A preparative method of N-amination of pyrazoles bearing nitro groups
and other electron withdrawing substituents in the pyrazole ring with
hydroxylamine-O-sulfonic acid involving control of the pH of the mediu
m has been elaborated. A series of previously unknown pyrazoles has be
en prepared. Basicities (pK(BH+)) of 1-aminopyrazole and 1-amino-4-nit
ropyrazole have been measured and differences between the basicities o
f the C- and N-amino groups for the pyrazole series have been revealed
.