Lithium–potassium superbases as key reagents for the base-catalysed isomerisation of some terpenoids

Some representative monoterpenes have been isomerised under the influence of Schlosser's lithium–potassium mixed superbases, promoting β-elimination reactions. The results are compared with those obtained with butyllithium and LDA. Different selectivities and different reaction yields are achieved as a function of the base employed. These results confirm the particular reactivity of bimetallic reagents. In this paper it is proposed that the observed selectivities might depend on the conformational features of the substrate, on the strength of the organometallic reagent, as well as on steric requirements of the elimination reaction.