Crystal structure of 26-(4-methylphenyl)-8,11,14,17-tetraoxa-28-azatetracyclo[22.3.1.02,7.018,23]hexacosa-2,4,6,18(23),19,21,24(1),25,27-nonaene

The title compound is the product of the Chichibabin domino reaction of 1,8-bis(2-acetylphenoxy)-3,6-dioxaoctane with 4-methylbenzaldehyde and ammonium acetate in acetic acid. It is of interest with respect to its potential anticancer activity. The compound has a bowl-like conformation comprising a fused tetracyclic system containing a 4-arylpyridine fragment, two benzene rings and an aza-17-crown-5 ether moiety.

The title compound, C 30 H 29 NO 4 , is a tetracyclic system containing a 4-arylpyridine fragment, two benzene rings and an aza-17-crown-5 ether moiety, in a bowl-like arrangement. The pyridine ring is inclined to the 4-methylphenyl ring by 26.64 (6) , and by 57.43 (6) and 56.81 (6) to the benzene rings. The benzene rings are inclined to one another by 88.32 (6) . In the crystal, molecules are linked by pairs of C-HÁ Á ÁN hydrogen bonds, forming inversion dimers with an R 2 2 (14) ring motif. The dimers are linked via a number of C-HÁ Á Á interactions, forming a three-dimensional architecture.

Chemical context
Over the last decades, there has been considerable interest in pyridino-fused azacrown ethers owing to their great theoretical and practical potential (Bradshaw et al., 1993). Among them, pyridinocrownophanes containing a benzo subunit show high effectiveness as complexating ligands in metal-ion capture and separation (Pedersen, 1988). They are also of interest as phase-transfer catalysts, as membrane ion transporting vehicles (Gokel & Murillo, 1996), as active components useful in environmental chemistry (Bradshaw & Izatt, 1997), in design technology for the construction of organic sensors (Costero et al., 2005) and as nanosized on-off switches and other molecular electronic devices (Natali & Giordani, 2012). It has also been shown that the family of pyridinoazacrown compounds can possess antibacterial (An et al., 1998) and anticancer properties (Artiemenko et al., 2002;Le et al., 2015).
Recently, we have proposed a new efficient one-step Chichibabin method for the preparation of a series of Chichibabin-type condensation of 1,8-bis(2-acetylphenoxy)-3,6-dioxaoctane with 4-methylbenzaldehyde and ammonium acetate to produce the title compound (I).
pyridinocrownophanes incorporating a 14-crown-4 ether moiety (Le et al., 2014(Le et al., , 2015Anh et al., 2008;Levov et al., 2008). During the course of our attempts to develop the chemistry of these azacrown systems and obtain macrocyclic ligands which include more extended macro-heterocycles, namely the 17-crown-5 ether moiety, we have studied the Chichibabin-type condensation of 1,8-bis(2-acetylphenoxy)-3,6-dioxaoctane with 4-methylbenzaldehyde and ammonium acetate in acetic acid. This reaction (Fig. 1) proceeds smoothly under heating of the multicomponent mixture to give the expected azacrown with reasonable yield (30%). Herein, we report on the synthesis and crystal structure of this new azacrown compound (I).

Structural commentary
The molecule of the title compound, (I), is a tetracyclic system containing a 4-arylpyridine fragment (rings A = N22/C17-C22 and B = C23-C28), two benzene rings (C = C11-C16 and D = C30-C35), and an aza-17-crown-5 ether moiety, and has a bowl-like arrangement (Fig. 2). While the dihedral angles between the benzene rings and the pyridine ring are A/D = 56.81 (6) and A/C = 57.43 (6) , the dihedral angle between the 4-methylphenyl ring (B) and the pyridine ring (A) in the 4-arylpyridine fragment is only 26.64 (6) . The distances from the center of the macrocycle cavity, defined as the centroid of 664 Molecular structure of the title compound (I), with the atom labelling. Displacement ellipsoids are drawn at the 50% probability level.

Supramolecular features
In the crystal, molecules are linked by pairs of C-HÁ Á ÁN hydrogen bonds, forming inversion dimers with an R 2 2 (14) ring motif (Table 1 and Fig. 3). The dimers are linked via a number of C-HÁ Á Á interactions, forming a three-dimensional structure (Table 1).

Synthesis and crystallization
The synthesis of the title compound (I), is illustrated in Fig. 1. Ammonium acetate (10.0 g, 130 mmol) was added to a solution of 1,8-bis(2-acetylphenoxy)-3,6-dioxaoctane (0.50 g, 1.30 mmol) and p-methylbenzaldehyde (0.155 g, 1.30 mmol) in acetic acid (10 ml). The reaction mixture was then refluxed for 45 min (monitored by TLC until disappearance of the starting diketone spot). At the end of the reaction, the reaction mixture was left to cool to room temperature, neutralized with Na 2 CO 3 and extracted with ethyl acetate. The extract was purified by column chromatography on silica gel to give colourless crystals of the title compound (I) [yield 0.18 g, 30%; m.p. 471-472 K]. IR (KBr), cm À1 : C N pyridine (1607)

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2 Database search substructure S1, and results. Table 1 Hydrogen-bond geometry (Å , ).