132855-24-4Relevant academic research and scientific papers
Determination of rate constants for the reaction of aryl radicals with enolate ions
Annunziata, Alfonso,Galli, Carlo,Marinelli, Manuela,Pau, Tullia
, p. 1323 - 1329 (2007/10/03)
The rate of ring closure (kC) of o-(ω-alkenyl)aryl radicals by means of an intramolecular attack of the intermediate phenyl-type radical at the tethered double bond was found to be 4.2 × 108 S-1 (for 1?) and 7.6×107 S-1 (for 8?), both being 6-exo-trig processes, and 9.6 × 109 S-1 for the 5-exo-trig process of 3?. The kC rate constant of these radicals was calibrated with respect to a known rate of H-atom abstraction (kH). The photostimulated SRN1 reactions of radical clock precursor 1 with anions PhS- and (EtO)2PO- in Me2SO at 25 °C provided the rates of addition of these nucleophiles (kY) to intermediate 1? (3.2 × 108 and 2.5 × 109 M-1 S-1, respectively). In contrast, the analogous reaction of a ketone enolate ion with precursor 1 did not take the expected SRN1 course; instead an elimination reaction was favoured. Similarly, the reactions of radical clock precursors 3 or 8 with the enolate ion failed. However, investigation of the distribution of 9-anthracenyl (11?) or 1-naphthyl (12?) radicals between two competing reactions, namely combination with a nucleophile and H abstraction from the solvent (Me2SO), was successful and eventually enabled us to find the kY values for the addition of the enolate ion to these two aryl radical intermediates (4.4 × 108 and 2.9 × 109 M-1 S-1, respectively).
Catalysis by Ferrous Ion in Nucleophilic Aromatic Substitution Reactions
Galli, Carlo,Gentili, Patrizia
, p. 1135 - 1140 (2007/10/02)
Efficient catalysis is provided by ferrous chloride in the nucleophilic aromatic substitution reaction of several aryl and heteroaryl halides with a ketone enolate ion as the nucleophile in Me2SO, to give the aryl or heteroaryl ketones in fair to good yields.The enolate ions from pinacolone, acetophenone, cyclohexanone and pentan-3-one behave successfully.A side-reaction is represented in some cases by the hydrodehalogenation of the substrate ArX, and evidence is provided for the intermediacy of both Ar(radical) and Ar(anion) species.Other significant mechanistic clues acquired include: (i) inhibition by electron and radical scavengers; (ii) entrainment of poor nucleophiles by good ones; (iii) the relative reactivity of two nucleophiles in competition experiments with Phl under Fe2+ catalysis having the same value as in the experiments under both photostimulation and spontaneous initiation.All these findings are consistent with an SRN1 mechanism of substitution where ferrous ion, in combination with the nucleophile, plays an important role in the initiation step.
Photochemical Anion-Promoted Carbon-Sulfur Cleavage Reactions of Diaryl Sulfides, Alkyl Aryl Sulfides, and Related Sulfoxides and Sulfones
Cheng, Carlos,Stock, Leon M.
, p. 2436 - 2443 (2007/10/02)
Diaryl sulfides and the related sulfoxides and sulfones react with substances such as diethyl phosphite anion, pinacolone enolate, and diphenylphosphide anion under irradiation to cleave one carbon-sulfur bond and form diethyl arylphosphonates, arylmethyl tert-butyl ketones, and aryldiphenylphosphines.Alkyl aryl sulfides and the related sulfones also experience carbon-sulfur bond cleavage under these conditions to produce arenethiols.Generally, these reactions occur in synthetically useful yields.The reactions of the anions with these sulfides, sulfoxides, and sulfones all require irradiation, but is notable that the reactions of diphenylphosphide anion occur in the visible region of the spectrum.Several lines of evidence suggest that the reaction proceeds via the familiar SRN1 pathway and that the photochemically-induced electron transfer occurs in an arene-anion complex.Thermochemical considerations dictate the cleavage direction in the anion radicals of unsymmetrical sulfides.
