Ethyl 2-amino-4-(4-bromophenyl)-6-methoxy-4H-benzo[h]chromene-3-carboxylate

In the title compound, C23H20BrNO4, the pyran ring has a flattened boat conformation with the O and methine C atoms lying to one side of the plane [0.160 (5) and 0.256 (6) Å, respectively] defined by the remaining atoms. Nevertheless, the 4H-benzo[h]chromene ring system approximates a plane (r.m.s. deviation = 0.116 Å) with the bromobenzene ring almost perpendicular [dihedral angle = 83.27 (16)°] and the ester group coplanar [C—C—C—O = 3.4 (5)°]; the methoxy substituent is also coplanar [C—O—C—C = 174.5 (3)°]. In addition to an intramolecular N—H⋯O(ester carbonyl) hydrogen bond, the ester carbonyl O atom also forms an intermolecular N—H⋯O hydrogen bond with the second amine H atom, generating a zigzag supramolecular chain along the c axis in the crystal packing. The chains are linked into layers in the bc plane by N—H⋯Br hydrogen bonds, and these layers are consolidated into a three-dimensional architecture by C—H⋯π interactions.

In the title compound, C 23 H 20 BrNO 4 , the pyran ring has a flattened boat conformation with the O and methine C atoms lying to one side of the plane [0.160 (5) and 0.256 (6) Å , respectively] defined by the remaining atoms. Nevertheless, the 4H-benzo[h]chromene ring system approximates a plane (r.m.s. deviation = 0.116 Å ) with the bromobenzene ring almost perpendicular [dihedral angle = 83.27 (16) ] and the ester group coplanar [C-C-C-O = 3.4 (5) ]; the methoxy substituent is also coplanar [C-O-C-C = 174.5 (3) ]. In addition to an intramolecular N-HÁ Á ÁO(ester carbonyl) hydrogen bond, the ester carbonyl O atom also forms an intermolecular N-HÁ Á ÁO hydrogen bond with the second amine H atom, generating a zigzag supramolecular chain along the c axis in the crystal packing. The chains are linked into layers in the bc plane by N-HÁ Á ÁBr hydrogen bonds, and these layers are consolidated into a three-dimensional architecture by C-HÁ Á Á interactions.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
4H-Chromene and its derivatives are biologically interesting compounds known for their anti-microbial, anti-fungal and other pharmaceutical activities (Alvey et al., 2009;Kemnitzer et al., 2007). In continuation of on-going interest in the chemical and pharmacological properties of 4H-chromene and fused 4H-chromene derivatives (Abd-El-Aziz et al., 2004;Abd-El-Aziz et al., 2007), the crystal structure of the title compound, (I), is described herein.
The molecular structure of (I), Fig. 1, is isostructural to the recently reported 4-fluoro analogue (El-Agrody et al., 2012). The pyran ring has a flattened boat conformation with the O1 and C11 atoms lying 0.160 (5) and 0.256 (6) Å, respectively, out of the plane defined by the four remaining atoms (r.m.s. deviation = 0.0174 Å). Overall, the 4H-  Table 1. Chains are linked into layers in the bc plane by N-H···Br hydrogen bonds involving the H atom involved in the intramolecular interaction to the O2 atom, Table 1. A consequence of this interaction is that the Br1 and O2 atoms are brought into close proximity, i.e. Br1···O2 i = 3.179 (3) Å [i: -x, 1/2 + y, 3/2 -z]. The three-dimensional architecture is consolidated by C-H···π interactions, Fig. 3 and Table 1.

Experimental
A solution of 4-methoxy-1-naphthol (0.01 mol) in EtOH (30 ml) was treated with ethyl α-cyano-p-bromocinnamate (0.01 mol) and piperidine (0.5 ml). The reaction mixture was heated until complete precipitation occurred after 2 h. The solid product was collected by filtration and recrystallized from ethanol to give (I); M.pt: 438-439 K.

Refinement
The C-bound H atoms were geometrically placed (C-H = 0.93-0.98 Å) and refined as riding with U iso (H) = 1.2-1.5U eq (C). The N-bound-H atom was refined with the distance restraint N-H = 0.88±0.01 Å and free U iso .

Figure 1
The molecular structure of (I) showing the atom-labelling scheme and displacement ellipsoids at the 35% probability level.    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.