Direct synthesis of 2,5-polychloro-1,2-epoxycyclopentane-1-carboxylic acids and their alkyl esters

The treatment of 3,3,6,6-tetrachloro-1,2-cyclohexanedione with sodium hydroxide gave 2,5,5-trichloro-1,2-epoxycyclopentane-1-carboxylic acid in almost quantitative yield. 3,6,6-Trichloro-2-hydroxy-2-cyclohexen-1-one was also found to be able to undergo a similar reaction providing c-2,t-5-dichoro-1,2-epoxy-r-1-cyclopentanecarboxylic acid, whose structure was confirmed by X-ray crystallographic analysis. The reactions with alkali metal alcoholates gave the corresponding esters in fair to good yields. In contrast to the properties described for further α-chloroepoxides, the prepared compounds show remarkable stability.