3-bromo-2,5-dihydrofuran-2-one and 4-bromo-2,5-dihydrofuran-2-one

Although 3-bromo-2,5-dihydrofuran-2-one and 4-bromo-2,5-dihydrofuran-2-one were first reported in 1894, considerable ambiguity still exists about the correct structure assignment of the two compounds. The present article give s a brief overview on the varying assignments of constitution and describes a novel method for the formation of 3-bromo-2,5-dihydrofuran-2-one. A comp arison is made of the experimental C-13 NMR chemical shifts with values pre dicted by increment calculations and experimental (1)J(C-C) coupling consta nts are given for both compounds. Secure structural assignments are now ava ilable for both isomers.