Carbon-13 chemical shifts in bicyclo[3.3.0]octanes

Abstract

From a detailed analysis of the carbon-13 spectral data of 52 bicyclo[3.3.0]octanes a set of substituent effects was derived from the monosubstituted compounds. Using the shift change values (AS) from this basis set, it is possible to accurately predict chemical shifts for polyfunctionalized bicyclo[3.3.0]octanes. These predictions, used in conjunction with statistical tools (IEl and R values), permit regio-and stereochemical analysis of new bicyclo[3.3.0] derivatives.

Gold‐Mediated Isomerization of ­Cyclooctyne to Ring Fused Olefinic Bicycles

“…[54,55] The X-ray structure of 4[SbF 6 ] ( Figure 2) revealed that the gold center adopts an essentially linear coordination geometry with a C (carbene) -Au-(-C≡C-centroid ) angle of 176.7°. The Au-C(carbene) and Au-(-C≡C-centroid ) distances are 2.012 (4) 6 ], they were also synthesized via independent routes using authentic free alkenes bicyclo [3.3.0]oct-1(5)-ene (2) [56,57] and cis-bicyclo-[3.3.0]oct-2-ene (3) [58] (prepared following literature procedures), and (IPr)AuSbF 6 6 ] are rotated by about 79°(average) relative to the carbene Au(N-C-N) planes whereas in 6[SbF 6 ], this angle is about 74°. The structurally authenticated alkenes adducts of (IPr)Au + show a range of such inter-planar angles from essentially coplanar to nearly perpendicular suggesting that the relative alkene orientation is determined largely by steric factors, [37] presumably arising from interaction with methyl hydrogens on the IPr ligand.…”

“…[66] and was dried using 4 Å molecular sieves (see below as well). (IPr)AuCl, [54] (IPr)AuCl 3 , [67] [(SIPr)Au(cyclooctyne)][SbF 6 ], [25] and AgNTf 2 , [68] bicyclo [3.3.0]oct-1(5)-ene, [56,57,69] and cis-bicyclo [3.3.0]oct-2-ene [58] were prepared according to reported procedures. AgSbF 6 was purchased from commercial sources and used as received.…”

Formale Totalsynthese von (±)‐Isocomen durch Anwendung der α‐Alkinon‐Cyclisierung

“…fur CI3H2,0 (194,32): C 80,35,H 11,41;gef. : C 80,24,H 11,25. 9. Reduktion des ( I mmol) 4-(N,N-Dimethylamino)pyridin [29] in 2 ml CH,CI, wurde mit 65 mg (0,282 mmol) 3,s-Dinitrobenzoyl-chlorid versetzt und 18 h bei RT.…”

“…Wie bei bevorzugter Hydrierung von der exo -Seite erwartet [24], entstand dabei hauptsachlich das 4-endo -CH,-Derivat 14 und daneben wenig 6 (Schema 4 ) . Das "C-NMR-Signal der 4-endo-standigen CH,-Gruppe von 14 ist -ubereinstimmend mit Beobachtungen anderer Autoren [25] -im Vergleich zur 4-ex0 -CH,-Gruppe von 6 nach hoherem Feld verschoben.…”

“…Wie bei bevorzugter Hydrierung von der exo -Seite erwartet [24], entstand dabei hauptsachlich das 4-endo -CH,-Derivat 14 und daneben wenig 6 (Schema 4 ) . Das "C-NMR-Signal der 4-endo-standigen CH,-Gruppe von 14 istubereinstimmend mit Beobachtungen anderer Autoren [25] im Vergleich zur 4-ex0 -CH,-Gruppe von 6 nach hoherem Feld verschoben. Eine Konfigurationszuordnung der nur in Gemischen erhaltenen Ketone 9a und 9b war zwar fur den weiteren Verlauf unserer Synthese nicht mehr notwendig, doch interessierten wir uns fur sie im Zusammenhang mit einer Interpretation sterischer Effekte im cis-Bicyclo[3.3.0]octan-System.…”