Nucleophilic cleavage of spiroactivated cyclopropanes.1. Kinetic and thermodynamic parameters for reaction of 6,6-dimethyl-2-phenyl-5,7-dioxaspiro[2,5]octane-4,8-dione (2) with pyridine.

Reaction of the title spiroactivated cyclopropane(2) with pyridine in acetonitrite yields a zwitterionic addition product. The reaction is reversible which provides conditions under which rates and equilibria constants can be obtained along with the derived activation and thermodynamic parameters of reaction. An extended Bronsted treatment affords a β_nuc value for the reaction of 2 with substituted pyridines.