6925-23-1Relevant academic research and scientific papers
Phosphine-catalyzed stereoselective dimerizations of ketenes
Ibrahim, Ahmad A.,Wei, Pei-Hsun,Harzmann, Gero D.,Nalla, Divya,Mondal, Mukulesh,Wheeler, Kraig A.,Kerrigan, Nessan J.
, (2020/12/21)
Full details of optimisation studies of the phosphine-catalyzed ketene homodimerization reaction and the detailed development of an asymmetric variant are discussed. Studies towards the development of a phosphine-catalyzed ketene heterodimerization reaction are revealed. A discussion of possible reaction mechanisms for the dimerization reactions, supported by spectroscopic analysis of intermediates and trapping experiments, is also presented.
Mechanistic studies of the phosphine-catalyzed homodimerization of ketoketenes
Wei, Pei-Hsun,Ibrahim, Ahmad A.,Mondal, Mukulesh,Nalla, Divya,Harzmann, Gero D.,Tedeschi, Frank A.,Wheeler, Kraig A.,Kerrigan, Nessan J.
scheme or table, p. 6690 - 6694 (2011/02/24)
The mechanism of PBu3-catalyzed homodimerization of ketoketenes has been explored and compared with that of the previously reported trialkylphosphite-mediated reactions. NMR studies of the PBu3- catalyzed reaction implicated the involvement of tetravalent phosphonium intermediates. Phosphonium intermediates in the catalytic cycle were trapped through reaction with trimethylsilyl chloride and 4-chlorobenzaldehyde, and the resulting products were characterized. A method for the stoichiometric generation of phosphonium enolates was developed as a result of these studies. No evidence was obtained for the involvement of pentacovalent phosphorane intermediates in trialkylphosphine-catalyzed ketoketene homodimerization reactions, in contrast with the mechanism of the trialkylphosphite-mediated homodimerization of dimethylketene. An X-ray crystal structure analysis of methylphenylketene dimer showed that it possesses Z-geometry about the exocyclic olefin.
Cycloaddition Reactions of Heterocumulenes, XXVIII. - A 1,6-Dipole Stabilized by No-Bond Resonance. - Molecular Structure and Reactivity
Schaumann, Ernst,Kausch, Erwin,Klaska, Karl-Heinz,Klaska, Rolf,Eck, Joachim
, p. 405 - 410 (2007/10/02)
The X-ray structural investigation of the 1,6-dipole 1 reveals an intramolecular S-N contact of 236 pm, which indicates stabilization by no-bond resonance.In reactions with the heterocumulenes 2-5, the thiazoline ring of 1 is opened to give the heterocycles 7a-f, 8e.The reaction of bis(trimethylsilyl)thioketene (6) takes a deviating pathway: the primary adduct 15 gives a sigmatropic 1,3 shift of the dimethylamino group to yield product 16b.This constitution is derived from an X-ray structural study of the degradation product 17.
