C-13 NMR-STUDIES .82. C-13 SPECTRA OF SEVERAL 10-METHYL-CIS-DECALINS - CONFORMATIONAL PREFERENCES OF SOME CIS-DECALIN DERIVATIVES

The 13C spectra of a series of 21 cis‐decalins, 17 of which bear 10‐methyl substituents, have been recorded to examine geometrical and conformational effects on the 13C shieldings. Although the data for a few of the simpler examples have been reported, these compounds were examined to obtain results for a common medium and temperature. All of the derivatives are conformationally mobile and their spectra were examined as a function of temperature to obtain shieldings representative of the slow exchange limit. The examples include compounds which populate both available chair‐chair conformations equally, some which exhibit a preference for one of these conformations and some which exist essentially in a single conformation. The data for the latter group combined with the observed temperature dependencies and results for other decalin systems led to specific assignments for each carbon. The internal consistency of the entire body of data offers strong support for these assignments. The conformational preferences observed for a number of decalones and Δ3‐10‐methyldecalin derivatives are discussed. Copyright © 1979 Heyden & Son Ltd.