Nitration of 3,5-dinitropyrazole with HNO3–H2SO4 mixture gives 3,4,5-trinitro-1H-pyrazole, which in reaction with ammonia, amines or thiols under mild conditions undergoes regioselective nucleophilic substitution of the 4-positioned nitro group.
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Dalinger et al. (2010) studied this question.
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