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Volume 13 (1997), Issue 2, Pages 113-123

Azapentalenes. XLIV. 1H and 13C-NMR study of mesoionic pyrazolo[1,2-a]pyrazoles

Rosa María Claramunt,1 Sviatoslav Trofimenko,2 Isabel Rozas,3 and José Elguero3

1Departamento de Química Orgánica y Biología, UNED, Senda del Rey, s/n, E-28040 Madrid, Spain
2Du Pont Central Research and Development, Experimental Station, Wilmington, DE 19880-0302, USA
3Instituto de Química Médica, CSIC, Juan de la Cierva 3, E-28006 Madrid, Spain

Received 3 January 1996; Revised 12 March 1996

Copyright © 1997 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The 1H and 13C chemical shifts as well as the 1H–1H and 1H–13C coupling constants of sixteen pyrazolo[1,2-a]pyrazole derivatives have been measured. The most relevant features are discussed using resonance forms and simple additive models. AM1 semi-empirical calculations have been carried out to provide a rationale for the NMR results.