Umlagerungen von 5‐ und 6‐Cyan‐2‐norbornyl‐Kationen

Fermann, Michael; Herpers, Ekkehard; Kirmse, Wolfgang; Neubauer, R.; Renneke, Franz-Josef; Siegfried, Rainer; Wonner, A.; Zellmer, U.

doi:10.1002/cber.19891220529

Cited by 8 publications

(3 citation statements)

References 34 publications

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“…H-5 (br m). H-6a for 2,12,13, 21-23, 29, and 30 (ddd,_/ = 6, 6, 12), for 3, 24, and 31 (ddj = 4, 17), forl4(dd J = 4, 16), for 17(ddJ = 4, 17), for25(ddd,y= 1,4,17). -6ß 2,12,13, 21-23, 29, and 30 (ddd,_/ = 2, 12, 12), for 3, 24, and 31 (dddj = 1, 3, 17), for l4(dd,y = 3, 16), for 17(ddJ = 3, 17), for25(brddJ= 3,17).…”

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confidence: 99%

“…This in turn allowed the preparation of 9-11 and 18 as described (7-9). Tosylate 5 was prepared in two steps (7) from rastevione [4] isolated from the roots olStevia serrata and Stevia rhombifolia (13).…”

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confidence: 99%

“…Minor structural modifications on chemical pathways of molecular rearrangements have been highlighted recently, in particular for bicyclic structures (1-5). We recently explored the Wagner-Meerwein rearrangement of the sesquiterpenoid rastevione [4] into moreli-9-ene-6a, 7 ß^ 1-2-[8} (6). We now report acid-catalyzed rearrangements of the longipinene derivatives 1, 9,10,16,18,19, 20, 26, and 27. Although closely related, these compounds show significant differences in reactivity during rearrangement.…”

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Molecular Rearrangements in the Longipinene Series

Román¹,

Hernández²,

Cerda-Garcı́a-Rojas³

et al. 1992

J. Nat. Prod.

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Molecular Rearrangements in the Longipinene Series

Román¹,

Hernández²,

Cerda-Garcı́a-Rojas³

et al. 1992

J. Nat. Prod.

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Rearrangements of Spirocyclobutane-Substituted 2-Norbornyl Cations

Kirmse¹,

Landscheidt²,

Siegfried³

1998

Eur. J. Org. Chem.

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2‐Norbornyl cations with spiroannellated cyclobutane rings were generated for comparison with the previously studied cyclopropane analogues. Starting with the Diels‐Alder reaction of cyclopentadiene with methylenecyclobutane, spiro‐ [bicyclo[2.2.1]heptane‐2,1′‐cyclobutan]‐6‐one (11) was prepared. The tosylhydrazone 12 of 11 was photolyzed in NaOD/D2O to give the analogous alcohol 13 with a ca. 1:1 distribution of deuterium. Ring expansion was not observed, in contrast to the cyclopropane analogue. − The tosylhydrazone 22 of spiro[bicyclo[2.2.1]heptane‐2,1′‐cyclobutan]‐3‐one (21) and the related tosylates (28, 32) rearranged, in part, to afford derivatives of spiro[bicyclo[2.2.1]heptane‐7,1′‐cyclobutane] (29, 33, 34). In both series, ring expansion of the spiroannellated cyclobutane, by exo‐3,2‐C shift, was the major reaction, giving rise to a uniquely endo‐selective tertiary cation (36). Analogously positioned cyclopropane rings remain intact, due to stabilizing interactions with the neighboring positive charge which are lacking in the cyclobutane systems. − In CDCl3 solution, the tosylate 32 produced mixtures of isomeric tosylates by way of ion pair recombination. We observed that exo → exo shifts of the counterion proceed with little scrambling of 18O whereas complete equilibration of the tosylate oxygens is attained in exo → endo shifts.

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Umlagerungen von 5,5,6,6‐Tetraalkyl‐2‐norbornyl‐Kationen

1991

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When the 6,6-dimethyl-2-norbornyl cation (9) is generated from the tosylhydrazone 5 by way of the diazonium ion 8, a ' H label is distributed equally between positions 1 and 2 of the exo-alcohol 10. The degeneracy of 9, previously derived from solvolytic studies, is thus confirmed for the deaminative route. 5,5,6,6-Tetramethyl-2-norbornanone (25) (11 and 12). Again, the distributions of 'H labels are close to 1 : 1. The angular distortions expected from repulsive interactions of the methyl groups in 11 and from cyclobutane annulation in 12 do not affect the relative energies of the bridged ions.Das intensiv bearbeitete 2-Norbornyl-Kation 'I cignet sich vorzuglich zur Untersuchung sterischer und elektronischer Effekte bei kationischen Umlagerungen'). Je nach Art der Substituenten kann die verbruckte, symmetrische Struktur 2 als energiearmste Form oder als Ubergangszustand der Wagner-Meerwein-Umlagerung

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Umlagerungen von 5‐ und 6‐Cyan‐2‐norbornyl‐Kationen

Cited by 8 publications

References 34 publications

Molecular Rearrangements in the Longipinene Series

Molecular Rearrangements in the Longipinene Series

Rearrangements of Spirocyclobutane-Substituted 2-Norbornyl Cations

Umlagerungen von 5,5,6,6‐Tetraalkyl‐2‐norbornyl‐Kationen

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