24-Acetyl-8,11,14-trioxa-24,27-diazapentacyclo[19.5.1.122,26.02,7.015,20]octacosa-2,4,6,15(20),16,18-hexaen-28-one

The title compound, C25H28N2O5, is a product of the Petrenko–Kritchenko condensation of N-acetylpiperidone with 1,5-bis(2-formylphenoxy)-3-oxapentane and ammonium acetate. The molecule comprises a fused pentacyclic system containing an aza-14-crown-3-ether macrocycle, two piperidone and two benzene rings. The aza-14-crown-3-ether ring adopts a bowl conformation. The dihedral angle between the benzene rings fused to the aza-14-crown-4-ether unit is 70.18 (4)°. The central piperidone ring has a boat conformation, whereas the terminal piperidone ring adopts a chair conformation. The conformation of the central piperidone ring is determined by two intramolecular N—H⋯O hydrogen bonds. In the crystal, molecules are linked by weak C—H⋯O interactions into chains along [010].

The title compound, C 25 H 28 N 2 O 5 , is a product of the Petrenko-Kritchenko condensation of N-acetylpiperidone with 1,5-bis(2-formylphenoxy)-3-oxapentane and ammonium acetate. The molecule comprises a fused pentacyclic system containing an aza-14-crown-3-ether macrocycle, two piperidone and two benzene rings. The aza-14-crown-3-ether ring adopts a bowl conformation. The dihedral angle between the benzene rings fused to the aza-14-crown-4-ether unit is 70.18 (4) . The central piperidone ring has a boat conformation, whereas the terminal piperidone ring adopts a chair conformation. The conformation of the central piperidone ring is determined by two intramolecular N-HÁ Á ÁO hydrogen bonds. In the crystal, molecules are linked by weak C-HÁ Á ÁO interactions into chains along [010].

Experimental
We thank the Vietnam National University, Hanoi, (grant No. QG.11.09) for the financial support of this work.
In attempts to apply this chemistry for obtaining of a macrocyclic ligand containing N-acylsubstituted bispidine moiety, we studied the Petrenko-Kritchenko condensation of the N-acetylpiperidone with 1,5-bis(2-formylphenoxy)-3-oxapentane and ammonium acetate. The reaction have proceeded smoothly to give the expected azacrown system with a good yield (Fig. 1).
The molecule of the title compound possesses four asymmetric centers at the C1, C21, C22 and C26 carbon atoms and can have potentially numerous diastereomers. The crystal of the title compound is racemic and consists of enantiomeric pairs with the following relative configuration of the centers: rac-1R*, 21S*,22R*,26S*.
In the crystal, the molecules are bound by the weak intermolecular C-H···O hydrogen bonding interactions into the chains along [010] (Fig. 3, Table 1). The crystal packing of the chains is stacking along the a axis (Fig. 3).

Experimental
Ammonium acetate (3.0 g, 39.0 mmol) was added to a solution of 1,5-bis(2-formylphenoxy)-3-oxapentane (3.14 g, 10.0 mmol) and N-acetylpiperidone (1.41 g, 10.0 mmol) in ethanol-acetic acid mixture (30 ml 1 ml). The reaction mixture was stirred at 293 K for 3 days (monitoring by TLC until disappearance of the starting heterocyclic ketone spot). At the end of the reaction, the formed precipitate was filtered off, washed with ethanol and re-crystallized from ethanol to give 2.54

Refinement
The hydrogen atom of the amino group was localized in the difference-Fourier map and refined isotropically with fixed isotropic displacement parameters [U iso (H) = 1.2U eq (N)]. The other hydrogen atoms were placed in calculated positions with C-H = 0.95-1.00 Å and refined in the riding model with fixed isotropic displacement parameters [U iso (H) = 1.5U eq (C) for the methyl group and 1.2U eq (C) for the other groups].

Figure 1
Petrenko-Kritchenko condensation of the N-acetylpiperidone with 1,5-bis(2-formylphenoxy)-3-oxapentane and ammonium acetate.    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.