Rearrangements of 3-aryl-substituted cyclopropenyl anions and the gas-phase acidity of 3-(4-methylphenyl) cyclopropene

3-(4-Methylphenyl)-3-trimethylsilylcyclopropene and 3-(4-trifluoromethylphe nyl)-3-trimethylsilylcyclopropene react with fluoride ion in the gas phase to afford B-substituted 3-indenyl anions via a spontaneous rearrangement of their corresponding cyclopropenyl anions. These isomerizations led us to r einvestigate the reported gas-phase generation of 1,2,3-triphenylcycloprope nyl anion, and contrary to the previous study, a similar rearrangement to 1 ,2diphenyl-1-indenyl anion is observed. Despite the instability of 3-aryl-3 -cyclopropenyl anions, we were able to measure the acidity of 3-(4-methylph enyl)cyclopropene at the allylic position(DeltaH(acid)(o) = 398.6 +/- 1.4 k cal/mol) by the DePuy kinetic method. Ab initio calculations on the structu res and energies of mono- and triaryl-substituted cyclopropenyl anions also are presented.