Investigation into the mechanism of lithiation of 2,3-dihydrooxepin

The NMR characterization of the trienolate product of lithiation of 2,3-dihydrooxepin with 6-lithiodihydropyran in THF is reported. The NMR spectra also support a direct ring opening upon allylic lithiation via an E2-type mechanism rather than vinylic lithiation or stepwise allylic lithiation. We also found the structure of the trienolate product of this reaction to be the Z, Z configuration.