2,4-Bis(2-ethoxyphenyl)-3-azabicyclo[3.3.1]nonan-9-one

The asymmetric unit of the title compound, C24H29NO3, contains two independent molecules, which each exibit a twin-chair conformation with an equatorial orientation of the ortho-ethoxyphenyl groups but different dihedral angles [41.3 (1) and 24.1 (1)°] between the benzene rings. In the crystal, pairs of weak C—H⋯O hydrogen bonds link the two different independent molecules into dimers.


Comment
Nitrogen containing heterocycles are useful building-blocks of the construction of various pharmacologically important molecules. Since the 3-azabicyclononanes are displying diverse biological actions (Park et al., 2012a;Parthiban et al., 2010aParthiban et al., , 2010bParthiban et al., , 2011aJeyaraman & Avila, 1981), and the biological actions mainly depend on the stereochemistry of the molecules, the synthesis as well as stereochemical analysis of any biologically active molecules are of importance in the drug-design and drug-devlopement programs. Based on the above points, we synthesized the title compound, in order to examine the configurational and conformational status by single-crystal X-ray studies.
The two benzene rings in two independent molecules are inclined to each other with angles of 41.3 (1) and 24.1 (1)°, respectively. In the crystal, weak intermolecular C-H···O interactions (Table 1) link independent molecules into dimer.

Experimental
The 2,4-bis-(2-ethoxyphenyl)-3-azabicyclo[3.3.1]nonan-9-one was synthesized by a modified and an optimized double Mannich condensation in one-pot, using 2-ethoxybenzaldehyde (0.1 mol, 15.018 g/13.94 ml), cyclohexanone (0.05 mol, 4.90 g/5.18 ml) and ammonium acetate (0.075 mol, 5.78 g) in a 50 ml of absolute ethanol (Park et al., 2011). The mixture was gently warmed on a hot plate at 303-308 K (30-35° C) with moderate stirring till the complete consumption of the starting materials, which was monitored by TLC. After completion of the rection, the crude compound was separated by filtration and gently washed with 1:5 cold ethanol-ether mixture. X-ray diffraction quality crystals of the title compound were obtained by slow evaporation from ethanol.

Refinement
All hydrogen atoms were fixed geometrically and allowed to ride on the parent carbon atoms, with C-H = 0.93-0.98 Å and N-H = 0.86 Å, and with U iso (H) = 1.2-1.5U eq of the parent atom.

Figure 1
Two independent molecules of the title compound with atomic labels and displacement ellipsoids represented with 30% probability level. H atoms omitted for clarity.

2,4-Bis(2-ethoxyphenyl)-3-azabicyclo[3.3.1]nonan-9-one
Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 R-factors(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.   0.0457 (9) 0.0381 (9) 0.0504 (10) 0.0002 (7