STEREOSPECIFICITY IN THE GAS-PHASE - FORMATION AND CHARACTERIZATION OF CONFIGURATIONALLY STABLE CYCLOPROPYL ANIONS

We report the gas-phase preparation of cis- and trans-beta-formylcyclopropyl anion (4c and 4t) via the room temperature fluorodesilylation of their corresponding trimethylsilyl derivatives. These homoenolates do not interconvert or undergo ring-opening isomerization at 25 degrees C, and can readily be differentiated with several chemical probes. The proton affinities of both 4c and 4t have been measured, and the results are compared to ab initio computations. Cyclization to a 2-bicyclobutoxide ion (8) has been considered, and although the process is calculated to have a small activation barrier, it is found to be thermodynamically unfavorable.