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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-2H-pyran derivatives on the basis of 1H and 13 C NMR spectra

✍ Scribed by Marek Chmielewski; Janusz Jurczak; Aleksander Zamojski; Halina Adamowicz

Publisher
John Wiley and Sons
Year
1982
Tongue
English
Weight
474 KB
Volume
20
Category
Article
ISSN
0749-1581

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✦ Synopsis

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.

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