Density functional study of the lithiation of cyclic vinyl ethers in solution

Lithiation of three cyclic vinyl ethers—2,3-dihydrofuran, 3,4-dihydro-2H-pyran, and 2,3-dihydrooxepin in ethereal solution are investigated at the density functional theory level of B3LYP/6-31++G(d,p). Several solvation models were used, including the microsolvation model, the continuum models such as the Onsager model, the polarized continuum models, and the isodensity polarized continuum model, and the mixed discrete-continuum model. Both the microsolvation and the mixed discrete-continuum model gave results consistent with experiments. Theoretical calculations also indicate that lithiation of 2,3-dihydrooxepin undergoes allylic lithiation concomitant with ring opening.