Dimethyl Diazomethylphosphonate

One-Pot, Two-Step Conversion of Aldehydes to Phosphonyl- and Sulfonylpyrazoles Using Bestmann–Ohira Reagent

“…The new role played by BOR 3a as a 1,3-dipole precursor, besides its traditional role as a Horner–Wadsworth–Emmons (HWE) reagent in the one-pot conversion of aldehydes 1 to acetylenes 6 , appeared to have further scope in the development of novel synthetic methods. Interestingly, in both reactions, the proposed species is diethyl diazomethylphosphonate (Seyferth–Colvin–Gilbert reagent) anion, which is generated in situ by a nucleophilic base. Therefore, we embarked on the idea of exploiting the dual reactivity of BOR 3a in the single-pot transformation of aldehydes 1 to phosphonylpyrazoles 7 (Scheme b).…”