Carbon-13 nuclear magnetic resonance spectra of 7-heterotetracyclo[4.1.0.02,4.03,5]heptanes. Annelation effects of aziridine, oxirane, and thiirane rings. Unusual .gamma. and .delta. substituent effects

Abstract

The 18C NMR spectra of 7-heterotetracyclo[4.1.0.02.'.08.5]heptanes and of the 7-methyl-and 7-phenyltetracyclo[4.1.0.0U.os.&]heptanea have been measured, and the three-membered-ring annelation effects were determined. The unusual deahielding found for the C-3 resonance in a cyclopropane-annelated cyclopentane derivative (bicyclo[3.1.0]hexane derivative) in the chair conformation carries an even stronger effect in the analogous aziridine-, omene-, and thiirane-annelated systems. Substituents in the 7-poeition oftetracyclo

Epoxidation of substituted norbornenes. Stereochemical aspects and accompanying intramolecular transformations

“…In fact, the vast majority of known epoxynorbornanes have exo-configuration in which the protons of the C(7)H 2 bridge are appreciably non-equivalent, one of them being arranged directly The non-equivalence of the bridging protons in the 1 H NMR spectrum as well as the unusual shielding of the C(7) atom in the 13 C NMR spectrum are the two criteria, which can be used to determine the stereochemistry of an epoxynorbornane fragment. 125,128 The exo-configuration has been confirmed by X-ray diffraction analysis. 129,130 exo-Stereoselective epoxidation has also been observed for the 7-oxa analogue of norbornene 131 and for polycyclic compounds, related to norbornene but much more complicated, such as syn-1,2,3,4,5,6,7,8-octahydro-1,4:5,8-dimethanonaphthalene 11 and its derivatives 12 and 13.…”

A Novel Synthesis of 2,3‐Dihydro‐1,3‐­methano‐1H‐indene {(Bicyclo[2.1.1]hexeno)benzene} and Analysis of Its NMR Spectra

“…This becomes apparent on comparison with the nonaromatic compounds 7 – 10 , the methylene carbon atoms of which absorb at substantially higher field: C‐2 (C‐6 in the numbering of the systematic name of 7 and 8 ) at δ = 35.7–46.0 and C‐8 at δ = 30.2–33.3. In the cases of 7 and 8 , the relatively large difference between the values of C‐2 and C‐8 is caused by γ‐ syn and γ‐ anti effects that have been observed with annulated bicyclo[2.1.1]‐17 and tricyclo[3.1.0.0 2,6 ]hexane derivatives 17,18. Furthermore, the 1 H NMR resonances of the CH 2 groups of 7 – 10 appear significantly upfield from those of 3 and 11 – 16 (see Table 1, A).…”

Synthesis of 4,5,9,10-tetradehydroadamantan-2-one

“…Recently, it has been recognized that incorporation of a bicyclo[3.1.0]hexane moiety into a rigid cage system produces a large downfield shift in C-3 of that unit if C-3 is anti to the cyclopropyl group. 16 For example, the signals for C-6 in l17 and 218 occur at 36.3 and 51.3, respectively. Moreover, such effects appear to be additive for a given skeletal framework.…”