Crystal structure of 4,13-dimethyl-3,7,10,14,19,22,25-heptaoxapentacyclo- [25.0.0(1,6).0(6,26).0(11,16).0(11,18)]heptacosa-4,11-diene-2,15-dione.
of conjugated enones with olefins are useful for making a cyclobutane ring system. We have previously reported on the intermolecular photocycloaddition reactions of 2-pyrones with olefins,1–3 and the intramolecular photodimerization reactions of 4,4′-polymethylenedioxy-di-2-pyrones4 to clarify the reactivity involving the study of peri-, site, and stereoselectivities. As a part of an application of the cycloaddition reactions, we have planned to synthesize a macrocyclic compound possessing two cyclobutane rings using double photocycloaddition reactions of 6,6′-dimethyl-4,4′-dimethylenediox-di-2-pyrone (1) with di(ethylene glycol) divinyl ether (2). A solution of (1) (1.39 g), (2) (1.58 g), and xanthone (0.98 g) as a sensitizer in acetonitrile (500 ml) was irradiated with a 400W high-pressure mercury lamp (>350 nm ) for 20 h under a nitrogen atmosphere. After removing the solvent, an oily residue was chromatographed by silica gel (eluent: ethyl acetate–hexane) to give a solid product (3) in 20% yield, which was recrystallized from ethyl acetate. Since the usual analytical and spectroscopic techniques do not permit the identification of two types of isomers, (3) and (4) (in Fig. 1), an X-ray diffraction study of the product was carried out to determine the structure. Data collections were performed at 93 K with graphitemonochromated Mo Kα radiation on a Rigaku RAXIS-RAPID Imaging Plate diffractometer (λ = 0.71069 Å). Lorentz and polarization corrections were applied to the intensity data. The structure was solved by direct methods using SIR 92.5 The structure was refined by a full-matrix least-squares method. The non-hydrogen atoms were refined anisotropically. Hydrogen atoms were refined isotropically. All calculations were performed using the teXsan6 crystallographic software package. Table 1 gives the crystal data and experimental conditions. Figure 2 is an ORTEP diagram of the molecule, which shows the atomic-labeling scheme. The final positional parameters are given in Table 2, and selected bond lengths and angles are listed in Table 3. 1017 ANALYTICAL SCIENCES AUGUST 2001, VOL. 17 2001 © The Japan Society for Analytical Chemistry
Site-selective photocycloadditions of 2-pyrones with electron-poor olefins and the derivation from the cycloadducts
Photosensitized cycloaddition of 4,6-dimethyl-2-pyrone (1) with methacrylonitrile (3b) afforded two types of [2+2]cycloadducts, oxabicyclo[4.2.0]octenes 4b and 6b, across the C 5 -C 6 and C 3 -C 4 double bonds in 1, respectively. Photosensitized reactions of 1 with dimethyl maleate and dimethyl cyclobutene-1,2-dicarboxylate gave [2+2]cycloadducts oxabicyclo[4.2.0]octenes 4d, oxatricyclo[4.4.0.0 7 ,10]decene 4e across the C 5 -C 6 double bond, in addition to [2+2]cycloadduct oxabicyclo[2.2.2]octene 9d or bicyclo[4.2.0]octadiene 10e. The photoreactions of methyl 2-pyrone-5-carboxylate (2) with 3b and 2-chloroacrylonitrile (3c) gave [2+2]cycloadducts oxabicyclo[2.2.2]octene 5b, 5c in addition to [2+2]cycloadducts oxabicyclo[4.2.0]octenes 11b and 11c across the C 5 -C 6 double bond in 2. The ptotocycloaddition mechanism was explained from results calculated by means of PM3-CI method. Namely, the site- and:or regio-selectivite products, 4,5,8,9 and 10 were thought to come from the same site-selective radical intermediates in the case of electron-poor olefins.
Synthesis of quasi-stationary inhomogeneous impedance body of arbitrary shape
Formulas were obtained for the reflection factors of a plane wave from the inhomogeneous impedance plane, which reflects the incident wave in the given direction. The problem of synthesis of impedance inhomogeneous rotation body was solved for an arbitrary shaped generatrix for the given scattering diagram for co- and cross polarizations. Impedance distributions were obtained in explicit form. Restrictions on the class of implementable scat- terplots were formulated.