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|Title:||1H NMR spectral study of some 4-hydroxy-2,6-diphenylpiperidines and a systematic analysis of 1H chemical shifts in some piperidines and 3,7-diazabicyclo[3.3.1]nonane derivatives|
|Abstract:||1H NMR spectra have been recorded for c(4)-hydroxy-r(2),c(6)-diphenylpiperidine 7a and its t(3)-methyl, t(3)-ethyl, t(3)-isopropyl, 3,3-dimethyl and t(3), t(5)-dimethyl derivatives 8a-12a and the corresponding axial 4-hydroxy epimers 7b-12b, at 270 MHz. Various 1H chemical shifts and coupling constants have been determined by analysis of the spectra. The vicinal coupling constants suggest that boat form may make a slight contribution to the equatorial alcohols. The Δδea value for the 5-methylene protons is less in the axial alcohol than in the corresponding equatorial alcohol and in the case of 11b this value is negative. The effects of methyl, ethyl, isopropyl and hydroxyl groups on the chemical shifts of ring protons are discussed. Analysis of the reported proton chemical shifts of 9-hydroxy-3,7-diazabicyclo [3 .3.l]nonanes 1a-4a suggests that the 3,7-diphenyl compounds should exist in boat-chair conformation.|
|Appears in Collections:||IJC-B Vol.39B(07) [July 2000]|
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