7-{4-[(1,3-Benzodioxol-5-yl)methyl]piperazin-1-yl}-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid

In the title structure, C25H24FN3O5, a strong intramolecular O—H⋯O hydrogen bond is present between the carboxy group at the 3-position and the carbonyl group at the 4-position. In the crystal, molecules are held together by weak C—H⋯O, C—H⋯F and π–π [centroid–centroid distance 3.6080 (8) Å] interactions. The 1,4-dihydroquinoline ring and cyclopropyl group are not in the same plane, making an interplanar angle of 57.52 (8)°.

In the title structure, C 25 H 24 FN 3 O 5 , a strong intramolecular O-HÁ Á ÁO hydrogen bond is present between the carboxy group at the 3-position and the carbonyl group at the 4position. In the crystal, molecules are held together by weak C-HÁ Á ÁO, C-HÁ Á ÁF and -[centroid-centroid distance 3.6080 (8) Å ] interactions. The 1,4-dihydroquinoline ring and cyclopropyl group are not in the same plane, making an interplanar angle of 57.52 (8) .  (2007). For the cryogenic cooler used in the data collection, see Cosier & Glazer (1986). For hydrogen bonding, see Desiraju & Steiner (1999).
The crystal structure of the title compound is reported here. The title compound shows remarkable improvement in lipophilicity by introduction of a lipophilic 3,4-methylenedioxyl benzyl group to the N atom which is situated on the C-7 piperazine ring of ciprofloxacin.
The title molecule is shown in Fig. 1. The 1,4-dihydroquinoline ring and cyclopropyl group (C31\C32\C33) are not in the same plane and the interplanar angle between them is 57.52 (8)°. The six-membered piperazine ring adopts a chair conformation. In the title structure, there is a strong intramolecular hydrogen bond O-H···O and a weak C-H···F interaction (Table 1; Fig. 2) (Desiraju & Steiner, 1999). The intermolecular interactions that are present in the structure are weak ones exclusively: a) C-H···O hydrogen bonds (Table 1) and b) π-electron ring -π-electron ring interactions in the structure as it is indicated by the distance 3.6080 (8) Å between the respective centroids of the benzene rings C7\C8\C17\C18\C12\C9 (symmetry codes x, y, z and 1-x, 1-y, -z).

Experimental
To a stirred solution of piperonyl alcohol (0.61 g, 4 mmol) in anhydrous methylene chloride (50 ml) at 0-5°C was added phosphorus tribromide (0.5 ml, 5 mmol) dropwise over a period of 15 min. The reaction mixture was stirred for additional 30 min at the 0-5°C, washed with saturated brine, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The obtained residue was dissolved in N,N-dimethyl formamide (20 ml) and anhydrous potassium carbonate (0.83 g, 6 mmol) with ciprofloxacin hydrochloride (0.51 g, 1.4 mmol) were added to this solution. The reaction mixture was heated to 40°C and stirred at this temperature for 14 h and then diluted with methylene chloride (50 ml), washed with distilled water (50 ml), dried over anhydrous sodium sulphate and concentrated under reduced pressure. The residue was purified by column chromatography (silica gel), eluted by methylene chloride and methanol in proportion 10:1 (v/v) to yield the title compound (0.32 g, 17.2 wt. %) as transparent block-like light yellow crystals, the longest

Refinement
All the H atoms were discernible in the difference electron density map. The positional parameters of the hydrogen H3 involved in the strong hydrogen bond O-H···O (Table 1) were refined freely while its displacement parameter was constrained: U iso (H3)=1.5U eq (O3). The aryl, methine and methylene hydrogens were constrained in the riding atom approximation: C-H = 0.95, 1.0, 0.99 Å for aryl, methine and methylene H atoms, respectively, while U iso (H) = 1.2U eq (C) for aryl, methine and methylene.   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.