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Paper | Regular issue | Vol 55, No. 2, 2001, pp.331-351
Published online, 1st January, 1970
DOI: 10.3987/COM-00-9102
Scope and Limitations in the Regioselective Synthesis of 1,3,5-Trisubstituted Pyrazoles from β-Amino Enones and Hydrazine Derivatives. 13C-Chemical Shift Prediction Rules for 1,3,5-Trisubstituted Pyrazoles

Angel Alberola, Luis Calvo Bleye, Alfonso González-Ortega,* M. Luisa Sádaba, and M. Carmen Sañudo

*Deparamento de Química Orgánica, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid, Spain

Abstract

β-amino enones react with hydrazine derivatives to give regioselectively 1,3,5-trisubstituted pyrazoles. The synthetic method only presents limitations when the β-substituent of the enone and the hydrazine substituent are bulky or possess an electron withdrawing character. Comparison of the 13C-NMR spectra of the seventy pyrazoles allowed us to estimate a 13C-chemical shift prediction rule for 1,3,5-trisubstituted pyrazoles, with deviations of less than ± 1 ppm.