6-[(2-Chloropyridin-5-ylmethyl)(ethyl)azanyl]-4-(2-fluorophenyl)-1-methyl-5-nitro-1,2,3,4-tetrahydropyridin-2-one

In the title compound, C20H20ClFN4O3, the tetrahydropyridone ring adopts a skew boat conformation. The dihedral angle between the mean planes of the benzene and pyridine rings is 80.7 (3)°. In the crystal, weak C—H⋯O interactions are observed.


Comment
In recent years, neonicotinoid insecticide compounds have rapidly grown and become a new chemical class of insecticides because of their novel structure and mode of action (Jeschke & Nauen,2008;Kagabu & Matsuno,1997;Ohno et al., 2009;Shao et al., 2008;Tian et al., 2007;Tomizawa & Casida, 2009). We report here the synthesis and crystal structure of one of these compounds, C 20 H 20 ClFN 4 O 3 , the title compound, (I).

Experimental
In the preparation of the title compound, a solution of 2-fluorobenzaldehyde (15 mmol), Meldrum's acid (15 mmol) in ethanol (30 ml), with piperidine (0.1 mmol) used as catalyst, was added dropwise and the solution was stirred at room temperature for 2 h. Nitenpyram (2.75 g, 10 mmol) was added to the reaction mixture, heated to 65 °C for 6 h and then cooled to room temperature. The reaction mixture was concentrated under reduced pressure and treated with 20 ml of water whereby the solution was extracted three times with CH 2 Cl 2 , and the combined extracts were dried over MgSO 4 .
The organic phase was evaporated under reduced pressure and the crude product was subjected to flash chromatography on silica gel, eluting with ethyl acetate /petroleum ether to afford pure yellow crystals (yield 81%). Anal. calcd. for C 20 H 20 ClFN 4 O 3 C 57.33, H 4.80, N 13.36% found, C 57.35, H 4.81, N 13.38%.

Figure 1
The molecular structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.   (6) where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.23 e Å −3 Δρ min = −0.25 e Å −3 Special details 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.

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