Resumen

BELMAR, J.; ALDERETE, J.; PARRA, M.  y  ZUNIGA, C.. SYNTHESIS AND TAUTOMERISM OF NEW 1-n-ALKYL-5-PYRAZOLONE DERIVATIVES. Bol. Soc. Chil. Quím. [online]. 1999, vol.44, n.3, pp. 367-374. ISSN 0366-1644.  http://dx.doi.org/10.4067/S0366-16441999000300014.

3-Phenyl-5-pyrazolone (1) is selectively alkylated at position 1 in 40% yield. The alkylated compound (2) is acylated (3) in 60% yield and nitrosated (4) in 80% yield. According to the spectroscopic data a N-H or O-H structure can be proposed for 1 in DMSO. The proton may be at N-2 or on the oxygen at C-5, respectively. The alkylated compound 2 exists as 5-pyrazolone in chloroform with a CH₂ at C-4. In DMSO, 2 is a 5-hydroxypyrazole. For compound 3 in chloroform the structure corresponds to 4-acyl-5-hydroxypyrazole. For compound 4 in chloroform there is one tautomer with a 4-nitroso-5-hydroxypyrazole structure while in DMSO the same 4-nitroso-5-hydroxypyrazole (92%) and a 4-nitroso-5-pyrazolone (8%) tautomer can be found

Palabras llave : Tautomerism; alkylpyrazolones; pyrazolones; chelating pyrazolones; synthesis.