A product and time-resolved kinetic study on the reactivity of the radical cations generated from cyclopropyl(4-methoxyphenyl)phenylmethanol (1) and cyclopropyl [bis(4-methoxyphenyl)] methanol (2) has been carried out in aqueous solution. In acidic solution, 1(center dot+) and 2(center dot+) display very low reactivities toward fragmentation, consistent with the presence of groups at Ce, (aryl and cyclopropyl) that after C-alpha-C-ss bond cleavage would produce relatively unstable carbon-centered radicals. In basic solution, 1(center dot+) and 2(center dot+) display oxygen acidity, undergoing -OH-induced deprotonation from the alpha-OH group, leading to the corresponding 1,1-diarylalkoxyl radicals 1r(center dot) and 2r(center dot), respectively, as directly observed by time resolved spectroscopy. The product distributions observed in the reactions of 1(center dot+) and 2(center dot+) under these conditions (cyclopropyl phenyl ketone, cyclopropyl(4-methoxyphenyl) ketone, and 4-methoxybenzophenone from 1(center dot+); cyclopropyl(4-methoxyphenyl) ketone and 4,4 '-dimethoxybenzophenone from 2(center dot+)) have been rationalized in terms of a water-induced competition between 0-neophyl shift and C-cyclopropyl ss-scission in the intermediate 1,1-diarylalkoxyl radicals 1r(center dot) and 2r(center dot).

Bietti, M., Fiorentini, S., Pato, I., Salamone, M. (2006). Oxygen acidity of ring methoxylated 1,1-diarylalkanol radical cations bearing alpha-cyclopropyl groups. The competition between O-neophyl shift and C-cyclopropyl beta-scission in the intermediate 1,1-diarylalkoxyl radicals. JOURNAL OF ORGANIC CHEMISTRY, 71(8), 3167-3175 [10.1021/jo0600860].

Oxygen acidity of ring methoxylated 1,1-diarylalkanol radical cations bearing alpha-cyclopropyl groups. The competition between O-neophyl shift and C-cyclopropyl beta-scission in the intermediate 1,1-diarylalkoxyl radicals

BIETTI, MASSIMO;SALAMONE, MICHELA
2006-01-01

Abstract

A product and time-resolved kinetic study on the reactivity of the radical cations generated from cyclopropyl(4-methoxyphenyl)phenylmethanol (1) and cyclopropyl [bis(4-methoxyphenyl)] methanol (2) has been carried out in aqueous solution. In acidic solution, 1(center dot+) and 2(center dot+) display very low reactivities toward fragmentation, consistent with the presence of groups at Ce, (aryl and cyclopropyl) that after C-alpha-C-ss bond cleavage would produce relatively unstable carbon-centered radicals. In basic solution, 1(center dot+) and 2(center dot+) display oxygen acidity, undergoing -OH-induced deprotonation from the alpha-OH group, leading to the corresponding 1,1-diarylalkoxyl radicals 1r(center dot) and 2r(center dot), respectively, as directly observed by time resolved spectroscopy. The product distributions observed in the reactions of 1(center dot+) and 2(center dot+) under these conditions (cyclopropyl phenyl ketone, cyclopropyl(4-methoxyphenyl) ketone, and 4-methoxybenzophenone from 1(center dot+); cyclopropyl(4-methoxyphenyl) ketone and 4,4 '-dimethoxybenzophenone from 2(center dot+)) have been rationalized in terms of a water-induced competition between 0-neophyl shift and C-cyclopropyl ss-scission in the intermediate 1,1-diarylalkoxyl radicals 1r(center dot) and 2r(center dot).
2006
Pubblicato
Rilevanza internazionale
Articolo
Sì, ma tipo non specificato
Settore CHIM/06 - CHIMICA ORGANICA
English
Con Impact Factor ISI
Acidity; Alcohols; Chemical bonds; Reaction kinetics; Spectroscopic analysis; Water; Carbon-centered radicals; Diarylalkoxyl radicals; Radical cations; Positive ions; 4 methoxybenzophenone; alkanol; benzophenone derivative; cation; cyclopropyl (4 methoxyphenyl)ketone; cyclopropyl (4 methoxyphenyl)phenylmethanol; cyclopropyl phenyl ketone; cyclopropyl[bis(4 methoxyphenyl)]methanol; ketone derivative; unclassified drug; acidity; aqueous solution; article; chemical structure; dissociation; kinetics; proton transport; reaction analysis; structure analysis
Bietti, M., Fiorentini, S., Pato, I., Salamone, M. (2006). Oxygen acidity of ring methoxylated 1,1-diarylalkanol radical cations bearing alpha-cyclopropyl groups. The competition between O-neophyl shift and C-cyclopropyl beta-scission in the intermediate 1,1-diarylalkoxyl radicals. JOURNAL OF ORGANIC CHEMISTRY, 71(8), 3167-3175 [10.1021/jo0600860].
Bietti, M; Fiorentini, S; Pato, I; Salamone, M
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/39214
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