Regioselective N‑Addition/Substitution Reaction of α‑Alkylidene Pyrazolinones with Propargyl Sulfonium Salts to Construct Allylthio-Containing Pyrazolones

The regioselective N-addition/substitution
reaction between α-alkylidene
pyrazolinones and propargyl sulfonium salts has been developed to
construct functionalized allylthio-containing pyrazolones with moderate
to excellent yields. α-Alkylidene pyrazolinones act as N-nucleophilic
agents which are distinguished from reported C-nucleophilic reactions.
Excellent regioselectivity, readily available starting materials,
the broad range of substrates, gram-scale synthesis, and simple operation
illustrate the synthetic advantages of this new reaction pathway.