N-(4,6-Dimethylpyrimidin-2-yl)-4-(oxolan-2-ylamino)benzenesulfonamide

The title compound, C16H20N4O3S, adopts an l-shaped conformation, as seen by the dihedral angle of 76.93 (7)° formed between the two aromatic rings. The most notable feature of the crystal packing is the formation of N—H⋯O and N—H⋯N hydrogen bonds that lead to supramolecular chains orientated along the b axis.

The title compound, C 16 H 20 N 4 O 3 S, adopts an l-shaped conformation, as seen by the dihedral angle of 76.93 (7) formed between the two aromatic rings. The most notable feature of the crystal packing is the formation of N-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds that lead to supramolecular chains orientated along the b axis.

Comment
The co-crystallization of active pharmaceutical ingredients is an active area of contemporary crystal engineering (Shan & Zaworotko, 2008). Sulfonamide drugs, e.g. sulfadimidine and sulfameter, attract significant interest in this regard, especially owing to their propensity to form polymorphs (Caira, 2007). They are also receiving renewed attention as selective inhibitors of carbonic anhydrase isoforms (e.g. Nishimori et al., 2009). As a continuation of studies into the phenomenon of co-crystallization (Broker & Tiekink, 2008;Broker et al., 2008), the co-crystallization of N'-(4,6-dimethyl-2pyrimidinyl)sulfanilamide (sulfadimidine) and 1,4-C 6 H 4 I 2 in THF was investigated. Colourless crystals of the title compound (I) were obtained unexpectedly; we are not aware of any precedence for this reaction. The insertion of nitrenes into the α C-H bond of cyclic ethers is known (Fructos et al., 2006) and it is suggested that adventitious I 2 in 1,4-C 6 H 4 I 2 reacts with the aryl amine to give a nitrene stabilized by the para-sulfonamide group (Kemnitz et al., 1998).
The molecule of (I), Fig. 1, is bent at the S atom, N3-S1-C7 = 107.85 (10)°, and adopts an overall `L'-conformation; the dihedral angle between the two six-membered rings is 76.93 (7)°. The five membered ring adopts an envelope configuration at the C16 atom. The crystal packing is dominated by N-H···O and N-H···N hydrogen bonding interactions, Table 1, that co-operate to form a supramolecular chain along the b axis, Fig. 2.

Refinement
Carbon-bound H-atoms were placed in calculated positions (C-H 0.95-1.00 Å) and were included in the refinement in the riding model approximation with U iso (H) set to 1.2-1.5U eq (C). The nitrogen-bound H-atoms were located in a difference Fourier map and were refined with a N-H 0.880±0.001 Å restraint, and with U iso (H) = 1.2U eq (N). Fig. 1. Molecular structure of (I) showing atom-labelling scheme and displacement ellipsoids at the 50% probability level.

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(F 2 ) is used only for calculating Rfactors(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.