M. Chmielewski, J. Jurczak, A. Zamojski
Dec 1, 1982
Citations
0
Influential Citations
9
Citations
Journal
Magnetic Resonance in Chemistry
Abstract
The 1H and 13C NMR spectra of trans- and cis-tert-butyl 2-methoxy-5,6-dihydro-2H-pyran-6-carboxylates (1 and 2) and 6,6′-disubstituted 2-methoxy-5,6-dihydro-2H-pyrans (3-7) have been recorded. HH and CH coupling constants are discussed in terms of the 1H6⇄6H1 conformational equilibrium. It has been found that 1 occurs exclusively in the 1H6 conformation, whereas its cis isomer, 2, exists in an equilibrium of both half-chair forms. 6,6′-Disubstituted 2-methoxy-5,6-dihydro-2H-pyrans 3-6 display spectral and conformational behaviour similar to that of 1, whereas 7 resembles 2 in this respect.