Annelated furans. XVI. The stereochemistry of tetrahydrodibenzofurans

Abstract

P.m.r, spectroscopy has been used to determine the relative stereochemistry of a number of 1,2,3,9b-tetrahydrodibenzofurans and 1,2,3,4-tetrahydrodibenzofurans. As the alicyclic component of the 1,2,3,9b-tetrahydrodibenzofuran ring system was inflexible due to the incorporation of a double bond and fused rings, these molecules were conformationally ?frozen?. In contrast the alicyclic component of the 1,2,3,4-tetrahydrodibenzofuran ring system was quite mobile and here the conformational preferences have had to be considered in the allocation of configuration.