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
Peri-selective photocycloadditions of methyl 2-pyrone-5-carboxylate with unsaturated cyclic ethers
Photosensitized cycloaddition reaction of methyl 2-pyrone-5-carboxylate (1) with 2,3-dihydrofuran gave cis- exo- and cis-endo-[2 + 2] cycloadducts across the C3-C4 double bond in 1, and a [4 + 2] cycloadduct which was different in addition-orientation from the Diels-Alder adducts. Each [2 + 2] cycloadduct was obtained by the use of sensitizers having different triplet energies. Photosensitized reactions of 1 with 3,4-dihydro-2H-pyrans afforded cis-endo-[2 + 2] cycloadducts, respectively. The photocycloaddition mechanism was also explained from the excited state of 1 calculated by means of MNDO-Cl method.
2-ピロン-5-カルボン酸メチルと不飽和化合物との熱および光付加反応
2-ピロン-5-カルボン酸メチル[1]とエチル=ビニル=エーテルまたはアクリロニトリルとの熱および光化学反応を行ない,前者の熱および光照射反応からは[4+2]環化付加物[2]を得後者の三重項光増感反応からは2種類の[4+2]環化付加物[3],[4]と1種類の[2+2]環化付加物[5]を得た.[2]と[3]はendo-8-置換 3-オキンー2-オキサピシクロ[2.2.2]オクト-5-エン-6-カルボン酸メチル,[4]は[3]のexo体,[5]はendo-7-シアノ-3-オキン-cis-2-オキサビシクロ[4.2.0]オクボト-4-エン-6-ガルボン酸メヂルである。熱反応による[2]の生成の活性化エネルギーは13.7kcal.moi-1であった。一方[3],[4],[5]は光増感反応(ET≧59kcal,mol-1)でのみ生成した。[1]とアセチレンジカルボン酸ジメチルまたはフェニルアセチレンとの光増感反応からは,それぞれ1,2,4-トリス(メトキシカルボニル)ベンゼンまたはm-フェニル安息香酸メチルを得た。これらの結果から,[1]とエチレンおよびアセチレン置換体との反応性ならびk生成物の熱安定性が明らかとなった。