Reactivity of 1-cyclopropene-1-lactones dependent on the substitution degree

Reaction of the α-chloro lactone 10 with KOtBu gives the butoxy lactones 21 and 22; the seven-membered derivative 11 leads to 23 as the only isolable product. Formation of the α-substitution product 21 as well as the enhanced instability of the Intermediates 12 and 13 in comparison to their methyl substituted homologues 5 and 6 show the kinetical stabilization by a methyl group at C-2. Products derived from a cyclopropeno lactone of type A could not be detected.