Crystal structure of 3,4-diacetyl-15,21-dioxatetracyclo-[23.4.0.02,7.06,11]nonacosa-1(29),2,4,6,8,10,25,27-octaene-14,22-dione — water (1:2), C31H32O6 · 2H2O

Abstract

Source of materialThe title compound was synthesized via Photo-Dehydro-DielsAlder (PDDA) reaction by irradition of the pentane-1,5-diyl-(3-[2-{3-oxobut-1-ynyl}phenyl)propanoate for 50 min in t-butanol (yield 29 %).The product (37 mg, 0.076 mmol) was solved in 2mlofamixture of diethylether/isopentane/ethanol (5:5:2) after isolation by column chromatography (hexane/ethyl acetate 3:2) and removing the solvent. Colourless needle-like crystals were formed by slowly vaporizing the solvent. Experimental detailsThe O3···C28 moiety is disordered over two sides with an occupation ratio of 0.5/0.5. The hydrogen atoms on the aromatic rings were located from the difference Fourier map. The other hydrogen atoms were calculated in their expected positions. All H atoms were included in the refinement as riding atoms with U iso (H) =1 .2 U eq (C). The crystal structure contains disordered water as solvate molecules. In spite of several attempts, the electronic density in this area could not be resolved satisfactorily. Therefore the contribution of the disordered solvent species was subtracted from the structure factor calculations by the SQUEEZE instruction of the program PLATON. Using that program atotal potential solvent area of 342 Å (11.8 %ofthe unit cell) and an electron count of 68 were calculated, which corresponds with about two water molecules per asymmetric unit. DiscussionThe Photo-Dehydro-Diels-Alder (PDDA) reaction has been proven as versatile method for the preparation of highly functionalized aryl-naphthalenes and binaphthyles [1][2][3][4][5][6]. In continuation of this work, we investigated the capability of the PDDA reaction for macrocyclizations. The 21-membered macrocyclic ring contains a1,5-bridged naphthalene moiety and the compound may therefore be regarded as a cyclophane [7]. Furthermore, the free rotation around the single bond connecting the naphthalene ring and the phenyl ring is disabled due to steric hindrance and, consequently, this bond is a chirality axis. The absolute configuration of the drawn molecule is R with respect to this axis. Because of the centrosymmetric space group the other enantiomer also exists in the crystal. In spite of the 1,5-bridge the naphthalene ring is only weakly distorted from planarity, which can be seen from the torsion angle C1-C9-C10-C5 being 2.8(2)°.B yc ontrast, in [2](1,5)-naphthalino[2]-(2,6)pyridinophan and 1 2,13,14,18-tetracyano-5(1,4)-benzena-1(1,5)-naphthalenacyclooctaphane the chiralic deformations of the naphthalene plane are 28.1° [8] and 11.7° [9]. As in these compounds the bond lengths of the central moiety of the naphthalene ring (C2-C9, C9-C10, C6-C10, C5-C10, C1-C9) are longer (1.416 -1 .427 Å)t han the peripheric ones (1.360 -1 .397 Å), with the exception of C3-C4 (1.431 Å), whose carbon atoms are acetylated. The phenyl ring is nearly perpendicular to the naphthalene ring. The corresponding torsion angle C10-C5-C15-C16 was found to be 96.6(3)°.

Preparation of Strained Axially Chiral (1,5)Naphthalenophanes by Photo-dehydro-Diels−Alder Reaction

“…The structure of products 10 was unambiguously proven by X-ray structure of compounds 10b and 10g (Figure , for comparison the calculated structure of 10a is also depicted) . In 10b , a [10](1,5)naphthalenophane, the naphthalene moiety is strongly distorted indicating a considerable ring strain whereas the nearly planar naphthalene moiety in the [15](1,5)naphthalenophane 10g verifies a less strained molecular skeleton.…”