26902-24-9Relevant academic research and scientific papers
Transition state analysis of model and enzymatic prenylation reactions
Lenevich, Stepan,Xu, Juhua,Hosokawa, Ayako,Cramer, Christopher J.,Distefano, Mark D.
, p. 5796 - 5797 (2008/02/04)
To obtain a transition state (TS) structure for an enzyme-catalyzed prenylation reaction, SN1 and SN2 model substitution reactions with dimethylallyl chloride were first studied. 13C Kinetic isotope effects (KIEs) for the model reactions were measured by a natural abundance NMR method and used to validate the computational methods that would be used in the subsequent determination of the enzymatic TS structure. Using a primary 13C KIE and a secondary 2H KIE measured via mass spectrometry, a TS structure for the enzyme-catalyzed reaction was computed; a density functional level of electronic structure theory using the mPW1N functional in combination with the 6-31+G(d) basis set was employed for those calculations. That structure has a C-O bond length of 1.69 A and a C-S bond length of 3.70 A. While the former bond length is similar to that for a nonenzymatic SN2 reaction, the latter is considerably (0.90 A) longer, indicating that the enzyme effects catalysis via an "exploded" TS structure. Copyright
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).
COHALOGENATION DES OLEFINES : APPLICATION A LA SYNTHESE D'ALCOOLS ALLYLIQUES
Rodriguez, J.,Dulcere, J-P,Bertrand, M.
, p. 527 - 528 (2007/10/02)
Alkenes 1 a-f are converted in three steps into the ally alcohols 4 a-f ; the cohalogenation of alkenes by NBS in alcohols constitutes the first step of this synthesis.
