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Chapter 3
Synthesis of trisubstituted pyrazoles/isoxazoles
Alex F. C. Flores et al. 35 have been synthesized a new series of hydroxyl
pyrazoles and 2-methyl-3-isoxazolones from the cyclocondensation reaction of
trichloromethyl-substituted 1,3-dielectrophiles with dry hydrazine and N-methyl
hydroxylamine respectively (Figure-18).
Figure-18
Sarvesh Kumar et al. 36 has synthesized pyrazole and isoxazole derivatives via
hetero annulations of 10,11-Dihydro-11-[bis(methylthio)methylene]dibenzoxepin-10-
one (α-oxoketene dithioacetal) (Figure-19).
Figure-19
Valentina Molteni et al. 37 have been developed an extremely simple one pot
reaction for transforming diketones into the corresponding pyrazoles and isoxazoles
promoted by microwave irradiation (Figure-20).
O
O
O
H 3 CO OCH
R-NHNH 3
2
NH 2 OH
n N
n n N
N MW H 2 O
N
MW
O
O
R
n= 0, 1, 2
Figure-20
Thomas Kurz et al. 38 has synthesized novel fluorinated ketene N,S-acetals
were readily prepared by the reaction of fluorosubstituted cyanoacetamide derivatives
with arylisothiocyanate in the presence of potassium hydroxide, followed by the
alkylation of the produced salts with methyl iodide. The reaction of fluorinated ketene
N,S-acetals with hydrazine afforded different fluorosubstituted pyrazole (Figure-21).
Department of Chemistry Saurashtra university, Rajkot-360005 91