[GRAPHICS] A product and time-resolved kinetic study on the reactivity of tertiary arylcarbinyloxyl radicals bearing a-cyclopropyl and a-cyclobutyl groups has been carried out. Both the 1-cyclopropyl-1-phenylethoxyl (1(.)) and alpha,alpha-dicyclopropylphenylmethoxyl (2(.)) radicals undergo beta-scission to give cyclopropyl phenyl ketone as the major or exclusive product with rate constants higher than that measured for the cumyloxyl radical. It is proposed that in the transition state for beta-scission of 1(.) and 2(.), formation of the C=O double bond is assisted by overlap with the C-C bonding orbitals of the cyclopropane ring. With tertiary arylcarbinyloxyl radicals bearing a-cyclobutyl groups such as the 1-cyclobutyl-1-phenylethoxyl (4(.)) and 1-cyclobutyl-1-phenylpropoxyl (5(.)) radicals, the fragmentation regioselectivity is essentially governed by the stability of the radical formed by P-scission. Accordingly, 4(.) undergoes exclusive C-cyclobutyl bond cleavage to give acetophenone, whereas with 5(.), competition between C-cyclobutyl and C-ethyl bond cleavage, leading to propiophenone and cyclobutylphenyl ketone in a 2:1 ratio, is observed.

Bietti, M., Gente, G., & Salamone, M. (2005). Structural effects on the beta-scission reaction of tertiary arylcarbinyloxyl radicals. The role of alpha-cyclopropyl and alpha-cyclobutyl groups. JOURNAL OF ORGANIC CHEMISTRY, 70(17), 6820-6826 [10.1021/jo050883i].

Structural effects on the beta-scission reaction of tertiary arylcarbinyloxyl radicals. The role of alpha-cyclopropyl and alpha-cyclobutyl groups

BIETTI, MASSIMO;SALAMONE, MICHELA
2005

Abstract

[GRAPHICS] A product and time-resolved kinetic study on the reactivity of tertiary arylcarbinyloxyl radicals bearing a-cyclopropyl and a-cyclobutyl groups has been carried out. Both the 1-cyclopropyl-1-phenylethoxyl (1(.)) and alpha,alpha-dicyclopropylphenylmethoxyl (2(.)) radicals undergo beta-scission to give cyclopropyl phenyl ketone as the major or exclusive product with rate constants higher than that measured for the cumyloxyl radical. It is proposed that in the transition state for beta-scission of 1(.) and 2(.), formation of the C=O double bond is assisted by overlap with the C-C bonding orbitals of the cyclopropane ring. With tertiary arylcarbinyloxyl radicals bearing a-cyclobutyl groups such as the 1-cyclobutyl-1-phenylethoxyl (4(.)) and 1-cyclobutyl-1-phenylpropoxyl (5(.)) radicals, the fragmentation regioselectivity is essentially governed by the stability of the radical formed by P-scission. Accordingly, 4(.) undergoes exclusive C-cyclobutyl bond cleavage to give acetophenone, whereas with 5(.), competition between C-cyclobutyl and C-ethyl bond cleavage, leading to propiophenone and cyclobutylphenyl ketone in a 2:1 ratio, is observed.
Pubblicato
Rilevanza internazionale
Articolo
Sì, ma tipo non specificato
Settore CHIM/06 - Chimica Organica
English
Con Impact Factor ISI
Chemical bonds; Ketones; Reaction kinetics; Acetophenone; Cyclopropane ring; Regioselectivity; Transition state; Aromatic compounds; acetophenone; cyclobutane derivative; cyclopropane derivative; radical; analytic method; article; chemical reaction; cyclopropanation; drug stability; phase transition; reaction analysis; structure analysis
Bietti, M., Gente, G., & Salamone, M. (2005). Structural effects on the beta-scission reaction of tertiary arylcarbinyloxyl radicals. The role of alpha-cyclopropyl and alpha-cyclobutyl groups. JOURNAL OF ORGANIC CHEMISTRY, 70(17), 6820-6826 [10.1021/jo050883i].
Bietti, M; Gente, G; Salamone, M
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2108/38252
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