Crystal structure of 5,5′-[(4-fluorophenyl)methylene]bis[6-amino-1,3-dimethylpyrimidine-2,4(1H,3H)-dione]

In the title molecule, C19H21FN6O4, the dihedral angles between the benzene ring and essentially planar pyrimidine rings [maximum deviations of 0.036 (2) and 0.056 (2) Å] are 73.32 (7) and 63.81 (8)°. The dihedral angle between the mean planes of the pyrimidine rings is 61.43 (6)°. In the crystal, N—H⋯O hydrogen bonds link molecules, forming a two-dimensional network parallel to (001) and in combination with weak C—H⋯O hydrogen bonds, a three-dimensional network is formed. Weak C—H⋯π interactions and π–π interactions, with a centroid–centroid distance of 3.599 (2) Å are also observed.

Cg is the centroid of the C7-C12 ring.

S2. Structural commentary
Uracil derivatives represent a "privileged" structural motif in a wide variety of natural and synthetic compounds with a broad spectrum of significant biological activities (Muller et al., 1993). 6-Aminouracils are the important starting compounds for the synthesis of medicinally useful xanthines and theophyllines, which are now routinely used as a phosphodiesterase inhibitor for the treatment of asthma (Buckle et al., 1994). 6-Aminouracils are regarded as the key intermediates for the synthesis of purine-based drugs, such as penciclovir, caffeine, theophylline, and theobromine (Zhi et al., (2003); Devi & Bhuyan, 2005). In addition, pyrimidine scaffolds are reported to exhibit diverse biological and pharmaceutical activities (Ibrahim & El-Metwally, 2010;Deshmukh et al., 2009), Makarov et al., 2005. Herein, we report the synthesis and crystal structure of a new arylmethylene-bis uracil derivative, namely 5,5′-((4-fluorophenyl)methylene) bis(6-amino-1,3-dimethylpyrimidine-2,4(1H,3H)-dione) synthesized via one-pot pseudo multicomponent reaction at room temperature using iodine as inexpensive and eco-friendly catalyst.
The molecular structure of the title compound is shown in Fig. 1. The distances are in the normal ranges and correspond to those observed in a related structure (Das et al., 2009). The pyrimidine rings are essentially planar with maximum deviations of 0.036 (2) and 0.056 (2) Å for C6 and N1′, respectively. The dihedral angle between the mean plane of benzene ring [C7-C12] and pyrimidine rings-A and B are 73.32 (7) ° and 63.81 (8) ° respectively. The dihedral angle between the two pyrimidine rings is 61.43 (6) °. The planarity of the phenyl group confirms its aromatic character. From the least-squares plane calculations of the phenyl moiety, the maximum deviation observed is 0.014 (2) Å for atom C8.

S5. Synthesis and crystallization
An oven-dried screw cap test tube was charged with a magnetic stir bar, 6-amino-1,3-dimethyluracil (0.155 g, 1.0 mmol), 4-fluorobenzaldehyde (0.062 g, 0.5 mmol), iodine (0.025 g, 10 mol % as catalyst), and EtOH:H 2 O (1:1 v/v; 4 ml) in a sequential manner. The reaction mixture was then stirred vigorously at room temperature and the stirring was continued for 4 h; the progress of the reaction was monitored by TLC. On completion of the reaction, a solid mass precipitated out, which was filtered, and washed with aqueous ethanol to obtain the crude product that was purified just by recrystallization from ethanol without carrying out column chromatography (72% yield Crystals suitable for X-ray diffraction were grown by dissolving 50 mg of the title compound in 5 ml DMSO and after several days at ambient temperature colourless block-shaped crystals were formed.

S6. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1. Atoms H30, H40 attached to N15 and H50, H60 attached to N18 were located in a difference Fourier map and refined isotropically. All the remaining H atoms were geometrically fixed and allowed to ride on their parent C atoms, with C-H distances of 0.93-0.98 Å; and with U iso (H) = 1.2U eq (C), except for the methyl group where U iso (H) = 1.5U eq (C). 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.