Alkenes acid-catalyzed equilibration

In Section 11-7 we explained that the acid-catalyzed dehydration of alcohols gives mixtures of alkenes in which the more stable isomers predominate. Equilibrating carbocation rearrangements, followed by El, are partly responsible for these results. However, more important for the attainment of thermodynamic equilibration is that the El process is reversible As we discussed above, alkenes can be protonated by acid to form carbocations. 

To circumvent this problem, asymmetric 1,3-dipolar cycloaddition catalyzed by a metallic Lewis acid catalyst was designed to use electron-deficient alkene as a dipolarophile that has a chelating ligand structure, such as A-acyl oxazolidinone (Figure 11.2). The incorporation of a Lewis acid was expected to be equilibrating between 1,3-dipole and dipolarophile in the reaction and the reaction rate acceleration of cycloaddition occurs only in the Lewis acid/dipolarophile complex [4]. 

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