4,5-Bis(4-fluorophenyl)-5-hydroxy-3-(2-methylpropanoyl)-1-phenylpyrrolidin-2-one

The title compound, C26H23F2NO3, was synthesized by the reaction of 2-(4-fluorobenzylidene)-4-methyl-3-oxo-N-phenylpentanamide and 4-fluorobenzaldehyde. The dihedral angles between the mean plane through the pyrrolidine ring (nearly planar; maximum deviation of 0.145 Å for the C atom bearing the hydroxy group) with the phenyl and benzene rings are 37.22 (7), 51.88 (7) and 87.64 (9)°, respectively. The pyyolidine ring is near coplaner, with max offset of 0.145 A for C19 atom.\uff09 In the crystal, molecules are linked by pairs of O—H⋯O hydrogen bonds into inversion dimers, which are further assembled into chains parallel to the b axis by weak C—H⋯O hydrogen bonds.

The title compound, C 26 H 23 F 2 NO 3 , was synthesized by the reaction of 2-(4-fluorobenzylidene)-4-methyl-3-oxo-N-phenylpentanamide and 4-fluorobenzaldehyde. The dihedral angles between the mean plane through the pyrrolidine ring (nearly planar; maximum deviation of 0.145 Å for the C atom bearing the hydroxy group) with the phenyl and benzene rings are 37.22 (7), 51.88 (7) and 87.64 (9) , respectively. The pyyolidine ring is near coplaner, with max offset of 0.145 A for C19 atom.\uff09 In the crystal, molecules are linked by pairs of O-HÁ Á ÁO hydrogen bonds into inversion dimers, which are further assembled into chains parallel to the b axis by weak C-HÁ Á ÁO hydrogen bonds.
pyrrole-1-heptenoic acid}, is a selective and competitive inhibitor of the enzyme hydroxyl-methylglutaryl coenzyme-A reductase (HMG-CoA-R), which plays a key role in the biosynthesis of cholesterol. By virtue of that activity atorvastatin is useful as a hypolipidemic and hypocholesterolemic agent (Lea & McTavish, 1997). The synthesis of atorvastatin is carried out via the critical intermediate 2-[2-(4-fluorophenyl)-2-oxo-1-phenylethyl]-4-methyl-3-oxo-pentanoic acid phenylamide (Sagyam et al., 20077;Baumann et al., 1992). The process for preparing this intermediate is particularly sensitive and vulnerable to the formation of some impurities which may cause product rejection and decreased yields. We report here the crystal structure of one of these impurities.
In the title compound ( Fig. 1) bond lengths and angles are within normal ranges (Allen et al., 1987). The five atoms of the pyrrolidine ring are not coplanar, with deviations from the planarity ranging from -0.124 (2) to 0.163 (2) Å. The dihedral angles between the mean plane through the pyrrolidine ring with the C13-C18 phenyl ring and the C1-C6, C7-C12 benzene rings are 37.22 (7), 51.88 (7)° and 87.64 (9)°, respectively. In the crystal structure, the molecules are linked by intermolecular O-H···O hydrogen bonds into dinuclear units (Table 1). The dinuclear units are further assembled into one-dimensional chains along the [010] direction by C-H···O hydrogen bonds.

Experimental
A mixture of 2-(4-fluorobenzylidene)-4-methyl-3-oxo-N-phenylpentanamide (5.10 g, 16.4 mmol), ethyl hydroxyethylmethyl thiazolium bromide (0.60 g, 2.38 mmol), 4-fluorobenzaldehyde (2.16 g, 17.4 mmol) and triethylamine (1.20 g, 11.9 mmol) was heated with stirring to 338 K. The reaction mixture was allowed to stand for 24 h at this temperature. Then 2-propanol (6.0 ml) was added and the mixture was heated to about 373 K. Deionized water (6.0 ml) was dropwise added to the reaction mixture over 30 min while maintaining the temperature at 338 K. After it was gradually cooled to 273 K, a white solid was isolated on a filter and washed with 2-propanol. The solid was recrystallized from ethyl acetate/hexane (1:1 v/v) and dried under vacuum at 323 K to give the title product as a white solid (2.28 g, yield 32%). Colourless crystals were obtained by vapor diffusion of pentane into an acetone solution over a period of 5 d.

Refinement
The hydroxy H atom was found in a difference Fourier map and refined using a riding model, with the O-H = 0.84 Å and with U iso (H) = 1.5 U eq (O). All other H atoms were placed in geometrically calculated position and refined using a riding model, with C-H = 0.95-1.00 Å and U iso (H) = 1.2 U eq (C) or 1.5 U eq (C) for methyl H atoms.