Dimethyl 2-[23-oxo-22,24-diphenyl-8,11,14-trioxa-25-azatetracyclo[19.3.1.02,7.015,20]pentacosa-2,4,6,15(20),16,18-hexaen-25-yl]but-2-enedioate

The title compound, C39H37NO8, is a product of the Michael addition of the cyclic secondary amine subunit of aza-14-crown-4 ether to dimethyl acetylenedicarboxylate. The piperidinone ring exhibits a distorted chair conformation and the dimethyl acetylenedicarboxylate fragment has a cis configuration with a dihedral angle of 56.61 (5)° between the two carboxylate groups. The crystal packing is stabilized by the weak C—H⋯O hydrogen bonds.

In attempts to apply this chemistry for obtaining of a macrocyclic ligand bringing the desirable functional groups, we studied the Michael addition of the cyclic secondary amine subunit of the crown ether to dimethyl acetylenedicarboxylate. The expected reaction is well known (Schwan & Warkentin, 1988), but might be highly hindered due to the steric reasons. We have found, however, that the expected N-vynilation proceeded smoothly with the formation of an Nmaleinate derivative of the azacrown system.
The title compound, I, is a product of the Michael addition of the cyclic secondary amine subunit of the aza-14-crown-4 ether to dimethyl acetylenedicarboxylate ( Figure 1). The title macromolecule includes the aza-14-crown-4-ether skeletal moiety and adopts a bowl conformation ( Figure 2). The configuration of the C7-O8-C9-C10-O11-C12-C13-O14-C15 polyether chain is t-g (-) -t-t-g (+) -t (t = trans, 180°; g = gauche, ±60°). The piperidinone ring of the bicyclic fragment have a slightly flattenned chair conformation. The dihedral angle between the planes of the benzene rings fused to the aza-14-crown-4-ether moiety is 57.14 (4)°. The phenyl rings at the C22 and C24 carbon atoms occupy the sterically favorable equatorial positions and are rotated to each other by 34.06 (6)°. The carboxylate substituents are rotated to each other by 56.61 (5)°. The volume of the internal cavity of macrocycle I is approximately equal to 66 Å 3 .
The molecule of I possesses four asymmetric centers at the C1, C21, C22 and C24 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*,24S*.
In the crystal, the molecules of I are bound to each other by weak C-H···O hydrogen bonding interactions (Table 1) into three-dimensional framework.

Experimental
Dimethyl acetylenedicarboxylate (0.14 g, 0.99 mmol) was added to a solution of bis(benzo)-(β,β′-diphenyl-γpiperidono)aza-14-crown-4 ether (0.5 g, 0.99 mmol) in chloroform (20 ml). The reaction mixture was stirred at 293 K for 3 days (monitoring by TLC until disappearance of the starting organic compounds spots). At the end of the reaction, the formed precipitate was separated, washed with cold chloroform (50 ml) and re-crystallized from ethanol to give 0.61 g of

Refinement
The 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 groups and 1.2U eq (C) for the other groups].
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.