Diols and epoxides Communication 8. Reactions of isomeric ?-chloro butanol acetates with potassium hydroxide

Abstract

1. The reactions of 4-chloro-2-butanol acetate (I) and 3-chloro-1-butanol acetate (II) with potassium hydroxide were investigated. From (I) 1,3-epoxybutane is formed in 80–85% yield, but from (II) the yield of 1,3-epoxybutane is low (about 7%), and propene (about 55%), trans-2-buten-1-ol (about 6%), and 3-buten-1-ol (about 17%) are formed. 2. The course of the transformations of a γ-chloro alkanol acetate under the action of caustic alkali is essentially determined by the structure of the compound. For a system with the chlorine atom in a primary position, the main course is the formation of the β-epoxide by the mechanism of intramolecular nucleophilic exchange. In the case of a compound with the chlorine atom in a secondary position the main course is the formation of an olefin and an oxo compound. These two main processes pass through the intermediate stage of a chloroalkoxide. 3. The two main reactions may be accompanied by bimolecular nucleophilic exchange processes—the formation of a 1,3-diol and unsaturated alcohols. In the case of γ-chloro alkanol acetates, with increase in the order of the carbon atom carrying the chlorine atom the intramolecular nucleophilic exchange reaction is displaced toward 1,4- and 1,2-elimination.