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Construction of 3,4-Disubstituted-3-(difluoromethyl)pyrazoles

Abstract The CHF2 moiety has been widely utilized in the design of pharmaceuticals and agrochemicals, because this group can act as hydrogen-bonding donor to improve the binding selectivity of biologically active compounds, as a bioisostere to substitute for methyl, methoxy, hydroxy, amino and thiol groups, and as a lipophilic regulator to improve the liposolubility of the active compounds. For example, 3-difluoromethylpyrazole scaffolds are present in many organic compounds that exhibit important biological activities. In this content, there are nearly ten kinds of pesticide molecules on the market that contain 3,4-disubstituted-3-(difluoromethyl)pyrazole units, with annual sales of up to one billion dollars. In this review, the methods of construction of 3,4-disubstituted 3-difluoromethylpyrazoles will been briefly summarized that have been reported so far. Four different strategies including using fluorinated reagents as substrates, difluoroacetic acid and its derivatives as fluorine building blocks, difluorodiazonium and others as fluorine building blocks will be introduced.