81277-93-2Relevant articles and documents
Different Z/E-selectivity depending upon the length of the acyl side chain in the formation of 2,2′-diacyl-9,9′-bifluorenylidene
Oota, Atsushi,Imai, Toshinobu,Yamazaki, Ayumi,Oba, Toru,Karikomi, Michinori,Minabe, Masahiro
, p. 333 - 335 (2007/10/03)
We studied the formation of 2,2′-diacyl-9,9′-bifluorenylidene from 2-acyl-9-bromofluorene via the corresponding intermediate 9-bromo-9,9′-bifluorenyl. It was found that dehydrobromination of the 9-bromo-9,9′-bifluorenyl derivatives occurred through the E2 elimination sequence, suggesting that the configuration of 9-bromo-9,9′-bifluorenyl isomers determined the stereochemistry of the product. Facile isomerization of the formed 9,90-bifluorenylidenes may give the observed stereo-selectivity depending upon the length of the acyl side chain.
A Kinetic Study of the Reactions of Carbonyl Ylides Formed by the Addition of Fluorenylidene to Ketones
Wong, P. C.,Griller, D.,Scaiano, J. C.
, p. 6631 - 6635 (2007/10/02)
Fluorenylidene addds to aliphatic ketones to give carbonyl ylide intermediates.With acetone, for example, laser flash photolysis experiments showed that the rate constant for this reaction was 1 x 107 M-1 s-1 in acetonitrile solvent.The resulting carbonyl ylide had an absorption spectrum with λmax = 640 nm in the absence of quenchers underwent ring closure to the corresponding oxirane.The lifetimes, τy, for the ring closure reaction are described by the equation -log(τy/s) = (13.26 +/- 0.11) - (10.96 +/- 0.12) / θ where θ = 2.3RT kcal mol-1.The spectra of the carbonyl ylides could be quenched with rate constants of circa 107 M-1 s-1 by electron-deficient olefins or oxygen.
