The crystal structure of tricyclo[4,3,l,1<sup>3,8</sup>]undecane-4,5-dione

Braun, P. B.; Hornstra, J.; Leenhouts, J. I.

doi:10.1107/s0567740870004922

Cited by 7 publications

(3 citation statements)

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“…These bond lengths agree with the corresponding lengths in other bicyclo[2.2.2]octatriene derivatives. 12 -1S The C(8)-C(9) bonds in both isomers are 16 The C-C distances of the two propyl groups are 1.51-1.S2A. in la and 1.47-1.53A in Za, smaller than the normal C-C single bond distance.…”

Section: Preparation Of Epoxydiketonesmentioning

confidence: 87%

Synthesis and Photochemistry of syn‐ and anti‐9,10‐Epoxy‐1, 4‐dihydro‐1,4‐ethanonaphthalene‐2,3‐diones

Liao¹,

Hseu

Lin³

et al. 1991

J Chinese Chemical Soc

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The title epoxydiketones were prepared stereoselectively, direct epoxidation of 3a‐c with MCPBA produced syn isomers la‐c whereas epoxidation of 4a‐d followed by saponification of the spirolactone rings gave anti isomers 2a‐c. The stereochemistry of 1a and 2a was established by X‐ray diffraction, whereas that of the remaining epoxydiketones was determined from the correlation of visible, 1H, and 13C NMR spectral data; the differences between spectra of the corresponding syn and anti isomers are explained in terms of through‐space interaction and steric effects. Photolysis of syn isomers 1a‐c afforded the corresponding naphthalenes 8a‐c in almost quantitative yields; in contrast, irradiation of anti isomers 2a‐c gave complicated mixtures. The quantum yield of disappearance of 1a was 52 times that of 2a. Reaction mechanisms are proposed to account for the product formation. The differences in the photochemical behavior of the title syn and anti isomers are rationalized in terms of stereoelectronic effects of the epoxy rings in the syn isomers.

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Section: Preparation Of Epoxydiketonesmentioning

confidence: 87%

Synthesis and Photochemistry of syn‐ and anti‐9,10‐Epoxy‐1, 4‐dihydro‐1,4‐ethanonaphthalene‐2,3‐diones

Liao¹,

Hseu

Lin³

et al. 1991

J Chinese Chemical Soc

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“…Both Schleyer 21 and Nordlander 22 have commented that the carbonyl stretching frequency (1 698 cm-l) of 4-hOmOadamantanone (26b) is much more compatible with an eclipsed than with a staggered two-carbon bridge.% In the same paper Schleyer has presented evidence for an eclipsed bridge in the form of the solution i.r. spectrum of cis-homoadamantane-4,5-diol (27), which shows a large intramolecular hydrogen bond frequency shift (Av 89 cm-l), suggesting that this possesses a small dihedral angle and hence the preferred conformation of (26a) is itself eclipsed. However it should be realised that the gain in energy resulting from an intramolecular hydrogen bond can often be 2h ca.…”

Section: R'mentioning

confidence: 99%

Conformational studies on the bicyclo[3.3.2]decane system

Doyle¹,

Hafter²,

Parker³

1977

J. Chem. Soc., Perkin Trans. 1

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The spectral properties of a series of bicyclo[3.3.2]decane derivatives have been examined, and the occurrence, in certain cases, of abnormal 6(CH) and v(CH) i.r. absorptions attributed to a C-3, C-7 transannular methylene interaction in a twin-chair conformation. There is some evidence for a twin-chair _C boat-chair equilibrium, and data from reduction of the %one by dissolving metals reveals essentially no free energy difference between these conformers. In cases where the two-carbon bridge is constrained by a double bond, or its equivalent, such that C-I , C-9, C-1 0, and C-5 are coplanar, the preferred conformation is boat-chair as confirmed by an X-ray crystal analysis of 7.8.9.1 O-tetrahydro-6.1 O-propano-6H-cyclohepta [b]quinoxaline. When this ring system carries an ethano-bridge, the question of whether there is an eclipsed or staggered arrangement around C-9, C-I 0 is discussed in the light of U.V. and n.m.r. studies and the corresponding situation in homoadamantane, where an X-ray structure of the 1.8-bismethoxycarbonyl derivative has revealed a virtually eclipsed arrangement.

