MOLECULAR-ORBITAL STUDIES OF THE INTRAMOLECULAR REACTION OF PROTONATED CIS-3,4-EPOXYPENTAN-1-OL AND TRANS-3,4-EPOXYPENTAN-1-OL

The transition structures for the intramolecular reaction of protonate d cis- and trans-3,4-epoxypentan-1-ol (13) and (16), which result in t he formation of protonated cis- and trans-2-methylfuran-3-ols (14) and (18) with inversion and retention, have been determined at the ab ini tio MP2/6-31G and hybrid density functional B3LYP/6-31G* levels of th eory. Intrinsic reaction coordinate calculations for the lower energy inversion pathways for formation of the 8-methylfuran-3-ols show that intramolecular attack occurs in concert with ring opening. The reactio n pathways are far from optimum for best orbital overlap, reflecting t he strained bicyclic nature of the transition structures.