2-Iodo-3-methoxy-6-methylpyridine

The title compound, C7H8INO, which crystallizes with three independent molecules in the asymmetric unit, was prepared by the reaction of 3-methoxy-6-methylpyridine with KI and I2 in tetrahydrofuran solution. In the crystal structure, the three independent molecules are arranged in a similar orientation with the three polar methoxy groups aligned on one side and the three non-polar methyl groups on the other side. The three molecules, excluding methyl H atoms, are essentially planar, with r.m.s. deviations of 0.0141 (1), 0.0081 (1) and 0.0066 (2)Å. The three pyridine rings make dihedral angles of 58.09 (3) 66.64 (4) and 71.5 (3)°. The crystal structure features rather weak intermolecular C—H⋯O hydrogen bonds, which link two molecules into dimers, and short I⋯N contacts [4.046 (3) Å].

The title compound, C 7 H 8 INO, which crystallizes with three independent molecules in the asymmetric unit, was prepared by the reaction of 3-methoxy-6-methylpyridine with KI and I 2 in tetrahydrofuran solution. In the crystal structure, the three independent molecules are arranged in a similar orientation with the three polar methoxy groups aligned on one side and the three non-polar methyl groups on the other side. The three molecules, excluding methyl H atoms, are essentially planar, with r.m.s. deviations of 0.0141 (1), 0.0081 (1) and 0.0066 (2)Å . The three pyridine rings make dihedral angles of 58.09 (3) 66.64 (4) and 71.5 (3) . The crystal structure features rather weak intermolecular C-HÁ Á ÁO hydrogen bonds, which link two molecules into dimers, and short IÁ Á ÁN contacts   Table 1 Hydrogen-bond geometry (Å , ). 2-Iodo-3-methoxy-6-methylpyridine W. Guo, X. Liu, L. Li and D. Deng

Comment
As is known, the Ullmann coupling reaction is an important C-C bond formation reaction. In this reaction, the halogen derivatives of aromatic compounds have been used as its reaction substrates (Vlad & Horvath. 2002). The reaction of 3-methoxy-6-methylpyridine with KI and I 2 in the presence of NaHCO 3 leads to iodo-substitution at position 2 of the pyridine ring with similar structure to the previous compound (Bunker et al. 2009), as shown by the X-ray study of the title compound (Fig. 1).
The asymmetric unit consists of three neutral C 7 H 8 INO molecules, in which the bond lengths and angles are within normal ranges (Bunker et al. 2009;Tahir et al. 2009). In the crystal structure, the three molecules are arranged in the similar orientation with the three polar methoxy groups aligning on one side and the three non-polar methyl groups siding on the other side. The pyridine ring 1 (C1-C5/N1) forms dihedral angles of 58.09 (3)° and 66.64 (4)°, respectively, with the pyridine ring 2 (C8-C12/N2) and the pyridine ring 3 (C15-19/N3). Rings 2 and 3 form a dihedral angle of 71.5 (3)°. Furthermore, the organic molecules, excluding methyl H atoms, are essentially planar, with r.m.s. deviations of 0.0141 (1), 0.0081 (1) and 0.0066 (2) Å. There are no strong halogen···halogen interactions in the structure, the shortest intermolecular I-I distances are 4.266 (2)Å. However, intermolecular C-H···O hydrogen bonds link the molecules into dimers, in which C14-H14B is donor and O2 is acceptor (Table 1, Fig. 2). This weak contacts may be effective in the stabilization of the structure.

Experimental
To a solution of 3-methoxy-6-methylpyridine (4.00 g, 30 mmol) in THF 30 ml was added 10 ml water containing 2.69 g NaHCO 3 (32 mmol). The mixture was stirred for 30 minutes. Under ice bath, the resulting solution was added dropwise a solution of I 2 (8.12 g, 32 mmol) and KI (5.31 g, 32 mmol) in water (75 ml). The mixture was then stirred 72 h at room temperature, and treated with 15° solution of sodium thiosulfate, then filtered. The resulting white solid was rinsed with ice water, and dried under vacuum to afford 2-iodo-3-methoxy-6-methylpyridine, 6.48 g, 89.7° yield. The crystalline compound was obtained through the slow volatilization of ethyl acetate containing the title compound.

Refinement
All H atoms were positioned geometrically and treated as riding, with C-H bond lengths constrained to 0.93 Å (aromatic CH), 0.96 Å (methyl CH 3 ), and with Uĩso~(H) = 1.2U eq (C) or 1.5U eq (methyl). Fig. 1. View of (I) (three molecule in the asymmetric unit) with atom numbering scheme and 30% probability displacement ellipsoids for non-hydrogen atoms.