A steady-state and laser flash photolysis (LFP) study of the TPPBF 4-photosensitized oxidation of ring-methoxylated benzyl alcohols has been carried out. Direct evidence on the involvement of intermediate benzyl alcohol radical cations and benzylic cations in these reactions has been provided through LFP experiments. The reactions lead to the formation of products (benzaldehydes, dibenzyl ethers, and diphenylmethanes) whose amounts and distributions are influenced by the number and relative position of the methoxy substituents. This behavior has been rationalized in terms of the interplay between the stabilities of benzyl alcohol radical cations and benzyl cations involved in these processes. A general mechanism for the TPPBF 4-photosensitized reactions of ring-methoxylated benzyl alcohols has been proposed, where the a-OH group of the parent substrate acts as the deprotonating base promoting α-C-H deprotonation of the benzyl alcohol radical cation (formed after electron transfer from the benzyl alcohol to TPP*) to give a benzyl radical and a protonated benzyl alcohol, precursor of the benzylic cation. This hypothesis is in contrast with previous studies, where formation of the benzyl cation was suggested to occur from the neutral benzyl alcohol through the Lewis acid action of excited TPP+ (TPP*).

Branchi, B., Bietti, M., Ercolani, G., Angeles Izquierdo, M., Miranda, M., Stella, L. (2004). The role of aromatic radical cations and benzylic cations in the 2,4,6-triphenylpyrylium tetrafluoroborate photosensitized oxidation of ring-methoxylated benzyl alcohols in CH2Cl2 solution. JOURNAL OF ORGANIC CHEMISTRY, 69(25), 8874-8885 [10.1021/jo048546h].

The role of aromatic radical cations and benzylic cations in the 2,4,6-triphenylpyrylium tetrafluoroborate photosensitized oxidation of ring-methoxylated benzyl alcohols in CH2Cl2 solution

BIETTI, MASSIMO;ERCOLANI, GIANFRANCO;STELLA, LORENZO
2004-01-01

Abstract

A steady-state and laser flash photolysis (LFP) study of the TPPBF 4-photosensitized oxidation of ring-methoxylated benzyl alcohols has been carried out. Direct evidence on the involvement of intermediate benzyl alcohol radical cations and benzylic cations in these reactions has been provided through LFP experiments. The reactions lead to the formation of products (benzaldehydes, dibenzyl ethers, and diphenylmethanes) whose amounts and distributions are influenced by the number and relative position of the methoxy substituents. This behavior has been rationalized in terms of the interplay between the stabilities of benzyl alcohol radical cations and benzyl cations involved in these processes. A general mechanism for the TPPBF 4-photosensitized reactions of ring-methoxylated benzyl alcohols has been proposed, where the a-OH group of the parent substrate acts as the deprotonating base promoting α-C-H deprotonation of the benzyl alcohol radical cation (formed after electron transfer from the benzyl alcohol to TPP*) to give a benzyl radical and a protonated benzyl alcohol, precursor of the benzylic cation. This hypothesis is in contrast with previous studies, where formation of the benzyl cation was suggested to occur from the neutral benzyl alcohol through the Lewis acid action of excited TPP+ (TPP*).
Pubblicato
Rilevanza internazionale
Articolo
Sì, ma tipo non specificato
Settore CHIM/06 - Chimica Organica
English
Con Impact Factor ISI
Aromatic compounds; Oxidation; Photolysis; Positive ions; Benzylic cations; Radical cations; Alcohols; 2,4,6 triphenylpyrylium tetrafluoroborate; aromatic compound; benzyl alcohol; cation; photosensitizing agent; pyridine derivative; radical; unclassified drug; absorption spectroscopy; article; chemical reaction; chemical structure; density functional theory; fluorescence; gas chromatography; irradiation; laser; laser flash photolysis; light; mass spectrometry; oxidation; photolysis; photosensitization; proton nuclear magnetic resonance; Benzyl Alcohol; Borates; Cations; Fluorescence; Free Radicals; Hydrocarbons, Aromatic; Lasers; Methylene Chloride; Molecular Structure; Oxidation-Reduction; Photochemistry; Photolysis; Pyrans; Solutions
Branchi, B., Bietti, M., Ercolani, G., Angeles Izquierdo, M., Miranda, M., Stella, L. (2004). The role of aromatic radical cations and benzylic cations in the 2,4,6-triphenylpyrylium tetrafluoroborate photosensitized oxidation of ring-methoxylated benzyl alcohols in CH2Cl2 solution. JOURNAL OF ORGANIC CHEMISTRY, 69(25), 8874-8885 [10.1021/jo048546h].
Branchi, B; Bietti, M; Ercolani, G; Angeles Izquierdo, M; Miranda, M; Stella, L
Articolo su rivista
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/33101
Citazioni
  • ???jsp.display-item.citation.pmc??? 1
  • Scopus ND
  • ???jsp.display-item.citation.isi??? 24
social impact