A synthesis of tetrasubstituted pyrazoles containing two, three or four pyridinyl substituents is described. Hence, the reaction of 1,3-dipyridinyl-1,3-propanediones with 2-hydrazinopyridine or phenylhydrazine, respectively, affords the corresponding 1,3,5-trisubstituted pyrazoles. Iodination at the 4-position of the pyrazole nucleus by treatment with I2/HIO3 gives the appropriate 4-iodopyrazoles which served as starting materials for different cross-coupling reactions. Finally, Negishi cross-coupling employing organozinc halides and Pd catalysts turned out to be the method of choice to obtain the desired tetrasubstituted pyrazoles. The formation of different unexpected reaction products is described. Detailed NMR spectroscopic investigations (1H, 13C, 15N) were undertaken with all products prepared. Moreover, the structure of a condensation product was confirmed by crystal structure analysis.

Synthesis of tetrasubstituted pyrazoles containing pyridinyl substituents / J. Jansa, R. Schmidt, A.D. Mamuye, L. Castoldi, A. Roller, V. Pace, W. Holzer. - In: BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY. - ISSN 1860-5397. - 13(2017 May 12), pp. 895-902. [10.3762/bjoc.13.90]

Synthesis of tetrasubstituted pyrazoles containing pyridinyl substituents

L. Castoldi;
2017

Abstract

A synthesis of tetrasubstituted pyrazoles containing two, three or four pyridinyl substituents is described. Hence, the reaction of 1,3-dipyridinyl-1,3-propanediones with 2-hydrazinopyridine or phenylhydrazine, respectively, affords the corresponding 1,3,5-trisubstituted pyrazoles. Iodination at the 4-position of the pyrazole nucleus by treatment with I2/HIO3 gives the appropriate 4-iodopyrazoles which served as starting materials for different cross-coupling reactions. Finally, Negishi cross-coupling employing organozinc halides and Pd catalysts turned out to be the method of choice to obtain the desired tetrasubstituted pyrazoles. The formation of different unexpected reaction products is described. Detailed NMR spectroscopic investigations (1H, 13C, 15N) were undertaken with all products prepared. Moreover, the structure of a condensation product was confirmed by crystal structure analysis.
Negishi coupling; NMR (1H,; 13; C,; 15; N); Pyrazole; Pyridine; X-ray structure analysis
Settore CHIM/06 - Chimica Organica
Article (author)
File in questo prodotto:
File Dimensione Formato  
1860-5397-13-90.pdf

accesso aperto

Tipologia: Publisher's version/PDF
Dimensione 402.83 kB
Formato Adobe PDF
402.83 kB Adobe PDF Visualizza/Apri
Pubblicazioni consigliate

Caricamento pubblicazioni consigliate

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/2434/890717
Citazioni
  • ???jsp.display-item.citation.pmc??? 2
  • Scopus 6
  • ???jsp.display-item.citation.isi??? 6
social impact