CYCLOCONDENSATION OF OXALYL CHLORIDE WITH 1,2-GLYCOLS

Oxalyl chloride reacts with a wide range of acyclic 1,2-glycols 1 in the presence of triethylamine to produce 1,3-dioxolan-2-ones 3 together with 1,4-dioxane-2,3-diones 2. Ethylene glycol (1d), monosubstituted ethylene glycols 1e, j-1, and erythro-1,2-disubstituted ethylene glycols 1f, m,o provide the cyclic carbonates 3 as the minor products, while the threo-compounds 1g, i, n,p,q and pinacol (1h) afford 3 as the main products. The formation of 3 may be rationalized in terms of stereoelectronically controlled cleavage of the conjugate base 17- of the tetrahedral intermediates. The rate for the conformational change of 17- into 18- and the equilibrium constant between these conformers are proposed to be the major factors affecting the reaction pattern.