2,7-Dimethyl-1,8-naphthyridine

Abstract

The asymmetric unit of the title compound, C₁₀H₁₀N₂, contains one half-mol­ecule with the two shared C atoms lying on a twofold rotation axis. The 1,8-naphthyridine is almost planar with a dihedral angle of 0.42 (3)° between the fused pyridine rings. In the crystal, mol­ecules are linked into infinite chains along the c axis by inter­molecular C—H⋯N hydrogen bonds, generating R ₂ ²(8) ring motifs. In addition, the crystal structure is further stabilized by C—H⋯π inter­actions.

Related literature

For applications of naphthyridines, see: Badawneh et al. (2001 ▶); Hawes et al. (1977 ▶); Gorecki & Hawes (1977 ▶). For mol­ecular recognition chemistry of naphthyridines, see: Goswami & Mukherjee (1997 ▶); Goswami et al. (2001 ▶, 2005 ▶). For the preparation of 2,7-dimethyl-[1,8]naphthyridine, see: Chandler et al. (1982 ▶). For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 ▶).

Experimental

Crystal data

• C₁₀H₁₀N₂

• M _r = 158.20

• Orthorhombic,

• a = 13.3977 (2) Å

• b = 19.3492 (4) Å

• c = 6.3089 (1) Å

• V = 1635.49 (5) ų

• Z = 8

• Mo Kα radiation

• μ = 0.08 mm⁻¹

• T = 100 K

• 0.57 × 0.41 × 0.24 mm

Data collection

• Bruker SMART APEXII CCD area-detector diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.939, T _max = 0.981

• 15454 measured reflections

• 1153 independent reflections

• 1116 reflections with I > 2σ(I)

• R _int = 0.024

Refinement

• R[F ² > 2σ(F ²)] = 0.034

• wR(F ²) = 0.098

• S = 1.09

• 1153 reflections

• 57 parameters

• 1 restraint

• H-atom parameters constrained

• Δρ_max = 0.51 e Å⁻³

• Δρ_min = −0.25 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: SAINT (Bruker, 2005 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ▶).

Supplementary Material

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C3—H3A⋯N1i	0.93	2.56	3.4889 (9)	175
C6—H6C⋯Cg1ii	0.96	2.78	3.5742 (8)	140
C6—H6C⋯Cg2iii	0.96	2.78	3.5742 (8)	140

Symmetry codes: (i) ; (ii) ; (iii) . Cg1 and Cg2 are the centroids of the N1/C1–C5 and C1–C2/C3A–C5A/N1A rings, respectively.

supplementary crystallographic information

Comment

Due to their wide applications in medicine, naphthyridines are one of the most useful group of compounds. They are used as antihypertensives, antitumor agents, immunostimulants and herbicide safeners (Badawneh et al., 2001; Hawes et al., 1977; Gorecki et al., 1977). Naphthyridines are also used as a key molecule in molecular recognition chemistry (Goswami & Mukherjee, 1997; Goswami et al., 2005; 2001; Sheldrick, 2008). We report here the single crystal X-ray structure.

In the title compound (I), (Fig. 1), the C1 and C2 atoms are lying on twofold rotation axis [symmetry code: -x, -y, z]. The dihedral angle between the two pyridine rings is equal to 0.42 (3)° indicating that the 1,8-naphthyridine is almost planar. The molecules are linked together into infinite chains by the intermolecular C3—H3A···N1 hydrogen bonds along the c axis (Fig. 2) generating R₂²(8) ring motifs (Bernstein et al., 1995). The crystal structure is further stabilized by the C—H···π interactions (Table 1).

Experimental

2,7-dimethyl-[1,8]naphthyridine was prepared according to the literature procedure (Chandler et al., 1982). In a sample bottle, 10 mg of compound was taken and dissolved in CHCl₃ and by slow evaporation the crystals are formed as colorless blocks.

Refinement

All hydrogen atoms were positioned geometrically with a riding model approximation with C—H = 0.93-0.96 Å and U_iso(H) = 1.2 U_eq(C). The rotating-group model was applied for the methyl groups. As there are not enough anomalous dispersion to determine the absolute structure, 923 Friedel pairs were merged before the final refinement.

Figures

Fig. 1.

The molecular structure of the title compound with atom labels and 50% probability ellipsoids for non-H atoms. Symmetry code: (i) -x, -y, z.

Fig. 2.

The crystal packing of (I), viewed down the a axis, showing the molecules are linked along the c axis. Intermolecular hydrogen bonds are shown in as dashed lines.

