Rearrangements of 3-Aryl-Substituted Cyclopropenyl Anions and the Gas-Phase Acidity of 3-(4-Methylphenyl)cyclopropene

Abstract

3-(4-Methylphenyl)-3-trimethylsilylcyclopropene and 3-(4-trifluoromethylphenyl)-3-trimethylsilylcyclopropene react with fluoride ion in the gas phase to afford 6-substituted 3-indenyl anions via a spontaneous rearrangement of their corresponding cyclopropenyl anions. These isomerizations led us to reinvestigate the reported gas-phase generation of 1,2,3-triphenylcyclopropenyl anion, and contrary to the previous study, a similar rearrangement to 1,2-diphenyl-1-indenyl anion is observed. Despite the instability of 3-aryl-3-cyclopropenyl anions, we were able to measure the acidity of 3-(4-methylphenyl)cyclopropene at the allylic position (delta H(o)acid = 398.6 +/- 1.4 kcal/mol) by the DePuy kinetic method. Ab initio calculations on the structures and energies of mono- and triaryl-substituted cyclopropenyl anions also are presented.

Fluorotrimethylsilane affinities of anionic nucleophiles: A study of fluoride-induced desilylation

“…In particular, fluoride-induced desilylation has been used to generate various cyclic [8,9] and alkenyl ions [10] in the gas phase, and overviews of the reactivity are available [7,11]. By using the reaction of fluoride with silanes, Kass and coworkers have prepared several anions for characterization, including acetamide enolate [12], cyclopropenyl derivatives [8,13], and cubyl anion [14].…”

“…By using the reaction of fluoride with silanes, Kass and coworkers have prepared several anions for characterization, including acetamide enolate [12], cyclopropenyl derivatives [8,13], and cubyl anion [14]. In addition, reaction of fluoride with disilanes causes cleavage of SiOSi bonds to produce silyl anions [15,16].…”

Cyclopropenyl Anions: Carbon Tunneling or Diradical Formation? A Contest between Jahn–Teller and Hund

“…Conversely, in the closed-shell singlet of PhCPA the HOMO is a 2 (without out-of plane distortion), and therefore it has two short and one long bond, as can be seen at the C 2 geometry in the left side of fig. 5 (interestingly, MNDO geometry optimization provides similar results compared to M06-2X, 11 but HF is qualitatively different 49 ). Due to the conjugation of the π antibonding HOMO orbital of the inner cyclopropenyl ring with the π benzenic systems, the two lower phenyls of fig.…”

Organometallic Chemistry in the Flowing Afterglow: A Review

“…DePuy, Bierbaum, and co-workers reported the reactions of organosilanes with various anions in 1980 − The presumed intermediacy of pentacoordinate silicon anions (siliconates hereafter) in such reactions stimulated a number of exploratory studies. These and the large number of other FA studies of metal-containing species are the basis of this review.…”

“…24 Their discovery that fluoride ion and certain organosilanes yield gas-phase carbanions has led to the preparation of a number of interesting gas-phase carbanions (vide infra). [24][25][26][27][28][29][30] The presumed intermediacy of pentacoordinate silicon anions (siliconates hereafter) in such reactions stimulated a number of exploratory studies. These and the large number of other FA studies of metal-containing species are the basis of this review.…”