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

We report the gas-phase preparation of cis- and trans-beta-formylcyclo propyl anion (4c and 4t) via the room temperature fluorodesilylation o f their corresponding trimethylsilyl derivatives. These homoenolates d o not interconvert or undergo ring-opening isomerization at 25 degrees C, and can readily be differentiated with several chemical probes. Th e proton affinities of both 4c and 4t have been measured, and the resu lts are compared to ab initio computations. Cyclization to a 2-bicyclo butoxide ion (8) has been considered, and although the process is calc ulated to have a small activation barrier, it is found to be thermodyn amically unfavorable.