On the reactions between phosphorus pentachloride and lactones

Abstract

Reactions between PCl5 and substituted or unsubstituted beta-, gamma- and epsilon- lactones have been investigated. Although gamma- butyrolactone substituted at alpha- position with an alkyl radical has given phosphorylated products of both cyclic ethers and chlorinated carboxylic acid chlorides along with gamma- chlorobutanoic acid chloride, halogen substituted gamma-butyrolactone such as alpha-bromo-gamma-butyrolactone yielded alpha-bromo-gamma-chlorobutanoic acid chloride in similar manner with beta-propiolactone which gives beta-chloropropionic acid chloride. The nature of radicals present at gamma-position also affects the reaction products. Methyl or heptyl radicals yielded different products; in the latter case phosphorylated products were not isolated. The reaction pathway of epsilon-caprolactone with PCl5 is changed by the temperature of the reaction mixture. It reacts at 20-30 degrees C to give alpha,alpha-dichlorooxepane and epsilon-chlorohexanoic acid chloride, while a phosphorylated product was observed at 60-70 degrees C. Possible mechanisms of these reactions are discussed.