Synthetic routes to 3(5)-phosphonylated pyrazoles

This review comprehensively covers the currently available synthetic routes to 3(5)-phosphonylated pyrazoles. There are demonstrated significant advances in this field over the last 10–15 years caused by the use of the Bestmann–Ohira reagent [as well as (diazomethyl)phosphonates and phosphonylated hydrazonoyl halides] in reactions with diverse dipolarophiles. 1,3-Dipolar cycloaddition of diazo compounds to $\alpha$,$\beta$-unsaturated phosphonates as well as intramolecular heterocyclization of (1-diazoallyl)phosphonates and (3-diazo-1-propenyl)phosphonates are discussed. Synthetic potential of cyclocondensation of organophosphorus 1,3-dielectrophilic compounds with hydrazines is shown. Ways to introduce a phosphonate group into the pyrazole ring are considered. Examples of chemical transformations of 3(5)-phosphonylated pyrazoles are reported.
The bibliography includes 88 references.