NMR study of the (Z)-phenylhydrazones of 5-alkyl- and 5-aryl-3-benzoyl-1,2,4-oxadiazoles: support for the interpretation of kinetic results on the rearrangement of 1,2,4-oxadiazoles to 1,2,3-triazoles

Liliana Lamartina, Gabriella Macaluso, Francesca D'Anna, Vincenzo Frenna, Elisabetta Mezzina, Domenico Spinelli

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3 Citazioni (Scopus)

Abstract

An analysis of the 1H, 13C, and 15N NMR substituent chemicalshifts (SCSs) of the title compounds in CDCl3 solution hasbeen carried out by using the SCSs of other classes of compounds(arenes, methyl esters or amides), Hammett substituentconstants or kinetic data. The results obtained provideinformation concerning the ground-state electronic distributionof the compounds examined. The results relevant to thecarbon and nitrogen atoms of the 1,2,4-oxadiazole ring canbe considered of special interest, as the effects of the substit-IntroductionFor several years our research group has been involvedin the use of NMR spectroscopic data (1H, 13C, 15N, and17O) to obtain information about the ground-state electronicdistribution of different classes of organic compoundsand to evaluate the influence of substituents on thisdistribution in order to correlate NMR and reactivitydata.[1,2]Thus, the study of the SCSs (substituent-induced chemicalshifts) of aryl (or heteroaryl) carboxylic acids[1a–1c] andtheir derivatives (esters[1d–1g] and amides[1f]) or ketones,[1d,1i]arylhydrazines[2a–2c] or (Z)-arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole[2d] by using both the one- and thetwo-parameter [DSP (dual substituent parameter)] treatment,has furnished free-energy relationships (FERs) thatare useful for an analysis of substituent effects.At the same time, we have deeply investigated the mechanismsof the “monocyclic rearrangement of heterocycles”(MRH or Boulton–Katritzky reaction, BKR)[3] by collect-[a] Dipartimento di Chimica Organica “A. Mangini”, Universitàdi Bologna,Via San Giacomo 11, 40126 Bologna, ItalyFax: + 39-051-209-5688E-mail: domenico.spinelli@unibo.it[b] Dipartimento di Chimica e Tecnologie Farmaceutiche, Universitàdi Palermo,Via Archirafi 32, 90123 Palermo, Italy[c] Dipartimento di Chimica Organica “E. Paternò”, Università diPalermo,Viale delle Scienze, Parco d’Orleans II, 90128 Palermo, Italy© 2005 Wiley-VCH Verlag GmbH & Co. 3980 KGaA, Weinheim DOI: 10.1002/ejoc.200500236 Eur. J. Org. Chem. 2005, 3980–3986uents on the chemical shifts of N-4 and C-5 appear in linewith kinetic results collected in the study of the rearrangement(Boulton–Katritzky reaction) of the title compounds intothe relevant 1,2,3-triazoles, thereby strongly supporting theimportance of the leaving-group ability of the N-4/C-5/O-1system.
Lingua originaleEnglish
pagine (da-a)3980-3986
Numero di pagine7
RivistaEuropean Journal of Organic Chemistry
Volume2005
Stato di pubblicazionePublished - 2005

All Science Journal Classification (ASJC) codes

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