Co-II-porphyrin complexes catalyze the reaction of aromatic azides (ArN3) with hydrocarbons that contain a benzylic group ((ArRRCH)-R-1-C-2) to give the corresponding amines ((ArRRC)-R-1-C-2-N-HAr). When at least one of the R substituents is hydrogen, the catalytic reaction proceeds further to give the imine ArRC=NAr in good yields. The reaction mechanism has been investigated. The reaction proceeds through a reversible coordination of the arylazide to the Co-II-porphyrin complex. This unstable adduct can either react with the hydrocarbon in the rate-determining step or decompose by a unimolecular mechanism to afford a putative "nitrene" complex, which reacts with more azide, but not with the hydrocarbon, to afford the byproduct diaryldiazene. The kinetics of the catalytic reaction have been investigated for a range of azides and substituted toluenes. Arylazides with electron-withdrawing substituents react at a faster rate and a good correlation is found between the log(k) and the Taft parameters. On the other hand, an excellent correlation between the logarithm of the rate for substituted toluenes relative to that of toluene and a radical parameter (sigma(JJ)) alone was found, with no significant contribution by polar parameters. An explanation has been proposed for this anomalous effect and for the very high isotopic effect (k(H)/k(D) = 14) found.
Amination of benzylic C-H bonds by arylazides catalyzed by Co-II-porphyrin complexes: A synthetic and mechanistic study / F. Ragaini, A. Penoni, E. Gallo, S. Tollari, C. Gotti, M. Lapadula, E. Mangioni, S. Cenini. - In: CHEMISTRY-A EUROPEAN JOURNAL. - ISSN 0947-6539. - 9:1(2003), pp. 249-259. [10.1002/chem.200390018]
Amination of benzylic C-H bonds by arylazides catalyzed by Co-II-porphyrin complexes: A synthetic and mechanistic study
F. RagainiPrimo
;E. Gallo;S. Tollari;S. CeniniUltimo
2003
Abstract
Co-II-porphyrin complexes catalyze the reaction of aromatic azides (ArN3) with hydrocarbons that contain a benzylic group ((ArRRCH)-R-1-C-2) to give the corresponding amines ((ArRRC)-R-1-C-2-N-HAr). When at least one of the R substituents is hydrogen, the catalytic reaction proceeds further to give the imine ArRC=NAr in good yields. The reaction mechanism has been investigated. The reaction proceeds through a reversible coordination of the arylazide to the Co-II-porphyrin complex. This unstable adduct can either react with the hydrocarbon in the rate-determining step or decompose by a unimolecular mechanism to afford a putative "nitrene" complex, which reacts with more azide, but not with the hydrocarbon, to afford the byproduct diaryldiazene. The kinetics of the catalytic reaction have been investigated for a range of azides and substituted toluenes. Arylazides with electron-withdrawing substituents react at a faster rate and a good correlation is found between the log(k) and the Taft parameters. On the other hand, an excellent correlation between the logarithm of the rate for substituted toluenes relative to that of toluene and a radical parameter (sigma(JJ)) alone was found, with no significant contribution by polar parameters. An explanation has been proposed for this anomalous effect and for the very high isotopic effect (k(H)/k(D) = 14) found.File | Dimensione | Formato | |
---|---|---|---|
23) CoBenz2.pdf
accesso riservato
Tipologia:
Publisher's version/PDF
Dimensione
198.36 kB
Formato
Adobe PDF
|
198.36 kB | Adobe PDF | Visualizza/Apri Richiedi una copia |
Pubblicazioni consigliate
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.