| heal.abstract |
Crystallographic studies showed that the p-(benzenesulfonyl)phenyl substituent in 2-[p-(benzenesulfonyl)-phenyl]-2-methyl-6-methoxy-2H-pyran-3(6H)-one (5-B) and in 2-[p-(benzenesulfonyl)phenyl]-2-methyl-6-[[(methylamino)carbonyl]oxy]-2H-pyran- 3(6H)-one (4-A) has a pseudoaxial orientation while the 6-substituent is cis in 5-B and trans in 4-A both in a sofa configuration. 5-B crystallizes in space group P bca with Z = 8 and the following lattice constants: a = 14.784 (3), b = 28.713 (5), c = 8.229 (1) Å. It refined to R 1 = 0.037 with 1769 independent reflections with I > 2.5σ(I). 4-A crystallizes in space group P 1 with Z = 2 and the following lattice constants: a = 9.472 (2) Å, b = 8.181 (1) Å, c = 13.972 (2) Å, α = 97.30 (1)°, β = 95.27 (1)°, γ = 67.85 (1)°. It refined to R 1 = 0.046 with 2246 independent reflections with I > 2.0σ(I). 1H NMR J 5,6 (vicinal) and J 4,6 (allylic) coupling constants of these and related compounds are correlated, and ambiguities in the use of 1H NMR data for direct configurational assignment are clarified. A new equation of the Karplus-Garbisch type is also given which correlates the J 5,6 and J 4,6 with the dihedral angle between the vinyl and allylic hydrogen bonds. In addition, the conformational equilibria of the examined 2H-pyran-3(6H)-ones is discussed. © 1982 American Chemical Society. |
en |