Anomeric Effect Involving Carboxyl and Ethynyl Group in Sulfur-Containing Heterocycles

Abstract

Abstract Normal anomeric effect is found in 1,3-dithiane-2-carboxylic acid, 1,3,5-trithiane-2-carboxylic acid, and their esters, in contrast to a report that oxane-2-carboxylic acid derivatives exhibit reverse anomeric effect. The results are interpreted from the difference in bond lengths between oxanes and polythianes which affects the extent of 1,3-diaxial interaction. The anomeric effect is found to be larger in 1,3-dithianes than in 1,3,5-trithianes. The differences is discussed on the ground of the energy levels of available electrons. Phenylethynyl derivatives also show small but definite anomeric effect.