Catalytic Trimerization of Bis-silylated Diazomethane

摘要

(Me_3Si)_2CNN isomerizes upon addition of traces of [Me_3Si]~+ ions to give (Me_3Si)_2NNC, which then undergoes an unusual trimerization reaction to give exclusively 4-diazenyl-3-hydrazinylpyrazole. As catalyst the isonitrilium ion, [(Me_3Si)_2NNC-(SiMe_3)]~+, was identified and fully characterized. Experiments and computations indicate a three-step reaction including isomerization of diazomethane, a C-C or N-C coupling, and a formal cycloaddition reaction. The kinetics and thermodynamics are discussed on the basis of DFT calculations.