Crystal data

C10H10N2	F(000) = 672
Mr = 158.20	Dx = 1.285 Mg m−3
Orthorhombic, Fdd2	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: F 2 -2d	Cell parameters from 9922 reflections
a = 13.3977 (2) Å	θ = 3.0–40.6°
b = 19.3492 (4) Å	µ = 0.08 mm−1
c = 6.3089 (1) Å	T = 100 K
V = 1635.49 (5) Å3	Block, colourless
Z = 8	0.57 × 0.41 × 0.24 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer	1153 independent reflections
Radiation source: fine-focus sealed tube	1116 reflections with I > 2σ(I)
graphite	Rint = 0.024
φ and ω scans	θmax = 37.5°, θmin = 3.7°
Absorption correction: multi-scan (SADABS; Bruker, 2005)	h = −21→22
Tmin = 0.939, Tmax = 0.981	k = −32→31
15454 measured reflections	l = −10→10

Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.034	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.098	H-atom parameters constrained
S = 1.09	w = 1/[σ2(Fo2) + (0.0689P)2 + 0.3523P] where P = (Fo2 + 2Fc2)/3
1153 reflections	(Δ/σ)max < 0.001
57 parameters	Δρmax = 0.51 e Å−3
1 restraint	Δρmin = −0.25 e Å−3

Special details

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

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

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2sigma(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 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 (Ų)

	x	y	z	Uiso*/Ueq
N1	0.01020 (4)	0.05928 (3)	0.32666 (9)	0.01333 (14)
C1	0.0000	0.0000	0.44228 (13)	0.01141 (18)
C2	0.0000	0.0000	0.66711 (15)	0.01275 (18)
C3	0.01175 (6)	0.06389 (4)	0.77384 (11)	0.01521 (15)
H3A	0.0129	0.0658	0.9211	0.018*
C4	0.02138 (6)	0.12274 (4)	0.65545 (14)	0.01597 (16)
H4A	0.0289	0.1653	0.7218	0.019*
C5	0.01984 (5)	0.11846 (4)	0.42997 (11)	0.01352 (15)
C6	0.02718 (6)	0.18360 (4)	0.30155 (15)	0.01878 (15)
H6A	0.0381	0.1721	0.1554	0.028*
H6B	0.0819	0.2110	0.3525	0.028*
H6C	−0.0338	0.2094	0.3147	0.028*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
N1	0.0165 (3)	0.0124 (3)	0.0111 (3)	−0.00003 (19)	−0.00022 (18)	0.00128 (16)
C1	0.0132 (4)	0.0123 (4)	0.0087 (4)	0.0005 (3)	0.000	0.000
C2	0.0148 (4)	0.0138 (4)	0.0096 (4)	−0.0002 (3)	0.000	0.000
C3	0.0189 (3)	0.0159 (3)	0.0108 (3)	−0.0010 (2)	0.00012 (19)	−0.0019 (2)
C4	0.0196 (4)	0.0138 (3)	0.0144 (3)	−0.0006 (2)	0.0004 (2)	−0.0025 (2)
C5	0.0150 (3)	0.0124 (3)	0.0131 (3)	0.0001 (2)	−0.0002 (2)	0.0010 (2)
C6	0.0229 (3)	0.0137 (3)	0.0197 (3)	−0.0013 (2)	−0.0009 (3)	0.0038 (2)

Geometric parameters (Å, °)

N1—C5	1.3238 (8)	C3—H3A	0.9300
N1—C1	1.3662 (7)	C4—C5	1.4251 (11)
C1—N1i	1.3662 (7)	C4—H4A	0.9300
C1—C2	1.4184 (13)	C5—C6	1.5017 (10)
C2—C3i	1.4165 (9)	C6—H6A	0.9600
C2—C3	1.4165 (9)	C6—H6B	0.9600
C3—C4	1.3678 (10)	C6—H6C	0.9600
C5—N1—C1	118.23 (6)	C3—C4—H4A	120.2
N1i—C1—N1	115.46 (7)	C5—C4—H4A	120.2
N1i—C1—C2	122.27 (4)	N1—C5—C4	122.90 (7)
N1—C1—C2	122.27 (4)	N1—C5—C6	117.83 (6)
C3i—C2—C3	123.23 (9)	C4—C5—C6	119.26 (7)
C3i—C2—C1	118.39 (4)	C5—C6—H6A	109.5
C3—C2—C1	118.38 (4)	C5—C6—H6B	109.5
C4—C3—C2	118.51 (7)	H6A—C6—H6B	109.5
C4—C3—H3A	120.7	C5—C6—H6C	109.5
C2—C3—H3A	120.7	H6A—C6—H6C	109.5
C3—C4—C5	119.69 (7)	H6B—C6—H6C	109.5
C5—N1—C1—N1i	179.65 (7)	C1—C2—C3—C4	0.76 (8)
C5—N1—C1—C2	−0.35 (7)	C2—C3—C4—C5	−0.28 (11)
N1i—C1—C2—C3i	−0.46 (5)	C1—N1—C5—C4	0.88 (11)
N1—C1—C2—C3i	179.54 (5)	C1—N1—C5—C6	−177.77 (5)
N1i—C1—C2—C3	179.54 (5)	C3—C4—C5—N1	−0.57 (13)
N1—C1—C2—C3	−0.46 (5)	C3—C4—C5—C6	178.06 (6)
C3i—C2—C3—C4	−179.25 (8)

Symmetry codes: (i) −x, −y, z.

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3A···N1ii	0.93	2.56	3.4889 (9)	175
C6—H6C···Cg1iii	0.96	2.78	3.5742 (8)	140
C6—H6C···Cg2iv	0.96	2.78	3.5742 (8)	140

Symmetry codes: (ii) x, y, z+1; (iii) −x−3/4, y+3/4, z−1/4; (iv) x−1/4, −y+1/4, z−1/4.