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220 Mc/s NMR spectra and geometry of some 2-substituted 1,3-dioxanes

✍ Scribed by H.R. Buys; E.L. Eliel

Publisher
Elsevier Science
Year
1970
Tongue
French
Weight
268 KB
Volume
11
Category
Article
ISSN
0040-4039

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✦ Synopsis

The geometrical features of saturated fiveand six-membered hetero rings in terms of the ring torsional angles , obtained from X-ray or electron diffraction data, and the relation between ring geome-and various physical properties (dipole moments, spectroscopical features) have been reviewed in detail (1). It appears that most six-membered hetero rings occur in the chair conformation; however, the exact geometry is strongly dependent on the nature of the hetero atom or atoms. This feature is illustrated in Fig. 1 for l,J-dioxanes and 1,3-dithianes. .A;, ,&7S FIG-l. Ring torsional angles (from X-ray analysis (2,3)) c;]559 u5' in an equatorially 2-substituted 1,3-dioxane and -dithiane (R, = p-chlorophenyl, R2 = phenyl). However, for many heterocyclic systems no diffraction data on the unsubstituted ring are available, so the question arises whether an equatorial substituent at C2 as shown in

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