Ethyl 2-amino-4-(3-nitrophenyl)-4H-1-benzothieno[3,2-b]pyran-3-carboxylate

The molecule of the title compound, C20H16N2O5S, is built up by one fused five-membered and two fused six-membered rings linked to ethoxycarbonyl and 3-nitrophenyl groups. The benzothienopyran ring system is nearly planar (r.m.s deviation = 0.0392 Å) and forms a dihedral angle of 86.90 (6)° with the aromatic ring of the nitrobenzene group. In the crystal, molecules are linked by N—H⋯O hydrogen bonds and by π–π interactions between the phenyl ring and the six-membered heterocyle [intercentroid distance = 3.5819 (8) Å], forming a three-dimensional network.

The molecule of the title compound, C 20 H 16 N 2 O 5 S, is built up by one fused five-membered and two fused six-membered rings linked to ethoxycarbonyl and 3-nitrophenyl groups. The benzothienopyran ring system is nearly planar (r.m.s deviation = 0.0392 Å ) and forms a dihedral angle of 86.90 (6) with the aromatic ring of the nitrobenzene group. In the crystal, molecules are linked by N-HÁ Á ÁO hydrogen bonds and byinteractions between the phenyl ring and the six-membered heterocyle [intercentroid distance = 3.5819 (8) Å ], forming a three-dimensional network.

Comment
The Michael reaction is one of the most efficient methods for effecting carbon-carbon bond formation and has wide synthetic applications (House, 1972;Kabashima et al., 2000). This reaction and its close variants have been extensively used in organic synthesis (Jung, 1991). Generally, Michael additions are conducted in a suitable solvent in the presence of a strong base either at room or at elevated temperatures. In continuing our previous works on the preparation of hetrocyclic compounds by using condensation reactions (Boughaleb et al., 2011), we now wish to describe the behavior of ethylcyanoacetate with respect to (Z)-2-(3-nitrobenzylidene)-1-benzo[b]thiophen-3(2H)-one and derivatives in ethanol, with the presence of piperidine as a basic catalyst (Cabiddu et al., 2002;Pradhan & Asish, 2005). We have shown that cyclocondensation start with a Michael 1,4-additon, followed by intramolecular cyclization via nucleophilic addition of the hydroxyl group to the cyano group and not onto the carboxylate, to afford the tricyclic heterocycle ethyl2-amino-4-(3- The molecule of the title compound, is formed by tree fused rings linked to an ethyl-3-carboxylate nd a 3-nitrophenyl group as shown in Fig. 1. The three fused rings (S1/C1-C11/O1) are almost coplanar, with the maximum deviation from the mean plane of -0.089 (2) Å at C9, and make a dihedral angle of 86.90 (6)° with the plane through the attached nitrophenyl group.
In the crystal, molecules are linked by N-H···O hydrogen bonds and by π-π interactions in a three-dimensional network as shown in Fig. 2 and Table 1.

Experimental
In a 100 ml flask equipped with a condenser was dissolved 4 mmol of (Z)-2-(3-nitrobenzylidene)-1-benzo[b]thiophen-3(2H)-one and 5 mmol of ethyl cyanoacetate in 30 ml of ethanol. Then, 1 ml of piperidine was added, and the reaction mixture was refluxed for 6 h. Thin layer chromatography revealed the formation of a single product. The organic phase was evaporated under reduce pressure. The resulting residue was recristallized from ethanol (Yield: 68%; m.p.: 493 K).

Refinement
H atoms were located in a difference map and treated as riding with C-H = 0.93-0.97 Å, N-H = 0.86 Å, and with U iso (H) = 1.2 U eq (C, N) or U iso (H) = 1.5 U eq (C) for methyl H atoms. Two ouliers (0 0 1, 0 1 0) were omitted in the last cycles of refinement.    where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.37 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 C1  (17)