N-[6-(Dibromomethyl)-2-pyridyl]-2,2-dimethylpropionamide

In the molecular structure of the title compound, C11H14Br2N2O, the dimethylpropionamide substituent is twisted slightly with respect to the pyridine ring, the interplanar angle being 12.3 (2)°. The dibromomethyl group is orientated in such a way that the two Br atoms are tilted away from the pyridine ring. In the crystal structure, molecules are associated into supramolecular chains by weak C—H⋯O interactions. The crystal is further stabilized by weak N—H⋯Br and C—H⋯N interactions.

In the molecular structure of the title compound, C 11 H 14 Br 2 N 2 O, the dimethylpropionamide substituent is twisted slightly with respect to the pyridine ring, the interplanar angle being 12.3 (2) . The dibromomethyl group is orientated in such a way that the two Br atoms are tilted away from the pyridine ring. In the crystal structure, molecules are associated into supramolecular chains by weak C-HÁ Á ÁO interactions. The crystal is further stabilized by weak N-HÁ Á ÁBr and C-HÁ Á ÁN interactions.

Comment
Bromomethyl aromatic and heteroaromatic compounds (e.g. pyridine or naphthyridine derivatives) are important substrates and they have been used as the precursors for pharmacologically active compounds. Bromide compounds have applications in the synthesis of artificial receptors for molecular recognition research (Goswami & Mukherjee, 1997;Goswami et al., 2000). We have also reported the N-bromosuccinimide reaction of various heterocycles in the absence or presence of water (Goswami et al., 2001;2004). We report here the crystal structure of the title compound which is a side-chain substituted with gem-dibromo moiety of pyridine.
In Fig. 1, the O1, N2, C6, C7 atoms lie on the same plane with the maximum deviation of 0.005 (5) Å being for atom C6. The mean plane through these atoms makes the dihedral angle of 12.3 (2)° with the mean plane through pyridine ring.
The crystal packing shows that the molecules are associated into supramolecular chains via weak C-H···O interactions (Table 1). The crystal is further stabilized by weak interactions of the type N-H···Br and C-H···N (Table 1).

Experimental
To a 100 ml round bottom flask, a mixture of compound 1 (see Fig. 3) (3 g, 0.016 mol) and azobisisobutyronitrile (AIBN) (1.28 g, 7.79 mmol) were added. Dry CCl 4 (30 ml) was added and the reaction mixture was heated to reflux for 30 min with vigorous stirring in the presence of light from a 60 W lamp. When all the materials were dissolved, N-bromosuccinimide (NBS) (2.78 g, 0.016 mol) was added slowly and reflux continued for 3 h. The reaction mixture was cooled, crushed ice added, and then extracted with CCl 4 to afford the crude product. The brown liquid was purified by column chromatography over 100-200 mesh silica gel using 3% ethylacetate in petroleum ether (330-350 K) as eluent to yield a white dense liquid of compound 2 (Fig. 3) (2.12 g, yield 50%) and a crystalline solid 3 (2.18 g, yield 40%).

Refinement
The amide-H atom was located in a difference map and refined isotropically; N-H = 0.82 (5)Å. The remaining H atoms were constrained in a riding motion approximation with d(C-H) = 0.93 Å and U iso =1.2U eq (C) for aromatic-H, d(C-H) = 0.98 Å and U iso =1.2U eq (C) for methine-H, and d(C-H) = 0.96 Å and U iso =1.5U eq (C) for methyl-H. A rotating group model was used for the methyl groups. The highest residual electron density peak was located at 0.86 Å from Br1 and the deepest hole was located at 0.86 Å from Br2. Fig. 1. The molecular structure of (I), showing 50% probability displacement ellipsoids and the atomic numbering. The intramolecular C-H···O contact is drawn as a dashed line.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. 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 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq