¹³C Nuclear Magnetic Resonance Studies. 47. ¹³C Spectra of some exo-Methylenecycloalkanes and -norbornanes

Abstract

. 53,589 (1975).The shielding effects of the exo-methylene group on neighboring carbons in several cycloalkanes, methylcyclohexanes, and in the norbornane ring system have been characterized by I3C n.m.r. examination of 28 compounds. The results are compared with thosefor the carbonyl group and the utility of these data for structural elucidations is discussed. The more distinctive trends exhibited by the methyl carbons in these systems are compared with those for cyclohexanes, cyclohexanones, norbornanes, and norcamphors. On acaractkrise, enexaminant les spectres r.m.n. du "C de 28 composes, les effetsde blindage du groupe exo-mithyltne sur les carbones voisins dans des cycloalkanes, des mCthylcyclohexanes et des norbornanes. On compare ces rCsultats avec ceux obtenus pour le groupement carbonyle et on discute de I'utilitt de ces donnCes pour des Clucidations de structure. On compare les tendances les plus caractCristiques des carbones des mCthyles de ces systtmes avec ceux des cyclohexanes, cyclohexanones, norbornanes et norcamphres.[Traduit par le journal]

Proton chemical shifts in NMR: Part 17. Chemical shifts in alkenes and anisotropic and steric effects of the double bond

“…25 NOE experiments were then performed. The olefinic proton at 4.717 ppm was irradiated and the bridge proton at 2.670 ppm showed an NOE.…”

Synthesis and 13C nuclear magnetic resonance spectral analysis of some diterpenoids related to the cleistanthane type hydrocarbon isolated from Amphibolisantarctica

“…&eo From 17, by a standard Wittig reaction (triphenylmethylphosphonium bromide, methyl lithium) or thioketalization followed by Raney nickel desulfurization, the desired hydrocarbons 13 and 18 were obtained. Comparison of the chemical shifts assigned to 13 and 17 shows that C-12 and C-14, in compound 13, are shielded, while C-15 is deshielded, as expected for a carbonyl to exocyclic double-bond change (11). The chemical shifts for C-9 in compounds 13, 17, and 18 are similar to those observed for the same site in 7 and 8, and are in agreement with an equatorial orientation of the side chain at C-14.…”

Correlation of ring-junction stereochemistry in A-aromatic octahydrophenanthrenes with 13C n.m.r. chemical shifts

“…The alcohols (9) and ( 17), (10) and (18), or (11) and (19) were obtained together as the C-13 epimeric pairs by hydride reduction or different Grignard reactions of the ketone (16).…”