N-(2-Bromophenyl)-1,3-selenazolo[5,4-b]pyridin-2-amine

The molecular structure of the title molecule, C12H8BrN3Se, is built up from fused selenazolo and pyridine rings, linked to a 2-bromoaniline group. In the crystal, pairs of molecules are linked by N—H⋯N hydrogen bonds into dimers, forming eight-membered ring motifs.


Comment
Since the discovery of the importance of Se as a microelement in bacteria and animals, and the function of the selenoenzyme glutathione peroxidase (GPx) as an antioxidant, the interest in organoselenium compounds has increased significantly (Garud, et al. 2007;Ling, et al. 2010;Plamen, et al. 2010Plamen, et al. ,2004. The design and synthesis of organoselenium compounds, especially Se-containing heterocycles, are of our current interest. The title molecule ( Fig.1) is built up from two fused rings, viz. selenazolo and pyridine, linked to 2-bromoaniline group. In the crystal, pairs of molecules are linked by N-H-N hydrogen bonds (H-N=2.933 Å) into dimers, forming eight-membered rings motifs.

Experimental
To a stirred solution of N-phenyllformamide (10 mmol) in toluene (100 ml) in an ice bath, Et 3 N (4.0 g, 40 mmol) and Se black powder were added. Then, phosgene (8 g of a 20% solution in toluene,) was added slowly over 30 min. An exothermic reaction took place. After complete addition, the suspension was heated under reflux for 10 h (TLC control).
The mixture was filtered and washed with several portions of toluene, and then the filtrate was concentrated and afforded the raw isoselenocyanatobenzene. Isoselenocyanatobenzene was added to a stirred solution of 2-chloropyridin -3-amine (1.28 g, 10 mmol) in 2-propanol at room temperature, and the mixture was heated to reflux for 3 h. After filtration, the precipitate was collected as a yellow solid. The impure product was dissolved in CCl 2 H 2 at room temperature. Colorless crystals suitable for X-ray analysis (90.4% yield) grew over a period of one week when the solution was exposed to the air.

Refinement
The structure was solved by direct methods and refined by least squares method on F2 using the SHELXTL program package. All atoms were refined anisotropically. Hydrogen atoms were placed at the calculated positions using a riding model with C(aromatic)-H = 0.95 Å and U iso (H) = 1.2Ueq(C), and with N-H = 0.95 Å and U iso (H) =1.5Ueq(N).  The molecular structure of the title compound in (I) showing the atom numbering Scheme. Displacement ellipsoids are drawn at the 50% probability level.

N-(2-Bromophenyl)-1,3-selenazolo[5,4-b]pyridin-2-amine
Crystal data Special details Experimental. CrysAlisPro, Agilent Technologies, Version 1.171.34.49 (release 20-01-2011 CrysAlis171 .NET) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. 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.