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“…& J. H.) calculated a sharpened Patterson function and started their Patterson search program (Braun, Hornstra & Leenhouts, 1969a) with the same model of 9 atoms as used for the solution of the structure of ECF (Knobler et al, 1972).…”

Section: Patterson Search By Computermentioning

confidence: 99%

The conformation of non-aromatic ring compounds. LXXVIII. The crystal and molecular structure of the 3,20-bis(ethylenedioxy) analogue of provitamin D

Braun¹,

Hornstra²,

Knobler³

et al. 1973

Acta Crystallogr Sect B

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Crystals of 3,20-bis(ethylenedioxy)-pregna-5,7-diene are monoclinic, space group P2~. The lattice constants are a= 12.22, b= 6-02, c= 15.77 A, t= 111.9 ° and Z= 2. Owing to pseudo-symmetry the solution of the structure, carried out by Patterson image-seeking methods, was difficult. The refinement, using photographic data, resulted in an R value of 13"1%. Rings A and C have distorted chair conformations, while ring B is an irregular half chair with C(I 0) above and C(9) below the planar moiety of atoms 5, 6, 7 and 8. In terms of torsion angles, the five-membered rings (the two dioxolane rings) have a halfchair conformation and ring D a form halfway between a half-chair and an envelope with C(14) as flap. IntroductionThis paper is part of structural study of steroids in the calciferol series. In a previous paper (Knobler, Romers, Braun & Hornstra, 1972) the crystal structure of an analogue of ergocalciferol (hereafter ECF) was described.The present report deals with its isomer the 3,20-bis-(ethylenedioxy) analogue of ergosterol (provitamin D2, Fig. 1) with the systematic name (IUPAC-IUBo 1969) 3,20-bis(ethylenedioxy)-pregna-5,7-diene (hereafter EPD). Except for the dioxolane rings A' and D' the atoms are numbered according to chemical convention.Because we did not succeed in obtaining proper crystals of the mother compound, ergosterol, we investigated an analogue. The omission of the side group and the introduction of dioxolane rings are, indeed, serious handicaps in the evaluation of the conformational properties of provitamin D2. Nevertheless the eludication of the structure of the chosen analogue is a useful addition to our knowledge of this class of compounds.Another steroid also having a 5,7-diene system is lumisterol. The structure of its m-bromobenzoate ester has been analysed by Hodgkin & Sayre (1952), but the authors gave no information concerning bond lengths and valency angles in the molecule. The structure of lumisterol itself is now being investigated in this laboratory. ExperimentalAs reported earlier (Knobler et al., 1972), it is very difficult to obtain proper crystals of vitamin D and its * Present address: Chemistry Department, University of California, Los Angeles, California 90024.analogues. The crystals of EPD were smaller and less stable to X-radiation than those of ECF and therefore less suitable for extended measurements by diffractometer-counter techniques. The compound crystallizes in colourless rectangular plates (001). The lattice constants (Table 1) were determined at room temperature from oscillation and zero-layer Weissenberg photographs using copper radiation. If the unit cell is assumed to contain two molecules, a density of dx= 1.23 gcm -3 is calculated, a reasonable number compared with the observed value dobs= 1.20 g cm -a obtained for the vitamin D analogue.The reflexions of a crystal with dimensions 0.05, 0.4 and 0-6 mm were recorded at room temperature with non-integrated equi-inclination Weissenberg photographs, using Cu K~ radiation and multiple film-technique. Collected we...

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The crystal structure of tricyclo[4,3,l,1^3,8]undecane-4,5-dione

Cited by 7 publications

References 1 publication

Synthesis and Photochemistry of syn‐ and anti‐9,10‐Epoxy‐1, 4‐dihydro‐1,4‐ethanonaphthalene‐2,3‐diones

Synthesis and Photochemistry of syn‐ and anti‐9,10‐Epoxy‐1, 4‐dihydro‐1,4‐ethanonaphthalene‐2,3‐diones

Conformational studies on the bicyclo[3.3.2]decane system

The conformation of non-aromatic ring compounds. LXXVIII. The crystal and molecular structure of the 3,20-bis(ethylenedioxy) analogue of provitamin D

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The crystal structure of tricyclo[4,3,l,13,8]undecane-4,5-dione

Cited by 7 publications

References 1 publication

Synthesis and Photochemistry of syn‐ and anti‐9,10‐Epoxy‐1, 4‐dihydro‐1,4‐ethanonaphthalene‐2,3‐diones

Synthesis and Photochemistry of syn‐ and anti‐9,10‐Epoxy‐1, 4‐dihydro‐1,4‐ethanonaphthalene‐2,3‐diones

Conformational studies on the bicyclo[3.3.2]decane system

The conformation of non-aromatic ring compounds. LXXVIII. The crystal and molecular structure of the 3,20-bis(ethylenedioxy) analogue of provitamin D

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The crystal structure of tricyclo[4,3,l,1^3,8]undecane-4,5-dione