Study on the bromolactonisation of alkenoic acids with (diacetoxyiodo)benzene

A study on the bromolactonisation of alkenoic acids is reported. When various pent-4-enoic acids reacted with (diacetoxyiodo)benzene (DIB) and lithium bromide in CH 3 OH at room temperature, most of the five-membered bromolactones were obtained in good to excellent yields in short times. Some had two diastereoisomers. When but-3-enoic acid and trans-hex-3-enoic acid were treated under the same conditions, only unsaturated lactones were found after workup. When hex-5-enoic acid was subjected to the same conditions, however, the desired six-membered bromolactone was not successfully separated.