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The conformation of t ‐butyl 2‐methoxy‐5, 6‐dihydro‐2 H ‐pyran‐6‐carboxylates and 6,6′‐ disubstituted 2‐methoxy‐5,6‐dihydro‐2 H ‐pyran derivatives on the basis of 1 H and 13 C NMR spectra
Author(s) -
Chmielewski Marek,
Jurczak Janusz,
Zamojski Aleksander,
Adamowicz Halina
Publication year - 1982
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.1270200412
Subject(s) - chemistry , pyran , stereochemistry , chemical shift , conformational isomerism , nuclear magnetic resonance spectroscopy , carbon 13 nmr , equilibrium constant , nmr spectra database , coupling constant , spectral line , molecule , organic chemistry , physics , astronomy , particle physics
Abstract The 1 H and 13 C NMR spectra of trans ‐ and cis ‐ tert ‐butyl 2‐methoxy‐5,6‐dihydro‐2 H ‐pyran‐6‐carboxylates (1 and 2) and 6,6′‐disubstituted 2‐methoxy‐5,6‐dihydro‐2 H ‐pyrans (3‐7) have been recorded. HH and CH coupling constants are discussed in terms of the 1 H 6 ⇄ 6 H 1 conformational equilibrium. It has been found that 1 occurs exclusively in the 1 H 6 conformation, whereas its cis isomer, 2, exists in an equilibrium of both half‐chair forms. 6,6′‐Disubstituted 2‐methoxy‐5,6‐dihydro‐2 H ‐pyrans 3‐6 display spectral and conformational behaviour similar to that of 1, whereas 7 resembles 2 in this respect.