Novel 1,4-Homofragmentation via an α-Lactone

Conversion of an α,α-dichloroester to the corresponding α-keto acid was unexpectedly complicated by a novel 1,4-homofragmentation. Investigation of the kinetics of this reaction revealed a mechanism involving an α-lactone intermediate, which can lead to both the desired α-keto acid and the 1,4-homofragmentation, with the product distribution being dependent upon reaction conditions. This information allowed development of a process that affords the α-keto acid exclusively and should be generally applicable to the preparation of α-keto acids from α,α-dichloroesters or acids.