Reactions of oxalyl chloride with 1,2-cycloalkanediols in the presence of triethylamine

The relationship between the product patterns and the configurations of 1,2-cycloheptane- and 1,2-cyclooetanediols 9 in (lie cyclocondensations with oxalyl chloride in the presence of triethylamine at 0 degreesC has been shown analogous to that obtained for 1,2-disubstituted acyclic ethylene glycols 1: cis- 1,2-cyclooctanediol (9f) produced the cyclic oxalate 14f as the major product, while trans-1,2-cycloheptanediol (9e) and trans- 1,2-cyclooctanediol (9g) formed the cyclic carbonates 12e, g as the major products. On the other hand, the cyclic oxalates 14a-d were formed as the major products from 1,2-cyclopentane- and 1,2-cyclohexanediols regardless of the configuration. These results can be accounted for by assuming the boat-like transition states for cyclizations of the half esters of comparatively rigid five- and six-membered diols 9a-d. The cyclic oxalates 14a,c may be directly formed through the resulting tetrahedral intermediates from cis-diols (9a, c), and the cyclic carbonates 12a, c as the minor products after ring inversion of the tetrahedral intermediates. The tetrahedral intermediates from the trans-isomers 9b,d cannot undergo ring inversion, producing no traces of the cyclic carbonates 12b,d.