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Carbon‐13 n.m.r. spectra of 2,3‐dimethylenebicyclo[2.2.1]heptanes and 2,3‐dimethylene‐7‐oxabicyclo[2.2.1]heptanes
Author(s) -
Quarroz Daniel,
Sonney JeanMarie,
Chollet André,
Florey André,
Vogel Pierre
Publication year - 1977
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270091102
Subject(s) - chemical shift , methylene , substituent , chemistry , methylene bridge , double bond , stereochemistry , nmr spectra database , medicinal chemistry , spectral line , organic chemistry , physics , astronomy
Abstract The 13 C n.m.r. spectra of 11 derivatives of 2,3‐dimethylenenorbornane, 1–11, of 5 derivatives of 2,3‐dimethylene‐7‐oxanorbornane, 12–16, and of 2,3,5,6‐tetramethylene‐7‐oxanorbornane (17) have been measured and the chemical shifts have been assigned. The effects of 1‐methyl, 5‐hydroxy, 5‐acetoxy, 5 ‐para ‐bromobenzenesulphonyloxy and 5‐keto substituents on the olefinic carbons of the s ‐ cis ‐butadiene group are compared with the same substituent effects reported for model compounds. Apparent linear correlations between the reciprocals of the V ← N transition energies of the butadiene chromophores and the differences of the chemical shifts ΔδC between the quaternary and methylene olefinic carbons are found for the dienes 1–3, 12–14, butadiene and 2,3‐dimethylbutadiene. The ΔδC of the olefinic carbons of the tetraene 17 also falls on the correlation line if the average of the two absorption hands at 250 and 228 nm is taken for the V ← N transition energy of this compound. The chemical shift of the carbon of the methano bridge H 2 C‐7 is almost insensitive to the presence of one or two methylene groups at C‐2,3, in contrast with the downfield shift of 10–14 ppm observed when an endocyclic double bond is introduced into the norbornane skeleton.