Thermal rearrangement of 2-(benzyloxy)-3-bromotropone to 2-(benzyloxy)-7-bromotropone, regarded to be the first [1, 9] sigmatropic rearrangement, was analyzed by high-pressure kinetics. ΔV≠ for the process were shown to be− 11.1 and− 10.1 cm 3 mol− 1 in isopropylbenzene and 1-hexanol, respectively. The figures confirmed the concerted nature of the rearrangement, and were similar to various [1, 5] sigmatropies of cyclopentadienes.
