum amount of hot ethanol and the solution left for crystallization for 2 days. The formed needles were sucked off and dried giving pure 1,3-diphenyl-1,2,3,4-tetrahydro-benzo

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds supplementary materials sup-3 in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.
The non-hydrogen atoms were refined with anisotropic displacement parameters without any constraints. The H atom of the tertiary C-H group was refined with an individual isotropic displacement parameter and all X-C-H angles equal at a C-H distance of 1.00 Å (AFIX 13 of SHELXL-97). The H atoms of the CH 2 group were refined with common isotropic displacement parameters and idealized geometry with approximately tetrahedral angles and C-H distances of 0.99 Å (AFIX 23 of SHELXL-97). The H atoms of the phenyl rings as well as the atoma H6, H7, H8, and H9 were put at the external bisector of the C-C-C angle at a C-H distance of 0.95 Å and common isotropic displacement parameters were refined for the H atoms of the same ring (AFIX 43 of SHELXL-97).
The H atom H10 was put at the external bisector of the C-C-C angle at a C-H distance of 0.95 Å but the individual isotropic displacement parameter was free to refine (AFIX 43 of SHELXL-97).