(2RS,5′RS)-3′,4′-Bis(4-chlorophenyl)-3,4-dihydrospiro[acridine-2,5′(4′H)-[1,2]oxazol]-1(2H)-one

The title compound, C27H18Cl2N2O2, represents a racemic mixture of the corresponding R,R and S,S diastereomers. The isoxazoline ring adopts an envelope conformation with the spiro C atom deviating by 0.093 (2) Å from the rest of the ring. The six-membered keto-substituted carbocycle has a sofa conformation with the methylene C atom adjacent to the spiro center deviating by 0.289 (2) Å from the mean plane of the remaining atoms. In the crystal, molecules are linked via C—H⋯Cl interactions and C—Cl⋯O halogen bonds [2.958 (2) Å, 171.39 (7)°], which generate bifurcated R 2 1(6) ring motifs resulting in C 2 1[R 2 1(6)] chains running parallel to [010].

The title compound, C 27 H 18 Cl 2 N 2 O 2 , represents a racemic mixture of the corresponding R,R and S,S diastereomers. The isoxazoline ring adopts an envelope conformation with the spiro C atom deviating by 0.093 (2) Å from the rest of the ring. The six-membered keto-substituted carbocycle has a sofa conformation with the methylene C atom adjacent to the spiro center deviating by 0.289 (2) Å from the mean plane of the remaining atoms. In the crystal, molecules are linked via C-HÁ Á ÁCl interactions and C-ClÁ Á ÁO halogen bonds [2.958 (2) Å , 171.39 (7) ], which generate bifurcated R 2 1 (6) ring motifs resulting in C 2 1 [R 2 1 (6)] chains running parallel to [010].   Table 1 Hydrogen-bond geometry (Å , ).
The title compound C 27 H 18 Cl 2 N 2 O 2 , consists of an isoxazole ring spiro attached to acridine ring system and the phenyl rings (C22-C27) and (C16-C21). X-ray analysis confirms the molecular stereochemistry as illustrated in Fig. 1. The quinoline ring system is essentially planar with a maximum deviation of -0.049 (2) Å for C9 atom. The quinoline ring system forms a dihedral angle of 86.12 (10) ° with the chlorophenyl ring (C16-C21), which shows that they are almost orthogonal to each other. The chlorophenyl ring (C22-C27) forms a dihedral angle of 74.99 (9) ° with the quinoline ring system.
The six membered carbocyclic ring (C8-C13) adopts a sofa conformation with the deviation of C11 by -0.289 (2) Å from the mean plane formed by the remaining ring atoms. The mean plane of the six membered ring (C8-C13) forms a dihedral angle of 85.34 (11) ° with the chlorophenyl ring (C16-C21), which shows that they are almost perpendicular to each other. The oxygen atom (O1) significantly deviates from the mean plane of the ring (C8-C13) by -0.3368 (18) Å.
The mean plane of the six membered carbocyclic ring (C8-C13) forms a dihedral angle of 2.53 (8) ° with the quinoline ring system, which shows that they are almost coplanar.

Refinement
The positions of the hydrogen atoms were localized from the difference electron density maps and the distances were geometrically constrained. The H atoms bound to the C atoms, with d(C-H) = 0.93 Å and U iso (H) = 1.2U eq (C) for aromatic, d(C-H) = 0.98 Å and U iso (H) = 1.2U eq (C) for methine, d(C-H) = 0.97 Å and U iso (H) = 1.2U eq (C) for methylene groups.  The molecular structure of the title compound with the atom numbering scheme. The displacement ellipsoids are drawn at 30% probability level.

Figure 2
The crystal packing of the title compound, viewed along c-axis, showing bifurcated bonding including Cl2: C10-H10A···Cl2 i hydrogen bonds and C25 i -Cl2 i ···O2 halogen bonds, resulting into supramolecular chains C 1 2 [R 1 2 (6)] running parallel to [0 1 0] direction. The hydrogen atoms not involved in the hydrogen bonding have been excluded for clarity. 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq C1 0.0838 (