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13 C NMR of 4,5‐epoxy‐3‐substituted decalin and analogous Δ 4 ‐octalin derivatives: Epoxide‐ and methyl‐induced shifts
Author(s) -
Pohlit Adrian Martin,
Ferraz Helena Maria Carvalho
Publication year - 1994
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260321206
Subject(s) - chemistry , decalin , epoxide , epoxy , stereochemistry , proton nmr , carbon 13 nmr , organic chemistry , catalysis
Fully assigned 13 C NMR chemical shifts for 4,5‐epoxy‐3‐keto‐, ‐3‐hydroxy‐, and ‐3‐acetoxydecalins and ‐10‐methyldecalins, Δ 4 ‐octalins and 10‐methyl‐Δ 4 ‐octalins are reported together with epoxide‐ and methyl‐induced shifts. The 4,5α‐ and 4,5β‐epoxydecalins present epoxide γ shielding in the A ring consistent in general with the syn ‐axial hydrogen rule. The 4,5α‐ and 4,5β‐epoxy‐10‐methyldecalins present only slightly different shielding effects at γ‐carbons C‐1, C‐2, C‐7, C‐9 and C‐11. Methyl‐induced shifts in 4,5α‐ and 4,5β‐epoxy‐10‐methyldecalins are similar at all carbons to those for trans ‐ and cis ‐decalins (low temperature in the case of the latter), respectively, suggesting the predominance of the transoid and cisoid A ring conformations, respectively, in these epoxides. The methyl‐induced shifts in the A ring of octalin analogues are intermediate between those of the two epoxide configurational isomers. Epoxide γ‐ anti deshielding and γ‐ syn shielding (analogous to those in 5‐hydroxydecalins) are evident when comparison is made with 13 C shifts from analogous decalins, in contrast to the result when these effects are evaluated with data for Δ 4 ‐octalin analogues.