Dimethyl 2-[24-acetyl-28-oxo-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-27-yl]but-2-enedioate

The title compound, C31H34N2O9, is a product of the Michael addition of the cyclic secondary amine subunit of the (bispidino)aza-14-crown-4 ether to dimethyl acetylenedicarboxylate. The molecule comprises a tricyclic system containing the aza-14-crown-3 ether macrocycle and two six-membered piperidinone rings. The aza-14-crown-3-ether ring adopts a bowl conformation with a dihedral angle between the planes of the fused benzene rings of 51.14 (5)°. The central piperidone ring has a boat conformation, whereas the terminal piperidone ring adopts a chair conformation. The dimethyl ethylenedicarboxylate fragment has a cis configuration with a dihedral angle of 56.56 (7)° between the two carboxylate groups. The crystal packing is stabilized by weak C—H⋯O hydrogen bonds.

The title compound, C 31 H 34 N 2 O 9 , is a product of the Michael addition of the cyclic secondary amine subunit of the (bispidino)aza-14-crown-4 ether to dimethyl acetylenedicarboxylate. The molecule comprises a tricyclic system containing the aza-14-crown-3 ether macrocycle and two sixmembered piperidinone rings. The aza-14-crown-3-ether ring adopts a bowl conformation with a dihedral angle between the planes of the fused benzene rings of 51.14 (5) . The central piperidone ring has a boat conformation, whereas the terminal piperidone ring adopts a chair conformation. The dimethyl ethylenedicarboxylate fragment has a cis configuration with a dihedral angle of 56.56 (7) between the two carboxylate groups. The crystal packing is stabilized by weak C-HÁ Á ÁO hydrogen bonds.
In attempts to develop the chemistry for new azacrown systems and to obtain macrocyclic ligands bringing the desirable functional groups, we studied the Michael addition of the cyclic secondary amine subunit of the (bispidino)aza-14crown-4 ether to dimethyl acetylenedicarboxylate. The expected reaction is well known (Schwan & Warkentin, 1988), but might be highly hindered in the case of (bispidino)azacrown system due to the steric reasons. We have found that the expected N-vynilation reaction of the (bispidino)azacrown ether proceeded smoothly to give an N-maleinate derivative of the azacrown system with a good yield (Fig. 1).
The dihedral angle between the planes of the benzene rings fused to the aza-14-crown-4-ether moiety is 51.14 (5)°. The central piperidone ring has a boat conformation, whereas the terminal piperidone ring adopts a chair conformation. The nitrogen N24 atom has a trigonal-planar geometry (sum of the bond angles is 360.0°), while the nitrogen N27 atom adopts a trigonal-pyramidal geometry (sum of the bond angles is 340.5°). The dimethyl ethylenedicarboxylate fragment has a cis configuration with a dihedral angle of 56.56 (7)° between the two carboxylate groups.
The molecule of I possesses four asymmetric centers at the C1, C21, C22 and C26 carbon atoms and can have potentially numerous diastereomers. The crystal of I 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 of I are bound by the weak intermolecular C-H···O hydrogen bonding interactions into three-dimensional framework (Table 1).
Experimental Dimethylacetylenedicarboxylate (0.24 g, 1.69 mmol) was added to a solution of (bispidino)aza-14-crown-4ether (0.25 g, 0.57 mmol) in chloroform (20 ml). The reaction mixture was stirred at 293 K for one day (monitoring by TLC until disappearance of the starting organic compounds spots). At the end of the reaction, the formed precipitate was separated,

Refinement
The hydrogen atoms were placed in calculated positions with C-H = 0.95-1.00Å 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.   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.